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Puzzled by Adams, K factor and middle grey
Puzzled by Adams, K factor and middle grey
When re-reading Ansel Adams' "The Negative", I came across by the
following paragraph, which appears on pp. 42-43 in the 2002 editions,
whivh I belive is a reprint of the 1981 edition:
'If pressed, the manufacturers of some exposure meters will
acknowledge that they depart from standard calibration of their
meters by incorporating a "K factor." This factor is supposed to
give a higher percentage of acceptable images under average
conditions than a meter calibrated exactly to an 18 percent
reflectance. The practical effect of the K factor is that if we
make a careful reading from a middle-gray surface and expose as
indicated, the result will not be exactly a middle gray!'
So far so good. This just indicates that the master also was aware
of the same thing that Thom Hogan and others have observed, that
"meters don't see 18% gray" ( * w w w .bythom . com /graycards.htm ).
However, Adams goes om to say:
With nearly all meters, this factor is equivalent to giving a
one-third stop /increase/ in exposure.
And it is not just a typo, on pp. 66-67 in the same book, Adams
suggest that the photographer compensate for the K-factor upping the
ASA dialed in the meter. By example, he said tha one should set ASA 80
on the meter when shooting ASA 64 film. This, of course has the same
effect as adjusting exposure by -1/3 EV.
The reason I am puzzled by this, is because careful metering of
a Kodak 18% grey card with a Sekonic L-778 spot meter confirms
that the meter doesn't see 18% grey, but the offset result in
about 1/2 stop /decrease/ in exposure, not an /increase/ as
suggested by Adams. (I've checked this with other meters,
and while readings differ by about +-1/6 EV, they all show a
decrease with respect to a reading that would have placed
the card at middle gray.
And indeed, the instructions that came with my Kodak grey card said:
For subjects of normal reflectance increase the indicated exposure
by 1/2 stop.
Kodak's instructions fits my observations exactly
(if "normal reflectance" = "18% grey").
So ...
To me it looks like Adams somehow managed to get the bit about
teh K Factor backwards.
The reason I am posting this here is basically to get some
second opinions on this. Did the great one bungle this particular
detail, or is there something that I've misunderstood?
--
- gisle hannemyr [ gisle{at}hannemyr.no - * hannemyr . com /photo/ ]
------------------------------------------------------------------------
Sigma SD10, Kodak DCS460, Canon Powershot G5, Olympus 2020Z
------------------------------------------------------------------------
When re-reading Ansel Adams' "The Negative", I came across by the
following paragraph, which appears on pp. 42-43 in the 2002 editions,
whivh I belive is a reprint of the 1981 edition:
'If pressed, the manufacturers of some exposure meters will
acknowledge that they depart from standard calibration of their
meters by incorporating a "K factor." This factor is supposed to
give a higher percentage of acceptable images under average
conditions than a meter calibrated exactly to an 18 percent
reflectance. The practical effect of the K factor is that if we
make a careful reading from a middle-gray surface and expose as
indicated, the result will not be exactly a middle gray!'
So far so good. This just indicates that the master also was aware
of the same thing that Thom Hogan and others have observed, that
"meters don't see 18% gray" ( * w w w .bythom . com /graycards.htm ).
However, Adams goes om to say:
With nearly all meters, this factor is equivalent to giving a
one-third stop /increase/ in exposure.
And it is not just a typo, on pp. 66-67 in the same book, Adams
suggest that the photographer compensate for the K-factor upping the
ASA dialed in the meter. By example, he said tha one should set ASA 80
on the meter when shooting ASA 64 film. This, of course has the same
effect as adjusting exposure by -1/3 EV.
The reason I am puzzled by this, is because careful metering of
a Kodak 18% grey card with a Sekonic L-778 spot meter confirms
that the meter doesn't see 18% grey, but the offset result in
about 1/2 stop /decrease/ in exposure, not an /increase/ as
suggested by Adams. (I've checked this with other meters,
and while readings differ by about +-1/6 EV, they all show a
decrease with respect to a reading that would have placed
the card at middle gray.
And indeed, the instructions that came with my Kodak grey card said:
For subjects of normal reflectance increase the indicated exposure
by 1/2 stop.
Kodak's instructions fits my observations exactly
(if "normal reflectance" = "18% grey").
So ...
To me it looks like Adams somehow managed to get the bit about
teh K Factor backwards.
The reason I am posting this here is basically to get some
second opinions on this. Did the great one bungle this particular
detail, or is there something that I've misunderstood?
--
- gisle hannemyr [ gisle{at}hannemyr.no - * hannemyr . com /photo/ ]
------------------------------------------------------------------------
Sigma SD10, Kodak DCS460, Canon Powershot G5, Olympus 2020Z
------------------------------------------------------------------------
Re: Puzzled by Adams, K factor and middle grey
"Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
news:q5tzvp7f7v.fsf@kaksi.ifi.uio.no...
> When re-reading Ansel Adams' "The Negative", I came across by the
> following paragraph, which appears on pp. 42-43 in the 2002 editions,
> whivh I belive is a reprint of the 1981 edition:
>
> 'If pressed, the manufacturers of some exposure meters will
> acknowledge that they depart from standard calibration of their
> meters by incorporating a "K factor." This factor is supposed to
> give a higher percentage of acceptable images under average
> conditions than a meter calibrated exactly to an 18 percent
> reflectance. The practical effect of the K factor is that if we
> make a careful reading from a middle-gray surface and expose as
> indicated, the result will not be exactly a middle gray!'
>
> So far so good. This just indicates that the master also was aware
> of the same thing that Thom Hogan and others have observed, that
> "meters don't see 18% gray" ( * w w w .bythom . com /graycards.htm ).
>
> However, Adams goes om to say:
>
> With nearly all meters, this factor is equivalent to giving a
> one-third stop /increase/ in exposure.
>
> And it is not just a typo, on pp. 66-67 in the same book, Adams
> suggest that the photographer compensate for the K-factor upping the
> ASA dialed in the meter. By example, he said tha one should set ASA 80
> on the meter when shooting ASA 64 film. This, of course has the same
> effect as adjusting exposure by -1/3 EV.
>
> The reason I am puzzled by this, is because careful metering of
> a Kodak 18% grey card with a Sekonic L-778 spot meter confirms
> that the meter doesn't see 18% grey, but the offset result in
> about 1/2 stop /decrease/ in exposure, not an /increase/ as
> suggested by Adams. (I've checked this with other meters,
> and while readings differ by about +-1/6 EV, they all show a
> decrease with respect to a reading that would have placed
> the card at middle gray.
>
> And indeed, the instructions that came with my Kodak grey card said:
>
> For subjects of normal reflectance increase the indicated exposure
> by 1/2 stop.
>
> Kodak's instructions fits my observations exactly
> (if "normal reflectance" = "18% grey").
if you meter a gray card and it shows that it is 1/3 below 18%, when it
should be 18% then to bring it up to 18% gray you need to increase it.
Robert
"Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
news:q5tzvp7f7v.fsf@kaksi.ifi.uio.no...
> When re-reading Ansel Adams' "The Negative", I came across by the
> following paragraph, which appears on pp. 42-43 in the 2002 editions,
> whivh I belive is a reprint of the 1981 edition:
>
> 'If pressed, the manufacturers of some exposure meters will
> acknowledge that they depart from standard calibration of their
> meters by incorporating a "K factor." This factor is supposed to
> give a higher percentage of acceptable images under average
> conditions than a meter calibrated exactly to an 18 percent
> reflectance. The practical effect of the K factor is that if we
> make a careful reading from a middle-gray surface and expose as
> indicated, the result will not be exactly a middle gray!'
>
> So far so good. This just indicates that the master also was aware
> of the same thing that Thom Hogan and others have observed, that
> "meters don't see 18% gray" ( * w w w .bythom . com /graycards.htm ).
>
> However, Adams goes om to say:
>
> With nearly all meters, this factor is equivalent to giving a
> one-third stop /increase/ in exposure.
>
> And it is not just a typo, on pp. 66-67 in the same book, Adams
> suggest that the photographer compensate for the K-factor upping the
> ASA dialed in the meter. By example, he said tha one should set ASA 80
> on the meter when shooting ASA 64 film. This, of course has the same
> effect as adjusting exposure by -1/3 EV.
>
> The reason I am puzzled by this, is because careful metering of
> a Kodak 18% grey card with a Sekonic L-778 spot meter confirms
> that the meter doesn't see 18% grey, but the offset result in
> about 1/2 stop /decrease/ in exposure, not an /increase/ as
> suggested by Adams. (I've checked this with other meters,
> and while readings differ by about +-1/6 EV, they all show a
> decrease with respect to a reading that would have placed
> the card at middle gray.
>
> And indeed, the instructions that came with my Kodak grey card said:
>
> For subjects of normal reflectance increase the indicated exposure
> by 1/2 stop.
>
> Kodak's instructions fits my observations exactly
> (if "normal reflectance" = "18% grey").
if you meter a gray card and it shows that it is 1/3 below 18%, when it
should be 18% then to bring it up to 18% gray you need to increase it.
Robert
Re: Puzzled by Adams, K factor and middle grey
"Robert" <rac2901spam@spamsbcglobal . net > writes:
> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
>> When re-reading Ansel Adams' "The Negative", I came across by the
>> following paragraph, which appears on pp. 42-43 in the 2002 editions,
>> whivh I belive is a reprint of the 1981 edition:
>>
>> 'If pressed, the manufacturers of some exposure meters will
>> acknowledge that they depart from standard calibration of their
>> meters by incorporating a "K factor." This factor is supposed to
>> give a higher percentage of acceptable images under average
>> conditions than a meter calibrated exactly to an 18 percent
>> reflectance. The practical effect of the K factor is that if we
>> make a careful reading from a middle-gray surface and expose as
>> indicated, the result will not be exactly a middle gray!'
