> > OK, here's my question -- Ariel says he wants to do digital. I've
> > read
> > "regular" sensitometry, the usual suspects including this one, but
> > I'm not
> > sure any of them are the best approach to DIGITAL negatives. I
> > suppose the
> > general info is useful, but nobody has all the time in the world.
> > Wouldn't some kind of computer-digital approach be a better start?
> >
> > J.
> Actually all the basic info should apply, if one can read a HD curve
> one can
> decipher how adjusting the "curves" in PS works....digital scanning is
> founded on the same stuff as film exposing.
Although there is some basic truth in this - I've been using
Photoshop curves to teach photographers about film curves for some
years (yes, with most students it comes that way now) - you've got to
bear in mind at least one very basic difference, which is that with
digital there is an absolute cut-off at both ends of the scale.
This is most noticeable when you over-expose highlights. On film, this
mainly means you have to stand around for rather a long time in the
darkroom burning them in. In digital there is simply no information there
to be recovered. You have to learn to peg the detailed highlights to the
top end of the scale but not let them go over. Zero real over-exposure
latitude, although jpeg/tiff output may not make use of the full scale
and so seem to allow some in processing your raw files.
The camera manufacturers don't seem to have realised this when designing
current models, which have inherited their exposure systems from film
models (certainly this is so with Canon and Nikon, I haven't tested the
other DSLRs now available.)
At the underexposure end the reactions are more similar - we all know you
can't expect much from clear film! However digital does record more into
the shadows than film, which is probably why we get much improved low
light capability compared to film, which came as a surprise to me when I
got involved practically using a DSLR.
Peter Marshall
Photography Guide at About http://photography.about.com/
email: photography.guide@about.com
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Received on Tue Dec 16 08:27:32 2003
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