Re: Basic question about contrast and gamma

On 24 Feb., 23:29, "Richard Knoppow" <dickb...@[EMAIL PROTECTED]
> wrote:

> Gamma is a measure of the slope of exposure vs: density
> of the straight line ****tion of a film or paper curve. Since
> nearly all film or paper characteristics are curved and have
> either small or no straight line ****tions gamma can be
> misleading about overall contrast. More modern measures are
> average contrast or G-bar and Contrast Index or CI. These
> two are very similar but CI has a specified interval of log
> exposure.
> =A0 =A0 =A0In any case, whether one is using gamma or G-bar or CI
> the numbers combine by multiplying, not addition or
> subtraction. That is, a gamma of 0.5 will combine with a
> gamma of 2.0 to result in a gamma of 1.0. A gamma of 1.0
> means that the contrast is the same as the original subject.

Uuh, now I see what you mean. You talked about the difference between
gamma and contrast index before but I didn=B4t realize it=B4s im****tance -
sorry for the delay! So using the contrast index method leads to other
figures for the negative and the paper and they combine to about 1. So
I finally got rid of this problem I had with the curves of these
materials. - Thank you!
Now there is only one point left from my starting question: Why is
there not such a wide variaty of paper grades in color reproduction as
there is in b&w? As far as I understand, in b&w we need this wide
variaty to make the dark tones of a low contrast negative as black as
the dark ones of a high contrast neg. What=B4s thze difference in color?
Is it because a high density there really means a more saturated color
and not so much a darker color?

Best!
Monica Schulz