>>
>> So far so good. This just indicates that the master also was aware
>> of the same thing that Thom Hogan and others have observed, that
>> "meters don't see 18% gray" ( * w w w .bythom . com /graycards.htm ).
>>
>> However, Adams goes om to say:
>>
>> With nearly all meters, this factor is equivalent to giving a
>> one-third stop /increase/ in exposure.
>>
>> And it is not just a typo, on pp. 66-67 in the same book, Adams
>> suggest that the photographer compensate for the K-factor upping the
>> ASA dialed in the meter. By example, he said tha one should set ASA 80
>> on the meter when shooting ASA 64 film. This, of course has the same
>> effect as adjusting exposure by -1/3 EV.
>>
>> The reason I am puzzled by this, is because careful metering of
>> a Kodak 18% grey card with a Sekonic L-778 spot meter confirms
>> that the meter doesn't see 18% grey, but the offset result in
>> about 1/2 stop /decrease/ in exposure, not an /increase/ as
>> suggested by Adams. (I've checked this with other meters,
>> and while readings differ by about +-1/6 EV, they all show a
>> decrease with respect to a reading that would have placed
>> the card at middle gray.
>>
>> And indeed, the instructions that came with my Kodak grey card said:
>>
>> For subjects of normal reflectance increase the indicated exposure
>> by 1/2 stop.
>>
>> Kodak's instructions fits my observations exactly
>> (if "normal reflectance" = "18% grey").
> if you meter a gray card and it shows that it is 1/3 below 18%, when
> it should be 18% then to bring it up to 18% gray you need to
> increase it.
So you agree that the information in "The Negative" is wrong on
this particular point?
--
- gisle hannemyr [ gisle{at}hannemyr.no - * hannemyr . com /photo/ ]
------------------------------------------------------------------------
Sigma SD10, Kodak DCS460, Canon Powershot G5, Olympus 2020Z
------------------------------------------------------------------------
"Robert" <rac2901spam@spamsbcglobal . net > writes:
> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
>> When re-reading Ansel Adams' "The Negative", I came across by the
>> following paragraph, which appears on pp. 42-43 in the 2002 editions,
>> whivh I belive is a reprint of the 1981 edition:
>>
>> 'If pressed, the manufacturers of some exposure meters will
>> acknowledge that they depart from standard calibration of their
>> meters by incorporating a "K factor." This factor is supposed to
>> give a higher percentage of acceptable images under average
>> conditions than a meter calibrated exactly to an 18 percent
>> reflectance. The practical effect of the K factor is that if we
>> make a careful reading from a middle-gray surface and expose as
>> indicated, the result will not be exactly a middle gray!'
>>
>> So far so good. This just indicates that the master also was aware
>> of the same thing that Thom Hogan and others have observed, that
>> "meters don't see 18% gray" ( * w w w .bythom . com /graycards.htm ).
>>
>> However, Adams goes om to say:
>>
>> With nearly all meters, this factor is equivalent to giving a
>> one-third stop /increase/ in exposure.
>>
>> And it is not just a typo, on pp. 66-67 in the same book, Adams
>> suggest that the photographer compensate for the K-factor upping the
>> ASA dialed in the meter. By example, he said tha one should set ASA 80
>> on the meter when shooting ASA 64 film. This, of course has the same
>> effect as adjusting exposure by -1/3 EV.
>>
>> The reason I am puzzled by this, is because careful metering of
>> a Kodak 18% grey card with a Sekonic L-778 spot meter confirms
>> that the meter doesn't see 18% grey, but the offset result in
>> about 1/2 stop /decrease/ in exposure, not an /increase/ as
>> suggested by Adams. (I've checked this with other meters,
>> and while readings differ by about +-1/6 EV, they all show a
>> decrease with respect to a reading that would have placed
>> the card at middle gray.
>>
>> And indeed, the instructions that came with my Kodak grey card said:
>>
>> For subjects of normal reflectance increase the indicated exposure
>> by 1/2 stop.
>>
>> Kodak's instructions fits my observations exactly
>> (if "normal reflectance" = "18% grey").
> if you meter a gray card and it shows that it is 1/3 below 18%, when
> it should be 18% then to bring it up to 18% gray you need to
> increase it.
So you agree that the information in "The Negative" is wrong on
this particular point?
--
- gisle hannemyr [ gisle{at}hannemyr.no - * hannemyr . com /photo/ ]
------------------------------------------------------------------------
Sigma SD10, Kodak DCS460, Canon Powershot G5, Olympus 2020Z
------------------------------------------------------------------------
Re: Puzzled by Adams, K factor and middle grey
"Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
news:q5ejmt4d01.fsf@honbori.ifi.uio.no...
> "Robert" <rac2901spam@spamsbcglobal . net > writes:
>> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
>
>>> When re-reading Ansel Adams' "The Negative", I came across by the
>>> following paragraph, which appears on pp. 42-43 in the 2002 editions,
>>> whivh I belive is a reprint of the 1981 edition:
>>>
>>> 'If pressed, the manufacturers of some exposure meters will
>>> acknowledge that they depart from standard calibration of their
>>> meters by incorporating a "K factor." This factor is supposed to
>>> give a higher percentage of acceptable images under average
>>> conditions than a meter calibrated exactly to an 18 percent
>>> reflectance. The practical effect of the K factor is that if we
>>> make a careful reading from a middle-gray surface and expose as
>>> indicated, the result will not be exactly a middle gray!'
>>>
>>> So far so good. This just indicates that the master also was aware
>>> of the same thing that Thom Hogan and others have observed, that
>>> "meters don't see 18% gray" ( * w w w .bythom . com /graycards.htm ).
>>>
>>> However, Adams goes om to say:
>>>
>>> With nearly all meters, this factor is equivalent to giving a
>>> one-third stop /increase/ in exposure.
>>>
>>> And it is not just a typo, on pp. 66-67 in the same book, Adams
>>> suggest that the photographer compensate for the K-factor upping the
>>> ASA dialed in the meter. By example, he said tha one should set ASA 80
>>> on the meter when shooting ASA 64 film. This, of course has the same
>>> effect as adjusting exposure by -1/3 EV.
>>>
>>> The reason I am puzzled by this, is because careful metering of
>>> a Kodak 18% grey card with a Sekonic L-778 spot meter confirms
>>> that the meter doesn't see 18% grey, but the offset result in
>>> about 1/2 stop /decrease/ in exposure, not an /increase/ as
>>> suggested by Adams. (I've checked this with other meters,
>>> and while readings differ by about +-1/6 EV, they all show a
>>> decrease with respect to a reading that would have placed
>>> the card at middle gray.
>>>
>>> And indeed, the instructions that came with my Kodak grey card said:
>>>
>>> For subjects of normal reflectance increase the indicated exposure
>>> by 1/2 stop.
>>>
>>> Kodak's instructions fits my observations exactly
>>> (if "normal reflectance" = "18% grey").
>
>> if you meter a gray card and it shows that it is 1/3 below 18%, when
>> it should be 18% then to bring it up to 18% gray you need to
>> increase it.
>
> So you agree that the information in "The Negative" is wrong on
> this particular point?
> --
No it is correct.
lets say you have a measuring cup that should hold 1 cup of water but you
test it and it only comes up 2/3 cup to compensate for the difference you
add an extra 1/3 cup so it will have a full cup. to off site the lower meter
reading you have to add the difference to equal the right amount.
Robert
"Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
news:q5ejmt4d01.fsf@honbori.ifi.uio.no...
> "Robert" <rac2901spam@spamsbcglobal . net > writes:
>> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
>
>>> When re-reading Ansel Adams' "The Negative", I came across by the
>>> following paragraph, which appears on pp. 42-43 in the 2002 editions,
>>> whivh I belive is a reprint of the 1981 edition:
>>>
>>> 'If pressed, the manufacturers of some exposure meters will
>>> acknowledge that they depart from standard calibration of their
>>> meters by incorporating a "K factor." This factor is supposed to
>>> give a higher percentage of acceptable images under average
>>> conditions than a meter calibrated exactly to an 18 percent
>>> reflectance. The practical effect of the K factor is that if we
>>> make a careful reading from a middle-gray surface and expose as
>>> indicated, the result will not be exactly a middle gray!'
>>>
>>> So far so good. This just indicates that the master also was aware
>>> of the same thing that Thom Hogan and others have observed, that
>>> "meters don't see 18% gray" ( * w w w .bythom . com /graycards.htm ).
>>>
>>> However, Adams goes om to say:
>>>
>>> With nearly all meters, this factor is equivalent to giving a
>>> one-third stop /increase/ in exposure.
>>>
>>> And it is not just a typo, on pp. 66-67 in the same book, Adams
>>> suggest that the photographer compensate for the K-factor upping the
>>> ASA dialed in the meter. By example, he said tha one should set ASA 80
>>> on the meter when shooting ASA 64 film. This, of course has the same
>>> effect as adjusting exposure by -1/3 EV.
>>>
>>> The reason I am puzzled by this, is because careful metering of
>>> a Kodak 18% grey card with a Sekonic L-778 spot meter confirms
>>> that the meter doesn't see 18% grey, but the offset result in
>>> about 1/2 stop /decrease/ in exposure, not an /increase/ as
>>> suggested by Adams. (I've checked this with other meters,
>>> and while readings differ by about +-1/6 EV, they all show a
>>> decrease with respect to a reading that would have placed
>>> the card at middle gray.
>>>
>>> And indeed, the instructions that came with my Kodak grey card said:
>>>
>>> For subjects of normal reflectance increase the indicated exposure
>>> by 1/2 stop.
>>>
>>> Kodak's instructions fits my observations exactly
>>> (if "normal reflectance" = "18% grey").
>
>> if you meter a gray card and it shows that it is 1/3 below 18%, when
>> it should be 18% then to bring it up to 18% gray you need to
>> increase it.
>
> So you agree that the information in "The Negative" is wrong on
> this particular point?
