From: Sam Wang (stwang@mindspring.com)
Date: 04/17/00-09:42:55 PM Z
At 10:22 PM -0400 4/17/00, Robert W. Schramm wrote:
>>I am glad someone agrees with me on this. I perhaps had my numbers off
>>but I was in the ball park. Color positives - 8:1 to 16:1
>>B & W. Negatives - 64:1 to 144:1.
>>I had saidthat this came from several textbooks and Sil asked me
>>what the references were. I did spend about a hour today looking
>>but never found them. When I quit teaching 2 years ago, I gave a lot
>>of books away to students. Anyway, without the references I am sure
>>this is correct. If you think about it, tonal range is related to
>>latitude. It is a well known fact that color positives have a
>>latitute of only about +- 1/2 a stop. By comparison, a B & W negative
>>film can have a latitude of +- 2 or 3 stops and thus a greater tonal range.
Bob,
If we are talking about EXPOSURE range, you are right. But I thought
the subject was DENSITY RANGE. Color transparencies have much greater
density range, on the order of 3.0 or so, whereas typical density
range of platinum negatives runs about 1.75.
I agree with Tom Ferguson that to make BW negatives from color
transparencies for PD/PT, or for any other alt process, is a breeze.
You can tailor the exposure/development for just the density range
you need.
Sam Wang
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