On Sun, 1 Jul 2001 11:25:44 +1000 Rob Geraghty (harper@wordweb.com)
wrote:
> I was wondering if anyone on the list could explain to me chemically
> how it
> is that overexposing a colour negative makes the film grain smaller?
It doesn't:) What happens in that in areas of slight exposure, especially
where only a single colour-sensitive layer is involved (eg dark blue sky),
the dye clouds do not overlap and diffuse each other, which is the case in
more-exposed areas of the image. The few dye-clouds there are thus stick
out like a sore thumb, and give an appearance of worse grain.
This is rather the opposite to conventional B&W silver halide film
behaviour, where increasing exposure causes grains to be larger and clump
together more. In colour neg, the dye clouds are semi-translucent, and
although larger, greater density means more overlaps and more diffusion.
Regards
Tony Sleep
- Online portfolio & exhibit; + film scanner
info & comparisons