> --
No it is correct.
lets say you have a measuring cup that should hold 1 cup of water but you
test it and it only comes up 2/3 cup to compensate for the difference you
add an extra 1/3 cup so it will have a full cup. to off site the lower meter
reading you have to add the difference to equal the right amount.
Robert
Re: Puzzled by Adams, K factor and middle grey
"Robert" <rac2901spam@spamsbcglobal . net > wrote in message
news:54xSh.13189$JZ3.6503@newssvr13.news.prodigy . net ...
>
> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
> news:q5ejmt4d01.fsf@honbori.ifi.uio.no...
>> "Robert" <rac2901spam@spamsbcglobal . net > writes:
>>> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
>>
>>>> When re-reading Ansel Adams' "The Negative", I came across by the
>>>> following paragraph, which appears on pp. 42-43 in the 2002 editions,
>>>> whivh I belive is a reprint of the 1981 edition:
>>>>
>>>> 'If pressed, the manufacturers of some exposure meters will
>>>> acknowledge that they depart from standard calibration of their
>>>> meters by incorporating a "K factor." This factor is supposed to
>>>> give a higher percentage of acceptable images under average
>>>> conditions than a meter calibrated exactly to an 18 percent
>>>> reflectance. The practical effect of the K factor is that if we
>>>> make a careful reading from a middle-gray surface and expose as
>>>> indicated, the result will not be exactly a middle gray!'
>>>>
>>>> So far so good. This just indicates that the master also was aware
>>>> of the same thing that Thom Hogan and others have observed, that
>>>> "meters don't see 18% gray" ( * w w w .bythom . com /graycards.htm ).
>>>>
>>>> However, Adams goes om to say:
>>>>
>>>> With nearly all meters, this factor is equivalent to giving a
>>>> one-third stop /increase/ in exposure.
>>>>
>>>> And it is not just a typo, on pp. 66-67 in the same book, Adams
>>>> suggest that the photographer compensate for the K-factor upping the
>>>> ASA dialed in the meter. By example, he said tha one should set ASA 80
>>>> on the meter when shooting ASA 64 film. This, of course has the same
>>>> effect as adjusting exposure by -1/3 EV.
>>>>
>>>> The reason I am puzzled by this, is because careful metering of
>>>> a Kodak 18% grey card with a Sekonic L-778 spot meter confirms
>>>> that the meter doesn't see 18% grey, but the offset result in
>>>> about 1/2 stop /decrease/ in exposure, not an /increase/ as
>>>> suggested by Adams. (I've checked this with other meters,
>>>> and while readings differ by about +-1/6 EV, they all show a
>>>> decrease with respect to a reading that would have placed
>>>> the card at middle gray.
>>>>
>>>> And indeed, the instructions that came with my Kodak grey card said:
>>>>
>>>> For subjects of normal reflectance increase the indicated exposure
>>>> by 1/2 stop.
>>>>
>>>> Kodak's instructions fits my observations exactly
>>>> (if "normal reflectance" = "18% grey").
>>
>>> if you meter a gray card and it shows that it is 1/3 below 18%, when
>>> it should be 18% then to bring it up to 18% gray you need to
>>> increase it.
>>
>> So you agree that the information in "The Negative" is wrong on
>> this particular point?
>> --
>
> No it is correct.
>
> lets say you have a measuring cup that should hold 1 cup of water but you
> test it and it only comes up 2/3 cup to compensate for the difference you
> add an extra 1/3 cup so it will have a full cup. to off site the lower
> meter reading you have to add the difference to equal the right amount.
>
>
> Robert
>
>
Yes, but Adams book indicates that the K factor is an increase, not a
decrease, "this factor is equivalent to giving a one-third stop /increase/
in exposure," thus one would expect all meters to be 1/3 stop over 18%, not
under.
--
w w w .mattclara . com
"Robert" <rac2901spam@spamsbcglobal . net > wrote in message
news:54xSh.13189$JZ3.6503@newssvr13.news.prodigy . net ...
>
> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
> news:q5ejmt4d01.fsf@honbori.ifi.uio.no...
>> "Robert" <rac2901spam@spamsbcglobal . net > writes:
>>> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
>>
>>>> When re-reading Ansel Adams' "The Negative", I came across by the
>>>> following paragraph, which appears on pp. 42-43 in the 2002 editions,
>>>> whivh I belive is a reprint of the 1981 edition:
>>>>
>>>> 'If pressed, the manufacturers of some exposure meters will
>>>> acknowledge that they depart from standard calibration of their
>>>> meters by incorporating a "K factor." This factor is supposed to
>>>> give a higher percentage of acceptable images under average
>>>> conditions than a meter calibrated exactly to an 18 percent
>>>> reflectance. The practical effect of the K factor is that if we
>>>> make a careful reading from a middle-gray surface and expose as
>>>> indicated, the result will not be exactly a middle gray!'
>>>>
>>>> So far so good. This just indicates that the master also was aware
>>>> of the same thing that Thom Hogan and others have observed, that
>>>> "meters don't see 18% gray" ( * w w w .bythom . com /graycards.htm ).
>>>>
>>>> However, Adams goes om to say:
>>>>
>>>> With nearly all meters, this factor is equivalent to giving a
>>>> one-third stop /increase/ in exposure.
>>>>
>>>> And it is not just a typo, on pp. 66-67 in the same book, Adams
>>>> suggest that the photographer compensate for the K-factor upping the
>>>> ASA dialed in the meter. By example, he said tha one should set ASA 80
>>>> on the meter when shooting ASA 64 film. This, of course has the same
>>>> effect as adjusting exposure by -1/3 EV.
>>>>
>>>> The reason I am puzzled by this, is because careful metering of
>>>> a Kodak 18% grey card with a Sekonic L-778 spot meter confirms
>>>> that the meter doesn't see 18% grey, but the offset result in
>>>> about 1/2 stop /decrease/ in exposure, not an /increase/ as
>>>> suggested by Adams. (I've checked this with other meters,
>>>> and while readings differ by about +-1/6 EV, they all show a
>>>> decrease with respect to a reading that would have placed
>>>> the card at middle gray.
>>>>
>>>> And indeed, the instructions that came with my Kodak grey card said:
>>>>
>>>> For subjects of normal reflectance increase the indicated exposure
>>>> by 1/2 stop.
>>>>
>>>> Kodak's instructions fits my observations exactly
>>>> (if "normal reflectance" = "18% grey").
>>
>>> if you meter a gray card and it shows that it is 1/3 below 18%, when
>>> it should be 18% then to bring it up to 18% gray you need to
>>> increase it.
>>
>> So you agree that the information in "The Negative" is wrong on
>> this particular point?
>> --
>
> No it is correct.
>
> lets say you have a measuring cup that should hold 1 cup of water but you
> test it and it only comes up 2/3 cup to compensate for the difference you
> add an extra 1/3 cup so it will have a full cup. to off site the lower
> meter reading you have to add the difference to equal the right amount.
>
>
> Robert
>
>
Yes, but Adams book indicates that the K factor is an increase, not a
decrease, "this factor is equivalent to giving a one-third stop /increase/
in exposure," thus one would expect all meters to be 1/3 stop over 18%, not
under.
--
w w w .mattclara . com
Re: Puzzled by Adams, K factor and middle grey
"Matt Clara" <hey.wood.y@buzz.off> wrote in message
news:pu2dnXS-XaO_KofbnZ2dnUVZ_uejnZ2d@comcast . com ...
> "Robert" <rac2901spam@spamsbcglobal . net > wrote in message
> news:54xSh.13189$JZ3.6503@newssvr13.news.prodigy . net ...
>>
>> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
>> news:q5ejmt4d01.fsf@honbori.ifi.uio.no...
>>> "Robert" <rac2901spam@spamsbcglobal . net > writes:
>>>> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
>>>
>>>>> When re-reading Ansel Adams' "The Negative", I came across by the
>>>>> following paragraph, which appears on pp. 42-43 in the 2002 editions,
>>>>> whivh I belive is a reprint of the 1981 edition:
>>>>>
>>>>> 'If pressed, the manufacturers of some exposure meters will
>>>>> acknowledge that they depart from standard calibration of their
>>>>> meters by incorporating a "K factor." This factor is supposed to
>>>>> give a higher percentage of acceptable images under average
>>>>> conditions than a meter calibrated exactly to an 18 percent
>>>>> reflectance. The practical effect of the K factor is that if we
>>>>> make a careful reading from a middle-gray surface and expose as
>>>>> indicated, the result will not be exactly a middle gray!'
>>>>>
>>>>> So far so good. This just indicates that the master also was aware
>>>>> of the same thing that Thom Hogan and others have observed, that
>>>>> "meters don't see 18% gray" ( * w w w .bythom . com /graycards.htm ).
>>>>>
>>>>> However, Adams goes om to say:
>>>>>
>>>>> With nearly all meters, this factor is equivalent to giving a
>>>>> one-third stop /increase/ in exposure.
>>>>>
>>>>> And it is not just a typo, on pp. 66-67 in the same book, Adams
>>>>> suggest that the photographer compensate for the K-factor upping the
>>>>> ASA dialed in the meter. By example, he said tha one should set ASA 80
>>>>> on the meter when shooting ASA 64 film. This, of course has the same
>>>>> effect as adjusting exposure by -1/3 EV.
>>>>>
>>>>> The reason I am puzzled by this, is because careful metering of
>>>>> a Kodak 18% grey card with a Sekonic L-778 spot meter confirms
>>>>> that the meter doesn't see 18% grey, but the offset result in
>>>>> about 1/2 stop /decrease/ in exposure, not an /increase/ as
>>>>> suggested by Adams. (I've checked this with other meters,
>>>>> and while readings differ by about +-1/6 EV, they all show a
>>>>> decrease with respect to a reading that would have placed
>>>>> the card at middle gray.
>>>>>
>>>>> And indeed, the instructions that came with my Kodak grey card said:
>>>>>
>>>>> For subjects of normal reflectance increase the indicated exposure
>>>>> by 1/2 stop.
