Digital BW, The Print

At 7:27 pm -0500 1/22/04, Bill Morse wrote:

>I have heard, but cannot personally confirm, that PS as well as many 
>scanning programs over-emphasize the red channel over the green and 
>blue ones, supposedly to "better render" (read emphasize) Caucasian 
>skin tones. I seem to remember something like 50 red, 30 green, and 
>20 blue (don't quote me on these exactly! ;^)


Bill --


As you've noted later in this thread you were referring to 
translating color scans to B&W using canned vs. custom conversions. 
However, I thought that comment on this might still be useful for 
people who are trying to produce optimal B&W portraiture from color 
scans.

I suspect that you incorrectly remembered your ratios and that the 
numbers that Paul gives:


At 4:44 pm -0800 1/22/04, Paul D. DeRocco wrote:

>I tested it using a gamma=1 color space, and Image->Mode->Grayscale 
>weighs them 80, 160 and 15 (out of 255), so it's green that gets the 
>strongest emphasis.


(which translate to approximately 31.37 red, 62.75 green, 5.88 blue) 
are more accurate.

The reason I make this assertion is that it used to be so common as 
to be almost standard to use a green filter when doing B&W 
portraiture. (I'm sorry, but I do not remember the filter number; it 
was one of the standard Kodak filters.)

I think that experimenting with a strong green channel is probably 
still the best idea when converting color portraiture to B&W. The 
green filter didn't so much "better render Caucasian skin tones" as 
provide a pleasing rendering of the skin tones while washing out 
pimples and blotchiness. For a more high-contrast look (pseudo Alfred 
Steiglitz?) I'd up the blue at the expense of (primarily) the red.

Paul also said:


>However, the default settings in Channel Mixer are 100,0,0, which I 
>suspect is to make blue skies dark.


This would probably be a good starting point for translating color 
landscapes into striking B&W, but I think that it would be an 
absolute disaster if you had any Caucasians in the picture. It would 
probably be a bad idea when rendering almost any skin tone.

Skin tones run a huge gamut, from the blue-black to the 
chocolate-brown, from the gold-tanned to the pinkish-red, from the 
stark-white to the neon-red and the purplish-red, from the sallow 
yellow to the neon bronze, to the many hues that are as far beyond 
dichotomy as they are from descriptive quantization.

Nevertheless, if I might make a few over-generalizations, based on 
cultural generalities and meaning no offence to anyone:

For Asians I would still leave the green predominate and play with 
the blue at the expense of both the red and the green. For Blacks I 
would watch what happens when starting from the same point and adding 
a healthy dose of the red channel while using the blue to trim the 
contrast. If the skin tone is very dark the blue channel might be 
used to significant effect.


-=-Dennis


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