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jeffkrol · 12-01-2008, 08:37 PM

Originally Posted by Marc Sabatella

True. But the problem with colored filters is that most of the situations we are talking about here involve low light levels as it is. A blue filter means it's going to be that much hard to get enough light at all. Of course, one could question whether bad light is better than no light. But I do find that if nothing else, the red channel on its own often makes a fine B&W conversion.

If your going to convert to B&W, losing a stop or 2 of light is somewhat meaningless.
Interesting reference article(s)
White Balance -- Are you RGB Savvy by Moose Peterson
http://www.pochtar.com/NikonWhiteBalanceCoeffs.htm
The dirty secret of WB and pseudo-ISO pushes, and the solution: Nikon D3 - D1 / D700 Forum: Digital Photography Review
When you use a color compensating filter, you suppress the dominant
frequencies of the light, holding them back so they don't overexposure as
you gather the frequencies that *are* underrepresented. High altitude has
too much blue; daylight, too much green; incandescent, too much red.
Choose a color-correcting filter of a density that works for your camera
and light. I believe that Julia has suggested CCM20 may be enough on a D2H
for daylight work, but other numbers for other bodies.

Color Temperature and Color Correction in Photography
http://www.pochtar.com/NikonWhiteBalanceCoeffs.htm

So yes, Jim, you're right: this means a longer exposure. But by color-
correcting your light before it hits your camera, you'll get real data,
not false data created by amplification.

And you might not lose a full 2 stops. True, with a blue-admitting filter,
you'll pay more in exposure because blue contributes least to human
luminance perception, The precise density you'll need varies according to
your model's CFA dyes and shooting light. Maybe an 80A's 2 stops; maybe an
80C's one stop or an 82C's 2/3 stop will suffice to put you where digital
amplification won't cause too much noise.

12-01-2008, 08:37 PM	#8
jeffkrol Pentaxian Location: Wisconsin USA Gallery Photos: 2 Posts: 1,635	Originally Posted by Marc Sabatella True. But the problem with colored filters is that most of the situations we are talking about here involve low light levels as it is. A blue filter means it's going to be that much hard to get enough light at all. Of course, one could question whether bad light is better than no light. But I do find that if nothing else, the red channel on its own often makes a fine B&W conversion. If your going to convert to B&W, losing a stop or 2 of light is somewhat meaningless. Interesting reference article(s) White Balance -- Are you RGB Savvy by Moose Peterson http://www.pochtar.com/NikonWhiteBalanceCoeffs.htm The dirty secret of WB and pseudo-ISO pushes, and the solution: Nikon D3 - D1 / D700 Forum: Digital Photography Review When you use a color compensating filter, you suppress the dominant frequencies of the light, holding them back so they don't overexposure as you gather the frequencies that are underrepresented. High altitude has too much blue; daylight, too much green; incandescent, too much red. Choose a color-correcting filter of a density that works for your camera and light. I believe that Julia has suggested CCM20 may be enough on a D2H for daylight work, but other numbers for other bodies. Color Temperature and Color Correction in Photography http://www.pochtar.com/NikonWhiteBalanceCoeffs.htm So yes, Jim, you're right: this means a longer exposure. But by color- correcting your light before it hits your camera, you'll get real data, not false data created by amplification. And you might not lose a full 2 stops. True, with a blue-admitting filter, you'll pay more in exposure because blue contributes least to human luminance perception, The precise density you'll need varies according to your model's CFA dyes and shooting light. Maybe an 80A's 2 stops; maybe an 80C's one stop or an 82C's 2/3 stop will suffice to put you where digital amplification won't cause too much noise.