>>>>>
>>>>> Kodak's instructions fits my observations exactly
>>>>> (if "normal reflectance" = "18% grey").
>>>
>>>> if you meter a gray card and it shows that it is 1/3 below 18%, when
>>>> it should be 18% then to bring it up to 18% gray you need to
>>>> increase it.
>>>
>>> So you agree that the information in "The Negative" is wrong on
>>> this particular point?
>>> --
>>
>> No it is correct.
>>
>> lets say you have a measuring cup that should hold 1 cup of water but you
>> test it and it only comes up 2/3 cup to compensate for the difference you
>> add an extra 1/3 cup so it will have a full cup. to off site the lower
>> meter reading you have to add the difference to equal the right amount.
>>
>>
>> Robert
>>
>>
>
> Yes, but Adams book indicates that the K factor is an increase, not a
> decrease, "this factor is equivalent to giving a one-third stop /increase/
> in exposure," thus one would expect all meters to be 1/3 stop over 18%,
> not under.
>
> --
> w w w .mattclara . com
>
The meter is giving you a 1/3 underexposure to compensate the exposure you
add 1/3 for proper exposure.
no if your meter is 1/3 stop over then you add 1/3 you are 2/3 over. were
it is giving a reading that is 1/3 short you add 1/3 you compensate for the
low reading.
as my example;
18% grey = 1 cup of water
meter only shows that it is 2/3 cup of water because Its 1/3 under exposure
.
If you adjust exposure to 1 1/3 cup of water the meter will see 1 cup (=18%
gray) because of the k factor the meter reading is 1/3 less.
Robert
"Matt Clara" <hey.wood.y@buzz.off> wrote in message
news:pu2dnXS-XaO_KofbnZ2dnUVZ_uejnZ2d@comcast . com ...
> "Robert" <rac2901spam@spamsbcglobal . net > wrote in message
> news:54xSh.13189$JZ3.6503@newssvr13.news.prodigy . net ...
>>
>> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
>> news:q5ejmt4d01.fsf@honbori.ifi.uio.no...
>>> "Robert" <rac2901spam@spamsbcglobal . net > writes:
>>>> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
>>>
>>>>> When re-reading Ansel Adams' "The Negative", I came across by the
>>>>> following paragraph, which appears on pp. 42-43 in the 2002 editions,
>>>>> whivh I belive is a reprint of the 1981 edition:
>>>>>
>>>>> 'If pressed, the manufacturers of some exposure meters will
>>>>> acknowledge that they depart from standard calibration of their
>>>>> meters by incorporating a "K factor." This factor is supposed to
>>>>> give a higher percentage of acceptable images under average
>>>>> conditions than a meter calibrated exactly to an 18 percent
>>>>> reflectance. The practical effect of the K factor is that if we
>>>>> make a careful reading from a middle-gray surface and expose as
>>>>> indicated, the result will not be exactly a middle gray!'
>>>>>
>>>>> So far so good. This just indicates that the master also was aware
>>>>> of the same thing that Thom Hogan and others have observed, that
>>>>> "meters don't see 18% gray" ( * w w w .bythom . com /graycards.htm ).
>>>>>
>>>>> However, Adams goes om to say:
>>>>>
>>>>> With nearly all meters, this factor is equivalent to giving a
>>>>> one-third stop /increase/ in exposure.
>>>>>
>>>>> And it is not just a typo, on pp. 66-67 in the same book, Adams
>>>>> suggest that the photographer compensate for the K-factor upping the
>>>>> ASA dialed in the meter. By example, he said tha one should set ASA 80
>>>>> on the meter when shooting ASA 64 film. This, of course has the same
>>>>> effect as adjusting exposure by -1/3 EV.
>>>>>
>>>>> The reason I am puzzled by this, is because careful metering of
>>>>> a Kodak 18% grey card with a Sekonic L-778 spot meter confirms
>>>>> that the meter doesn't see 18% grey, but the offset result in
>>>>> about 1/2 stop /decrease/ in exposure, not an /increase/ as
>>>>> suggested by Adams. (I've checked this with other meters,
>>>>> and while readings differ by about +-1/6 EV, they all show a
>>>>> decrease with respect to a reading that would have placed
>>>>> the card at middle gray.
>>>>>
>>>>> And indeed, the instructions that came with my Kodak grey card said:
>>>>>
>>>>> For subjects of normal reflectance increase the indicated exposure
>>>>> by 1/2 stop.
>>>>>
>>>>> Kodak's instructions fits my observations exactly
>>>>> (if "normal reflectance" = "18% grey").
>>>
>>>> if you meter a gray card and it shows that it is 1/3 below 18%, when
>>>> it should be 18% then to bring it up to 18% gray you need to
>>>> increase it.
>>>
>>> So you agree that the information in "The Negative" is wrong on
>>> this particular point?
>>> --
>>
>> No it is correct.
>>
>> lets say you have a measuring cup that should hold 1 cup of water but you
>> test it and it only comes up 2/3 cup to compensate for the difference you
>> add an extra 1/3 cup so it will have a full cup. to off site the lower
>> meter reading you have to add the difference to equal the right amount.
>>
>>
>> Robert
>>
>>
>
> Yes, but Adams book indicates that the K factor is an increase, not a
> decrease, "this factor is equivalent to giving a one-third stop /increase/
> in exposure," thus one would expect all meters to be 1/3 stop over 18%,
> not under.
>
> --
> w w w .mattclara . com
>
The meter is giving you a 1/3 underexposure to compensate the exposure you
add 1/3 for proper exposure.
no if your meter is 1/3 stop over then you add 1/3 you are 2/3 over. were
it is giving a reading that is 1/3 short you add 1/3 you compensate for the
low reading.
as my example;
18% grey = 1 cup of water
meter only shows that it is 2/3 cup of water because Its 1/3 under exposure
.
If you adjust exposure to 1 1/3 cup of water the meter will see 1 cup (=18%
gray) because of the k factor the meter reading is 1/3 less.
Robert
Re: Puzzled by Adams, K factor and middle grey
Gisle Hannemyr spake thus:
[snip]
> So ...
> To me it looks like Adams somehow managed to get the bit about
> teh K Factor backwards.
>
> The reason I am posting this here is basically to get some
> second opinions on this. Did the great one bungle this particular
> detail, or is there something that I've misunderstood?
If it's a mistake, it could have been Adams, or it could have been his
editor.
--
I hope that in a few years it [Wikipedia] will be so bloated that it
will simply disintegrate, because I can't stand the thought that this
thing might someday actually be used as a serious reference source.
Because in its current form, it's not to be taken seriously at all.
- Horst Prillinger (see
* homepage.univie.ac.at/horst.prillinger/blog/archives/2004/06/000623.html)
Gisle Hannemyr spake thus:
[snip]
> So ...
> To me it looks like Adams somehow managed to get the bit about
> teh K Factor backwards.
>
> The reason I am posting this here is basically to get some
> second opinions on this. Did the great one bungle this particular
> detail, or is there something that I've misunderstood?
If it's a mistake, it could have been Adams, or it could have been his
editor.
--
I hope that in a few years it [Wikipedia] will be so bloated that it
will simply disintegrate, because I can't stand the thought that this
thing might someday actually be used as a serious reference source.
Because in its current form, it's not to be taken seriously at all.
- Horst Prillinger (see
* homepage.univie.ac.at/horst.prillinger/blog/archives/2004/06/000623.html)
Re: Puzzled by Adams, K factor and middle grey
"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:461a77cb$0$18169$822641b3@news.adtechcomputers . com ...
> Gisle Hannemyr spake thus:
>
> [snip]
>
> I hope that in a few years it [Wikipedia] will be so bloated that it
> will simply disintegrate, because I can't stand the thought that this
> thing might someday actually be used as a serious reference source.
> Because in its current form, it's not to be taken seriously at all.
>
> - Horst Prillinger (see
> * homepage.univie.ac.at/horst.prillinger/blog/archives/2004/06/000623.html)
David, I'm sorry I can't leave it alone, but then, neither can you. Please,
state the specific time and place wikipedia let you down, when you were left
by the side of the road, fubared, if you will, by wikipedia. There is no
such instance, of course. Please compare wikipedia to any other free source
of info on the web, and you'll see it far exceeds everything out there.
Your continued, adolescent umbrage against wikipedia flies in the face of
the perfectly acceptable--if not perfect--information we've received there.
Further, I think you embarrass yourself with your continued quotes from
people we've never heard of, or in the case of Harlan Ellison, a person
known for his quick temper and iracibility.
Personally, I've used Wikipedia recently for information on The Band. If
that information is less than 100% correct, who gives two shits? It's more
than good enough. I've also used it for info on MI rivers. Before
wikipedia, I would have had to search several half-assed websites for less
than a quarter of the info I found there on that subject. Is it perfect?
Probably not. Could I care less? Hell no. It's already proven more
accurate than the book I bought on the subject.
Will wikipedia be surplanted by something more accurate in time? Probably,
but this is where we are now, and in terms of concentrated info on the
internet, wikipedia kicks ass.
--
w w w .mattclara . com
ps. who the fuck is Horst Prillinger? I have two degrees in Philosophy and
English, and I've never heard of him!?! Why should we accept what he has to
say on the web, but not Wikipedia? Your thinking is fundamentally flawed on
this issue. Period.
"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:461a77cb$0$18169$822641b3@news.adtechcomputers . com ...
> Gisle Hannemyr spake thus:
>
> [snip]
>
> I hope that in a few years it [Wikipedia] will be so bloated that it
> will simply disintegrate, because I can't stand the thought that this
> thing might someday actually be used as a serious reference source.
> Because in its current form, it's not to be taken seriously at all.
