camera critter <thcaadoc RemoveThis @hotmail.com> wrote:
> Does anyone have any numbers (RMS or MTF) to show how much the
> resolution and sharpness of color negative film (print film)
> deteriorates when the film is over-exposed by 1 or 2 stops?
Datasheets of movie film graph both grainyness and sharpness
against ISO exposure value, but I've never seen that for still film.
> For example, exposing 100 speed film at EI=50, exposing 400 speed film
> at EI=100 and EI=200, exposing 800 speed film at EI=400 and EI=200.
It depends on the film. Steve Dunn did a study with Supra 400
(IIRC) and decided it lost sharpness at 100 but not much at 200.
When testing a film I try bracketing to see the grain/sharpness
tradeoff. Grain often improves at +.3 EV but sharpness doesn't
usually suffer until way beyond that.
> Overexposure of color negative film (but not b&w negative film) is
> reputed to decrease the perceived graininess because its dye clouds
> overlap more, but I suspect that some tradeoff probably is paid in
> decreased resolution and sharpness. I understand that negative films
> give better sharpness when slightly underexposed.
I'd say that most negative films attain optimal sharpness when
correctly exposed. When underexposed, they grain up (especially
in shadows) thus reducing acutance.<!-- ~MESSAGE_AFTER~ -->
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