At 20:10 22.03.03, C.H.Ling wrote:
From: "Jan Steinman" <Jan@xxxxxxxxxxxxxx>
>
> Not really. In raw mode, some digicams will give you 10 bits --
essentially 10 stops. Drum scanned Velvia will yield 36db of dynamic
range -- about 14 stops.
I think 36db is a wrong value, most agree slide has D-Range of roughly 4.0,
which is 10000:1 and 80db.
I'll probably regret trying to explain this at the middle of the night, but
C.H.Ling is correct if we talk about the density range of a slide. That
means the difference between the darkest and lightest parts of a slide if
you measure how much light can pass through. That is however not very
interesting if we're trying to compare how many stops a digital camera and
a slide film can *record*. If you look up the film data sheets at Fuji or
Kodak you'll find that about 6 stops (give or take) is mapped into that 4.0
density range.
In other words it's an enormous increase in contrast, going from a ~6 stops
range in reality to a 13-14 stops on film, but the film still depicts 6
stops only. The digital camera would be much more forgiving about exposure
and you could always increase the contrast afterwards by picking 6 stops
from the 10, whereas it would be impossible to get more than 6-7 from a
normal slide film.
There are duplicating films that would map the contrast 1:1, but I don't
think they would quite reach D=4.0. It would be interesting to try some
normal pictures with a film like that and see how the slides would look
when projected. In theory it should look just like reality, but I suspect
it would be very dull, comparable to cheap prints.
Thomas Bryhn
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