>
> - Horst Prillinger (see
> * homepage.univie.ac.at/horst.prillinger/blog/archives/2004/06/000623.html)
David, I'm sorry I can't leave it alone, but then, neither can you. Please,
state the specific time and place wikipedia let you down, when you were left
by the side of the road, fubared, if you will, by wikipedia. There is no
such instance, of course. Please compare wikipedia to any other free source
of info on the web, and you'll see it far exceeds everything out there.
Your continued, adolescent umbrage against wikipedia flies in the face of
the perfectly acceptable--if not perfect--information we've received there.
Further, I think you embarrass yourself with your continued quotes from
people we've never heard of, or in the case of Harlan Ellison, a person
known for his quick temper and iracibility.
Personally, I've used Wikipedia recently for information on The Band. If
that information is less than 100% correct, who gives two shits? It's more
than good enough. I've also used it for info on MI rivers. Before
wikipedia, I would have had to search several half-assed websites for less
than a quarter of the info I found there on that subject. Is it perfect?
Probably not. Could I care less? Hell no. It's already proven more
accurate than the book I bought on the subject.
Will wikipedia be surplanted by something more accurate in time? Probably,
but this is where we are now, and in terms of concentrated info on the
internet, wikipedia kicks ass.
--
w w w .mattclara . com
ps. who the fuck is Horst Prillinger? I have two degrees in Philosophy and
English, and I've never heard of him!?! Why should we accept what he has to
say on the web, but not Wikipedia? Your thinking is fundamentally flawed on
this issue. Period.
Re: Puzzled by Adams, K factor and middle grey
Matt Clara" <hey.wood.y@buzz.off> wrote in message
news:4MmdnQX8pIpCd4fbnZ2dnUVZ_tadnZ2d@comcast . com ...
> "David Nebenzahl" <nobody@but.us.chickens> wrote in message
> news:461a77cb$0$18169$822641b3@news.adtechcomputers . com ...
>> Gisle Hannemyr spake thus:
>>
>> [snip]
>>
>> I hope that in a few years it [Wikipedia] will be so bloated that it
>> will simply disintegrate, because I can't stand the thought that this
>> thing might someday actually be used as a serious reference source.
>> Because in its current form, it's not to be taken seriously at all.
>>
>> - Horst Prillinger (see
>> * homepage.univie.ac.at/horst.prillinger/blog/archives/2004/06/000623.html)
>
> David, I'm sorry I can't leave it alone, but then, neither can you.
> Please, state the specific time and place wikipedia let you down, when you
> were left by the side of the road, fubared, if you will, by wikipedia.
> There is no such instance, of course. Please compare wikipedia to any
> other free source of info on the web, and you'll see it far exceeds
> everything out there. Your continued, adolescent umbrage against wikipedia
> flies in the face of the perfectly acceptable--if not perfect--information
> we've received there. Further, I think you embarrass yourself with your
> continued quotes from people we've never heard of, or in the case of
> Harlan Ellison, a person known for his quick temper and iracibility.
>
> Personally, I've used Wikipedia recently for information on The Band. If
> that information is less than 100% correct, who gives two shits? It's
> more than good enough. I've also used it for info on MI rivers. Before
> wikipedia, I would have had to search several half-assed websites for less
> than a quarter of the info I found there on that subject. Is it perfect?
> Probably not. Could I care less? Hell no. It's already proven more
> accurate than the book I bought on the subject.
>
> Will wikipedia be surplanted by something more accurate in time?
> Probably, but this is where we are now, and in terms of concentrated info
> on the internet, wikipedia kicks ass.
>
> --
> w w w .mattclara . com
> ps. who the fuck is Horst Prillinger? I have two degrees in Philosophy
> and English, and I've never heard of him!?! Why should we accept what he
> has to say on the web, but not Wikipedia? Your thinking is fundamentally
> flawed on this issue. Period.
>
You're like the kids I used to teach writing to. They'd rail against
anything their parents did, without real reason to...
Why not just quit quoting all these people we've never heard of and state
the case in your own word?
What, don't your have a case of your own?
--
w w w .mattclara . com
Matt Clara" <hey.wood.y@buzz.off> wrote in message
news:4MmdnQX8pIpCd4fbnZ2dnUVZ_tadnZ2d@comcast . com ...
> "David Nebenzahl" <nobody@but.us.chickens> wrote in message
> news:461a77cb$0$18169$822641b3@news.adtechcomputers . com ...
>> Gisle Hannemyr spake thus:
>>
>> [snip]
>>
>> I hope that in a few years it [Wikipedia] will be so bloated that it
>> will simply disintegrate, because I can't stand the thought that this
>> thing might someday actually be used as a serious reference source.
>> Because in its current form, it's not to be taken seriously at all.
>>
>> - Horst Prillinger (see
>> * homepage.univie.ac.at/horst.prillinger/blog/archives/2004/06/000623.html)
>
> David, I'm sorry I can't leave it alone, but then, neither can you.
> Please, state the specific time and place wikipedia let you down, when you
> were left by the side of the road, fubared, if you will, by wikipedia.
> There is no such instance, of course. Please compare wikipedia to any
> other free source of info on the web, and you'll see it far exceeds
> everything out there. Your continued, adolescent umbrage against wikipedia
> flies in the face of the perfectly acceptable--if not perfect--information
> we've received there. Further, I think you embarrass yourself with your
> continued quotes from people we've never heard of, or in the case of
> Harlan Ellison, a person known for his quick temper and iracibility.
>
> Personally, I've used Wikipedia recently for information on The Band. If
> that information is less than 100% correct, who gives two shits? It's
> more than good enough. I've also used it for info on MI rivers. Before
> wikipedia, I would have had to search several half-assed websites for less
> than a quarter of the info I found there on that subject. Is it perfect?
> Probably not. Could I care less? Hell no. It's already proven more
> accurate than the book I bought on the subject.
>
> Will wikipedia be surplanted by something more accurate in time?
> Probably, but this is where we are now, and in terms of concentrated info
> on the internet, wikipedia kicks ass.
>
> --
> w w w .mattclara . com
> ps. who the fuck is Horst Prillinger? I have two degrees in Philosophy
> and English, and I've never heard of him!?! Why should we accept what he
> has to say on the web, but not Wikipedia? Your thinking is fundamentally
> flawed on this issue. Period.
>
You're like the kids I used to teach writing to. They'd rail against
anything their parents did, without real reason to...
Why not just quit quoting all these people we've never heard of and state
the case in your own word?
What, don't your have a case of your own?
--
w w w .mattclara . com
Re: Puzzled by Adams, K factor and middle grey
Matt Clara wrote in message
<4MmdnQX8pIpCd4fbnZ2dnUVZ_tadnZ2d@comcast . com >...
>"David Nebenzahl" <nobody@but.us.chickens> wrote in message
>news:461a77cb$0$18169$822641b3@news.adtechcomputers . com ...
>> Gisle Hannemyr spake thus:
>>
>> [snip]
>>
>> I hope that in a few years it [Wikipedia] will be so bloated that it
>> will simply disintegrate, because I can't stand the thought that this
>> thing might someday actually be used as a serious reference source.
>> Because in its current form, it's not to be taken seriously at all.
>>
>> - Horst Prillinger (see
>>
* homepage.univie.ac.at/horst.prillinger/blog/archives/2004/06/000623.h
tml)
>
>David, I'm sorry I can't leave it alone, but then, neither can you.
Please,
>state the specific time and place wikipedia let you down, when you were
left
>by the side of the road, fubared, if you will, by wikipedia. There is no
>such instance, of course. Please compare wikipedia to any other free
source
>of info on the web, and you'll see it far exceeds everything out there.
>Your continued, adolescent umbrage against wikipedia flies in the face of
>the perfectly acceptable--if not perfect--information we've received there.
>Further, I think you embarrass yourself with your continued quotes from
>people we've never heard of, or in the case of Harlan Ellison, a person
>known for his quick temper and iracibility.
>
>Personally, I've used Wikipedia recently for information on The Band. If
>that information is less than 100% correct, who gives two shits? It's more
>than good enough. I've also used it for info on MI rivers. Before
>wikipedia, I would have had to search several half-assed websites for less
>than a quarter of the info I found there on that subject. Is it perfect?
>Probably not. Could I care less? Hell no. It's already proven more
>accurate than the book I bought on the subject.
>
>Will wikipedia be surplanted by something more accurate in time? Probably,
>but this is where we are now, and in terms of concentrated info on the
>internet, wikipedia kicks ass.
>
>--
>w w w .mattclara . com
>ps. who the fuck is Horst Prillinger? I have two degrees in Philosophy and
>English, and I've never heard of him!?! Why should we accept what he has to
>say on the web, but not Wikipedia? Your thinking is fundamentally flawed
on
>this issue. Period.
>
>
That's not a really fair challenge. I have checked wikipedia a couple times
where the information was so wildly wrong I couldn't even believe it.
But I didn't know that someone would ever challenge my memory of it so now I
don't remember what the subject was
Matt Clara wrote in message
<4MmdnQX8pIpCd4fbnZ2dnUVZ_tadnZ2d@comcast . com >...
>"David Nebenzahl" <nobody@but.us.chickens> wrote in message
>news:461a77cb$0$18169$822641b3@news.adtechcomputers . com ...
>> Gisle Hannemyr spake thus:
>>
>> [snip]
>>
>> I hope that in a few years it [Wikipedia] will be so bloated that it
>> will simply disintegrate, because I can't stand the thought that this
>> thing might someday actually be used as a serious reference source.
>> Because in its current form, it's not to be taken seriously at all.
>>
>> - Horst Prillinger (see
>>
* homepage.univie.ac.at/horst.prillinger/blog/archives/2004/06/000623.h
tml)
>
>David, I'm sorry I can't leave it alone, but then, neither can you.
Please,
>state the specific time and place wikipedia let you down, when you were
left
>by the side of the road, fubared, if you will, by wikipedia. There is no
>such instance, of course. Please compare wikipedia to any other free
source
>of info on the web, and you'll see it far exceeds everything out there.
