[pure-silver] Re: Contrast Index
- From: Myron Gochnauer <goch@xxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Sat, 5 Dec 2009 10:39:10 -0400
On 2009-12-05, at 4:17 AM, Richard Knoppow wrote:
> Contrast index is a Kodak term... The contrast used in the ISO standard for
> speed is a Contrast Index measurement which begins at a point which is at a
> density of log 0.1 above the combined density of the support and emulsion
> fog. The upper density is calculated according to the log-luminance range
> required of the negative.
Perhaps someone could explain why the suggested CI for TMY (T-Max 400) is
higher than other Kodak films, whether long or short toed.
My recollection is that Kodak recommended a CI of 0.56 for diffusion enlargers
printing most films, but 0.60 for TMY alone.
I have always assumed it had something to do with the combination of a very
long straight line "curve" through the midtones and highlights (little or no
shoulder) combined with a moderate toe. But it that were true, it would be
hard to believe that no other Kodak film had a combination of toe & shoulder
that deviated from a CI=0.56 recommendation.
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