>Your continued, adolescent umbrage against wikipedia flies in the face of
>the perfectly acceptable--if not perfect--information we've received there.
>Further, I think you embarrass yourself with your continued quotes from
>people we've never heard of, or in the case of Harlan Ellison, a person
>known for his quick temper and iracibility.
>
>Personally, I've used Wikipedia recently for information on The Band. If
>that information is less than 100% correct, who gives two shits? It's more
>than good enough. I've also used it for info on MI rivers. Before
>wikipedia, I would have had to search several half-assed websites for less
>than a quarter of the info I found there on that subject. Is it perfect?
>Probably not. Could I care less? Hell no. It's already proven more
>accurate than the book I bought on the subject.
>
>Will wikipedia be surplanted by something more accurate in time? Probably,
>but this is where we are now, and in terms of concentrated info on the
>internet, wikipedia kicks ass.
>
>--
>w w w .mattclara . com
>ps. who the fuck is Horst Prillinger? I have two degrees in Philosophy and
>English, and I've never heard of him!?! Why should we accept what he has to
>say on the web, but not Wikipedia? Your thinking is fundamentally flawed
on
>this issue. Period.
>
>
That's not a really fair challenge. I have checked wikipedia a couple times
where the information was so wildly wrong I couldn't even believe it.
But I didn't know that someone would ever challenge my memory of it so now I
don't remember what the subject was
Re: Puzzled by Adams, K factor and middle grey
"Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote
> When re-reading Ansel Adams' "The Negative", I came across by the
> following paragraph, which appears on pp. 42-43 in the 2002 editions,
> whivh I belive is a reprint of the 1981 edition:
>
> 'If pressed, the manufacturers of some exposure meters will
> acknowledge that they depart from standard calibration of their
> meters by incorporating a "K factor."
Here opens a huge can of worms that is almost impossible to
sort through. Uncontrolled variables include: the spectral
response of the meter, the spectral response of the film,
the spectrum of the light source and the remission spectrum
of the grey card.
Different meters, different grey cards, different light sources,
different films, different methods and everyone gets different
results.
Don't take it too seriously. The K-Factor is the same as
establishing a 'personal speed rating' for a film.
I think the 1/3 stop thing and the "K factor" got it's start
with Kodachrome film. Kodak decided average slides for the
average photographer had a better percentage of acceptable
exposure if the meter was set to 64 (for K64). People
with accurate meters and good technique found out that
setting the meter at 80 gave more saturated colors at
the risk of having no underexposure latitude. This
is still true and woe betide he who meters sloppily... To
confound the Kodachrome situation averaging meters work best,
fancy spot metering usually results in disaster. The K factor
is what it takes to make Kodachrome come out right.
The goal with slides is to get a slide that _looks_ good: no
one gives a whit about response curves and densities because
there is no variation possible except for the exposure. When
camera makers decide where to set the meter they load up the
prototypes with Kodachrome and see what setting gives the best
results - instrumentation be damned. Kodachrome is the one
situation where the exposure _has_ to be correct. For B&W
or C-41 just overexpose a stop or two and don't worry about
it: hence most P&S cameras will overexpose slides by a few stops
and produce unusable results - the Yashica T4 was a notable
exception [there were/are others].
With B&W there are many things that can be varied and vary
them man must. Something about the disorder of the Universe
being ever increasing. It is possible to move the K factor
around at will as long as one doesn't underexpose and in the
final analysis it doesn't matter a whole lot what K value is
used.
As to what his books say, Ansel Adams is as likely to get
confused as the next man. I don't know of a single
serious photography book that doesn't put it's foot in
it somewhere or other.
--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
* w w w .darkroomautomation . com /index.htm
n o lindan at ix dot netcom dot com
"Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote
> When re-reading Ansel Adams' "The Negative", I came across by the
> following paragraph, which appears on pp. 42-43 in the 2002 editions,
> whivh I belive is a reprint of the 1981 edition:
>
> 'If pressed, the manufacturers of some exposure meters will
> acknowledge that they depart from standard calibration of their
> meters by incorporating a "K factor."
Here opens a huge can of worms that is almost impossible to
sort through. Uncontrolled variables include: the spectral
response of the meter, the spectral response of the film,
the spectrum of the light source and the remission spectrum
of the grey card.
Different meters, different grey cards, different light sources,
different films, different methods and everyone gets different
results.
Don't take it too seriously. The K-Factor is the same as
establishing a 'personal speed rating' for a film.
I think the 1/3 stop thing and the "K factor" got it's start
with Kodachrome film. Kodak decided average slides for the
average photographer had a better percentage of acceptable
exposure if the meter was set to 64 (for K64). People
with accurate meters and good technique found out that
setting the meter at 80 gave more saturated colors at
the risk of having no underexposure latitude. This
is still true and woe betide he who meters sloppily... To
confound the Kodachrome situation averaging meters work best,
fancy spot metering usually results in disaster. The K factor
is what it takes to make Kodachrome come out right.
The goal with slides is to get a slide that _looks_ good: no
one gives a whit about response curves and densities because
there is no variation possible except for the exposure. When
camera makers decide where to set the meter they load up the
prototypes with Kodachrome and see what setting gives the best
results - instrumentation be damned. Kodachrome is the one
situation where the exposure _has_ to be correct. For B&W
or C-41 just overexpose a stop or two and don't worry about
it: hence most P&S cameras will overexpose slides by a few stops
and produce unusable results - the Yashica T4 was a notable
exception [there were/are others].
With B&W there are many things that can be varied and vary
them man must. Something about the disorder of the Universe
being ever increasing. It is possible to move the K factor
around at will as long as one doesn't underexpose and in the
final analysis it doesn't matter a whole lot what K value is
used.
As to what his books say, Ansel Adams is as likely to get
confused as the next man. I don't know of a single
serious photography book that doesn't put it's foot in
it somewhere or other.
--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
* w w w .darkroomautomation . com /index.htm
n o lindan at ix dot netcom dot com
Re: Puzzled by Adams, K factor and middle grey
Nicholas O. Lindan wrote in message
<2uySh.135952$_73.86219@newsread2.news.pas.earthlink . net >...
>"Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote
>> When re-reading Ansel Adams' "The Negative", I came across by the
>> following paragraph, which appears on pp. 42-43 in the 2002 editions,
>> whivh I belive is a reprint of the 1981 edition:
>>
>> 'If pressed, the manufacturers of some exposure meters will
>> acknowledge that they depart from standard calibration of their
>> meters by incorporating a "K factor."
>
>Here opens a huge can of worms that is almost impossible to
>sort through.
that's so funny. as a metaphor.
why in the world would someone want to sort through worms.
>Uncontrolled variables include: the spectral
>response of the meter, the spectral response of the film,
>the spectrum of the light source and the remission spectrum
>of the grey card.
>
>Different meters, different grey cards, different light sources,
>different films, different methods and everyone gets different
>results.
>
>Don't take it too seriously. The K-Factor is the same as
>establishing a 'personal speed rating' for a film.
>
>I think the 1/3 stop thing and the "K factor" got it's start
>with Kodachrome film. Kodak decided average slides for the
>average photographer had a better percentage of acceptable
>exposure if the meter was set to 64 (for K64). People
>with accurate meters and good technique found out that
>setting the meter at 80 gave more saturated colors at
>the risk of having no underexposure latitude. This
>is still true and woe betide he who meters sloppily... To
>confound the Kodachrome situation averaging meters work best,
>fancy spot metering usually results in disaster. The K factor
>is what it takes to make Kodachrome come out right.
>
>The goal with slides is to get a slide that _looks_ good: no
>one gives a whit about response curves and densities because
>there is no variation possible except for the exposure. When
>camera makers decide where to set the meter they load up the
>prototypes with Kodachrome and see what setting gives the best
>results - instrumentation be damned. Kodachrome is the one
>situation where the exposure _has_ to be correct. For B&W
>or C-41 just overexpose a stop or two and don't worry about
>it: hence most P&S cameras will overexpose slides by a few stops
>and produce unusable results - the Yashica T4 was a notable
>exception [there were/are others].
>
>With B&W there are many things that can be varied and vary
>them man must. Something about the disorder of the Universe
>being ever increasing. It is possible to move the K factor
>around at will as long as one doesn't underexpose and in the
>final analysis it doesn't matter a whole lot what K value is
>used.
>
>As to what his books say, Ansel Adams is as likely to get
>confused as the next man. I don't know of a single
>serious photography book that doesn't put it's foot in
>it somewhere or other.
>
>--
>Nicholas O. Lindan, Cleveland, Ohio
>Darkroom Automation: F-Stop Timers, Enlarging Meters
> * w w w .darkroomautomation . com /index.htm
>n o lindan at ix dot netcom dot com
>
>
Nicholas O. Lindan wrote in message
<2uySh.135952$_73.86219@newsread2.news.pas.earthlink . net >...
>"Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote
>> When re-reading Ansel Adams' "The Negative", I came across by the
>> following paragraph, which appears on pp. 42-43 in the 2002 editions,
>> whivh I belive is a reprint of the 1981 edition:
>>
>> 'If pressed, the manufacturers of some exposure meters will
>> acknowledge that they depart from standard calibration of their
>> meters by incorporating a "K factor."
>
>Here opens a huge can of worms that is almost impossible to
>sort through.
that's so funny. as a metaphor.
why in the world would someone want to sort through worms.
>Uncontrolled variables include: the spectral
>response of the meter, the spectral response of the film,
>the spectrum of the light source and the remission spectrum
>of the grey card.
>
>Different meters, different grey cards, different light sources,
>different films, different methods and everyone gets different
>results.
>
>Don't take it too seriously. The K-Factor is the same as
>establishing a 'personal speed rating' for a film.
>
>I think the 1/3 stop thing and the "K factor" got it's start
>with Kodachrome film. Kodak decided average slides for the
>average photographer had a better percentage of acceptable
>exposure if the meter was set to 64 (for K64). People
>with accurate meters and good technique found out that
>setting the meter at 80 gave more saturated colors at
>the risk of having no underexposure latitude. This
>is still true and woe betide he who meters sloppily... To
>confound the Kodachrome situation averaging meters work best,
>fancy spot metering usually results in disaster. The K factor
>is what it takes to make Kodachrome come out right.
>
>The goal with slides is to get a slide that _looks_ good: no
>one gives a whit about response curves and densities because
>there is no variation possible except for the exposure. When
>camera makers decide where to set the meter they load up the
>prototypes with Kodachrome and see what setting gives the best
>results - instrumentation be damned. Kodachrome is the one
>situation where the exposure _has_ to be correct. For B&W
>or C-41 just overexpose a stop or two and don't worry about
>it: hence most P&S cameras will overexpose slides by a few stops
>and produce unusable results - the Yashica T4 was a notable
>exception [there were/are others].
>
>With B&W there are many things that can be varied and vary
>them man must. Something about the disorder of the Universe
>being ever increasing. It is possible to move the K factor
>around at will as long as one doesn't underexpose and in the
>final analysis it doesn't matter a whole lot what K value is
>used.
>
>As to what his books say, Ansel Adams is as likely to get
>confused as the next man. I don't know of a single
>serious photography book that doesn't put it's foot in
>it somewhere or other.
>
>--
>Nicholas O. Lindan, Cleveland, Ohio
>Darkroom Automation: F-Stop Timers, Enlarging Meters
> * w w w .darkroomautomation . com /index.htm
>n o lindan at ix dot netcom dot com
>
>
Re: Puzzled by Adams, K factor and middle grey
Obviously never gone fishing, you sort through the worms to
find one that looks attractive to the fish (grin).
darkroommike
marika wrote:
> Nicholas O. Lindan wrote in message
> <2uySh.135952$ 73.86219@newsread2.news.pas.earthlink . net >...
>> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote
>>> When re-reading Ansel Adams' "The Negative", I came across by the
>>> following paragraph, which appears on pp. 42-43 in the 2002 editions,
>>> whivh I belive is a reprint of the 1981 edition:
>>>
>>> 'If pressed, the manufacturers of some exposure meters will
>>> acknowledge that they depart from standard calibration of their
>>> meters by incorporating a "K factor."
>> Here opens a huge can of worms that is almost impossible to
>> sort through.
>
> that's so funny. as a metaphor.
>
> why in the world would someone want to sort through worms.
>
>> Uncontrolled variables include: the spectral
>> response of the meter, the spectral response of the film,
>> the spectrum of the light source and the remission spectrum
>> of the grey card.
>>
>> Different meters, different grey cards, different light sources,
>> different films, different methods and everyone gets different
>> results.
>>
>> Don't take it too seriously. The K-Factor is the same as
>> establishing a 'personal speed rating' for a film.
>>
>> I think the 1/3 stop thing and the "K factor" got it's start
>> with Kodachrome film. Kodak decided average slides for the
>> average photographer had a better percentage of acceptable
>> exposure if the meter was set to 64 (for K64). People
>> with accurate meters and good technique found out that
>> setting the meter at 80 gave more saturated colors at
>> the risk of having no underexposure latitude. This
>> is still true and woe betide he who meters sloppily... To
>> confound the Kodachrome situation averaging meters work best,
>> fancy spot metering usually results in disaster. The K factor
>> is what it takes to make Kodachrome come out right.
>>
>> The goal with slides is to get a slide that looks good: no
>> one gives a whit about response curves and densities because
>> there is no variation possible except for the exposure. When
>> camera makers decide where to set the meter they load up the
>> prototypes with Kodachrome and see what setting gives the best
>> results - instrumentation be damned. Kodachrome is the one
>> situation where the exposure has to be correct. For B&W
>> or C-41 just overexpose a stop or two and don't worry about
>> it: hence most P&S cameras will overexpose slides by a few stops
>> and produce unusable results - the Yashica T4 was a notable
>> exception [there were/are others].
>>
>> With B&W there are many things that can be varied and vary
>> them man must. Something about the disorder of the Universe
>> being ever increasing. It is possible to move the K factor
>> around at will as long as one doesn't underexpose and in the
>> final analysis it doesn't matter a whole lot what K value is
>> used.
>>
>> As to what his books say, Ansel Adams is as likely to get
>> confused as the next man. I don't know of a single
>> serious photography book that doesn't put it's foot in
>> it somewhere or other.
>>
>> --
>> Nicholas O. Lindan, Cleveland, Ohio
>> Darkroom Automation: F-Stop Timers, Enlarging Meters
>> * w w w .darkroomautomation . com /index.htm
>> n o lindan at ix dot netcom dot com
>>
>>
>
>
Obviously never gone fishing, you sort through the worms to
find one that looks attractive to the fish (grin).
darkroommike
marika wrote:
> Nicholas O. Lindan wrote in message
> <2uySh.135952$ 73.86219@newsread2.news.pas.earthlink . net >...
>> "Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote
>>> When re-reading Ansel Adams' "The Negative", I came across by the
>>> following paragraph, which appears on pp. 42-43 in the 2002 editions,
>>> whivh I belive is a reprint of the 1981 edition:
>>>
>>> 'If pressed, the manufacturers of some exposure meters will
>>> acknowledge that they depart from standard calibration of their
>>> meters by incorporating a "K factor."
>> Here opens a huge can of worms that is almost impossible to
>> sort through.
>
> that's so funny. as a metaphor.
>
> why in the world would someone want to sort through worms.
>
>> Uncontrolled variables include: the spectral
>> response of the meter, the spectral response of the film,
>> the spectrum of the light source and the remission spectrum
>> of the grey card.
>>
>> Different meters, different grey cards, different light sources,
>> different films, different methods and everyone gets different
>> results.
>>
>> Don't take it too seriously. The K-Factor is the same as
>> establishing a 'personal speed rating' for a film.
>>
>> I think the 1/3 stop thing and the "K factor" got it's start
>> with Kodachrome film. Kodak decided average slides for the
>> average photographer had a better percentage of acceptable
>> exposure if the meter was set to 64 (for K64). People
>> with accurate meters and good technique found out that
>> setting the meter at 80 gave more saturated colors at
>> the risk of having no underexposure latitude. This
>> is still true and woe betide he who meters sloppily... To
>> confound the Kodachrome situation averaging meters work best,
>> fancy spot metering usually results in disaster. The K factor
>> is what it takes to make Kodachrome come out right.
>>
>> The goal with slides is to get a slide that looks good: no
>> one gives a whit about response curves and densities because
>> there is no variation possible except for the exposure. When
>> camera makers decide where to set the meter they load up the
>> prototypes with Kodachrome and see what setting gives the best
>> results - instrumentation be damned. Kodachrome is the one
>> situation where the exposure has to be correct. For B&W
>> or C-41 just overexpose a stop or two and don't worry about
>> it: hence most P&S cameras will overexpose slides by a few stops
>> and produce unusable results - the Yashica T4 was a notable
>> exception [there were/are others].
>>
>> With B&W there are many things that can be varied and vary
>> them man must. Something about the disorder of the Universe
>> being ever increasing. It is possible to move the K factor
>> around at will as long as one doesn't underexpose and in the
>> final analysis it doesn't matter a whole lot what K value is
>> used.
>>
>> As to what his books say, Ansel Adams is as likely to get
>> confused as the next man. I don't know of a single
>> serious photography book that doesn't put it's foot in
>> it somewhere or other.
>>
>> --
>> Nicholas O. Lindan, Cleveland, Ohio
>> Darkroom Automation: F-Stop Timers, Enlarging Meters
>> * w w w .darkroomautomation . com /index.htm
>> n o lindan at ix dot netcom dot com
>>
>>
>
>
Re: Puzzled by Adams, K factor and middle grey
marika wrote:
> Nicholas O. Lindan wrote in message
>> Here opens a huge can of worms that is almost impossible to
>> sort through.
>
> that's so funny. as a metaphor.
>
> why in the world would someone want to sort through worms.
If the fish ain't bitin' ...
marika wrote:
> Nicholas O. Lindan wrote in message
>> Here opens a huge can of worms that is almost impossible to
>> sort through.
>
> that's so funny. as a metaphor.
>
> why in the world would someone want to sort through worms.
If the fish ain't bitin' ...
Re: Puzzled by Adams, K factor and middle grey
"Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
news:q5tzvp7f7v.fsf@kaksi.ifi.uio.no...
> When re-reading Ansel Adams' "The Negative", I came across
> by the
> following paragraph, which appears on pp. 42-43 in the
> 2002 editions,
> whivh I belive is a reprint of the 1981 edition:
>
> 'If pressed, the manufacturers of some exposure meters
> will
> acknowledge that they depart from standard calibration
> of their
> meters by incorporating a "K factor." This factor is
> supposed to
> give a higher percentage of acceptable images under
> average
> conditions than a meter calibrated exactly to an 18
> percent
> reflectance. The practical effect of the K factor is
> that if we
> make a careful reading from a middle-gray surface and
> expose as
> indicated, the result will not be exactly a middle
> gray!'
>
> So far so good. This just indicates that the master also
> was aware
> of the same thing that Thom Hogan and others have
> observed, that
> "meters don't see 18% gray" (
> * w w w .bythom . com /graycards.htm ).
>
> However, Adams goes om to say:
>
> With nearly all meters, this factor is equivalent to
> giving a
> one-third stop /increase/ in exposure.
>
> And it is not just a typo, on pp. 66-67 in the same book,
> Adams
> suggest that the photographer compensate for the K-factor
> upping the
> ASA dialed in the meter. By example, he said tha one
> should set ASA 80
> on the meter when shooting ASA 64 film. This, of course
> has the same
> effect as adjusting exposure by -1/3 EV.
>
> The reason I am puzzled by this, is because careful
> metering of
> a Kodak 18% grey card with a Sekonic L-778 spot meter
> confirms
> that the meter doesn't see 18% grey, but the offset result
> in
> about 1/2 stop /decrease/ in exposure, not an /increase/
> as
> suggested by Adams. (I've checked this with other meters,
> and while readings differ by about +-1/6 EV, they all show
> a
> decrease with respect to a reading that would have placed
> the card at middle gray.
>
> And indeed, the instructions that came with my Kodak grey
> card said:
>
> For subjects of normal reflectance increase the
> indicated exposure
> by 1/2 stop.
>
> Kodak's instructions fits my observations exactly
> (if "normal reflectance" = "18% grey").
>
> So ...
> To me it looks like Adams somehow managed to get the bit
> about
> teh K Factor backwards.
>
> The reason I am posting this here is basically to get some
> second opinions on this. Did the great one bungle this
> particular
> detail, or is there something that I've misunderstood?
> --
> - gisle hannemyr [ gisle{at}hannemyr.no -
> * hannemyr . com /photo/ ]
There are a couple of things to beware of here. First,
the only K factor I can find in the standard for calibrating
exposure meters is a correction applied to reflected light
meters for the color temperature of the light used for
calibration. The values given in the old ASA standard are:
For incident light meters, K = 3.6 +/- 0.53 for 2850K and K
= 3.33 +/- 0.50 for 4700K.
For reflected light meters the constant is called C and is;
C = 22 +/- 5 for 2850K and C = 20.8 +/- 5 for 4700K. This is
probably for Selenium cell meters. Cds and other types of
cells have different spectral sensitivity from Selenium so
the factors are likely different. I do not have a copy of
the current ISO-ANSI standard.
Another factor is the fact that gray cards are seldom
perfect Lambertian surfaces, that is, perfectly diffusing,
so that the angle of incidence of the source light will make
a difference in the reflectivity. In addition, many gray
cards have a considerable amount of specular reflection so
care must be used in avoiding them. Ideally, the light
source should be at a 45 degree angle to the card and
reading made on axis.
Another factor to take into account is that gray values
in a negative-positive system are quite relative. Even if
the film and paper had a completely linear relationship
between exposure and density the contrast would be variable.
The usual target is to get a print with a gamma of about 1.0
over the limited range of brightness it can reproduce. This
is still true where the range of brightness is greater as in
a back illuminated transparency or a projected image.
Note that the 18% value is an approximation of "average"
reflectance of an "average" scene and may be pretty far off
for many scenes.
Another factor is that there really is no such thing as
perfect exposure for a negative. The idea is to get the
range of brightness that one wants to reproduce onto the
characteristic curve of the film over an interaval where the
contrast is fairly constant. That means avoiding the toe or
shoulder. Avoiding the toe is easy, just give the film
enough exposure. Most modern films have a very long range
between the minimum for good shadow detail and the shoulder.
Usually the shoulder is not significant for normal subjects.
Reversal processes are much more critical of exposure
because they are nearly always processed for the greatest
range of density the material is capable of. About the only
exception to this are reversal materials intended for
duplication. The speed measuring standards for reversal
materials are different from those used for negatives and
are intended to get the exposure in the right range for
reversal.
Note also that there are other standars that apply to
B&W negative film used in various applications. The same
film may not have the same ISO speed when measured by these
standards. For instance, the standard for motion picture
film is different from that for still film and generally
yields a lower speed.
I just checked two meters I have that take both incident
and reflected light readings. These are a Luna-Pro and the
Sekonic version of the old Norwood meter. Both were measured
in direct sunlight using an 18% gray card with the sun at
about a 45 degree angle.for incident readings the domes of
both meters were pointed straight in the direction the card
was facing. The result was a very close agreement for both
types of readings for both meters. Of course, the
reflectance of the card is of no importance here because the
reading will be the same regardles of it.
I am not sure what Adams had in mind but I can say that
the ISO standard for B&W still film is intended to yeild the
_lowest_ exposure that will result in good shadow detail.
The idea is that thin negatives tend to have less grain and
better sharpness than denser ones. However, from the
standpoint of tone reproduction a bit more exposure often
results in an improvement.
--
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix . net com . com
--
Posted via a free Usenet account from * w w w .teranews . com
"Gisle Hannemyr" <gisle+news@ifi.uio.no> wrote in message
news:q5tzvp7f7v.fsf@kaksi.ifi.uio.no...
> When re-reading Ansel Adams' "The Negative", I came across
> by the
> following paragraph, which appears on pp. 42-43 in the
> 2002 editions,
> whivh I belive is a reprint of the 1981 edition:
>
> 'If pressed, the manufacturers of some exposure meters
> will
> acknowledge that they depart from standard calibration
> of their
> meters by incorporating a "K factor." This factor is
> supposed to
> give a higher percentage of acceptable images under
> average
> conditions than a meter calibrated exactly to an 18
> percent
> reflectance. The practical effect of the K factor is
> that if we
> make a careful reading from a middle-gray surface and
> expose as
> indicated, the result will not be exactly a middle
> gray!'
>
> So far so good. This just indicates that the master also
> was aware
> of the same thing that Thom Hogan and others have
> observed, that
> "meters don't see 18% gray" (
> * w w w .bythom . com /graycards.htm ).
>
> However, Adams goes om to say:
>
> With nearly all meters, this factor is equivalent to
> giving a
> one-third stop /increase/ in exposure.
>
> And it is not just a typo, on pp. 66-67 in the same book,
> Adams
> suggest that the photographer compensate for the K-factor
> upping the
> ASA dialed in the meter. By example, he said tha one
> should set ASA 80
> on the meter when shooting ASA 64 film. This, of course
> has the same
> effect as adjusting exposure by -1/3 EV.
>
> The reason I am puzzled by this, is because careful
> metering of
> a Kodak 18% grey card with a Sekonic L-778 spot meter
> confirms
> that the meter doesn't see 18% grey, but the offset result
> in
> about 1/2 stop /decrease/ in exposure, not an /increase/
> as
> suggested by Adams. (I've checked this with other meters,
> and while readings differ by about +-1/6 EV, they all show
> a
> decrease with respect to a reading that would have placed
> the card at middle gray.
>
> And indeed, the instructions that came with my Kodak grey
> card said:
>
> For subjects of normal reflectance increase the
> indicated exposure
> by 1/2 stop.
>
> Kodak's instructions fits my observations exactly
> (if "normal reflectance" = "18% grey").
>
> So ...
> To me it looks like Adams somehow managed to get the bit
> about
> teh K Factor backwards.
>
> The reason I am posting this here is basically to get some
> second opinions on this. Did the great one bungle this
> particular
> detail, or is there something that I've misunderstood?
> --
> - gisle hannemyr [ gisle{at}hannemyr.no -
> * hannemyr . com /photo/ ]
There are a couple of things to beware of here. First,
the only K factor I can find in the standard for calibrating
exposure meters is a correction applied to reflected light
meters for the color temperature of the light used for
calibration. The values given in the old ASA standard are:
For incident light meters, K = 3.6 +/- 0.53 for 2850K and K
= 3.33 +/- 0.50 for 4700K.
For reflected light meters the constant is called C and is;
C = 22 +/- 5 for 2850K and C = 20.8 +/- 5 for 4700K. This is
probably for Selenium cell meters. Cds and other types of
cells have different spectral sensitivity from Selenium so
the factors are likely different. I do not have a copy of
the current ISO-ANSI standard.
Another factor is the fact that gray cards are seldom
perfect Lambertian surfaces, that is, perfectly diffusing,
so that the angle of incidence of the source light will make
a difference in the reflectivity. In addition, many gray
cards have a considerable amount of specular reflection so
care must be used in avoiding them. Ideally, the light
source should be at a 45 degree angle to the card and
reading made on axis.
Another factor to take into account is that gray values
in a negative-positive system are quite relative. Even if
the film and paper had a completely linear relationship
between exposure and density the contrast would be variable.
The usual target is to get a print with a gamma of about 1.0
over the limited range of brightness it can reproduce. This
is still true where the range of brightness is greater as in
a back illuminated transparency or a projected image.
Note that the 18% value is an approximation of "average"
reflectance of an "average" scene and may be pretty far off
for many scenes.
Another factor is that there really is no such thing as
perfect exposure for a negative. The idea is to get the
range of brightness that one wants to reproduce onto the
characteristic curve of the film over an interaval where the
contrast is fairly constant. That means avoiding the toe or
shoulder. Avoiding the toe is easy, just give the film
enough exposure. Most modern films have a very long range
between the minimum for good shadow detail and the shoulder.
Usually the shoulder is not significant for normal subjects.
Reversal processes are much more critical of exposure
because they are nearly always processed for the greatest
range of density the material is capable of. About the only
exception to this are reversal materials intended for
duplication. The speed measuring standards for reversal
materials are different from those used for negatives and
are intended to get the exposure in the right range for
reversal.
Note also that there are other standars that apply to
B&W negative film used in various applications. The same
film may not have the same ISO speed when measured by these
standards. For instance, the standard for motion picture
film is different from that for still film and generally
yields a lower speed.
I just checked two meters I have that take both incident
and reflected light readings. These are a Luna-Pro and the
Sekonic version of the old Norwood meter. Both were measured
in direct sunlight using an 18% gray card with the sun at
about a 45 degree angle.for incident readings the domes of
both meters were pointed straight in the direction the card
was facing. The result was a very close agreement for both
types of readings for both meters. Of course, the
reflectance of the card is of no importance here because the
reading will be the same regardles of it.
I am not sure what Adams had in mind but I can say that
the ISO standard for B&W still film is intended to yeild the
_lowest_ exposure that will result in good shadow detail.
The idea is that thin negatives tend to have less grain and
better sharpness than denser ones. However, from the
standpoint of tone reproduction a bit more exposure often
results in an improvement.
--
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Richard Knoppow
Los Angeles, CA, USA
dickburk@ix . net com . com
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