> It does mean that low contrast film is an
> inherently better choice, all other things equal, for those who
> digitally process and print their images.
Surely that's only true if you have an infinitely sensitive scanner or if
the higher-contrast film is actually clipping?
Say, for the sake of argument, you have a scanner which has 256 levels of
resolution between black and white. (possibly pessimistic, but I don't know
how well the rest of the steps along the line will preserve higher colour
resolution)
Say the original image ranges from [1] 1 to 1000 "light".
High contrast film maps, say, 1..100 to pure black (call this 0 on the
film), 100..900 to the range of the film, 900..1000 to 1 on the film.
Low contrast film maps, say, 10 to .2 on the film, 1000 to .8 on the film
-- plenty of spare room at the top and bottom end.
Now let's work out what happens when we scan these:
high-contrast; original 'light' 1..100 -> 0, 100..900 -> 0..256, 900..1000
-> 256.
You've lost the top and bottom end, but you have 256 levels of grey in the
middle; each level of grey in the scan maps to 3.9 levels of light in the
original scene (ignoring loss of highlight/shadow).
low-contrast; original 'light' 1..100 -> 51->205. You have all the light,
but only 154 levels of grey in the middle; each level of grey in the scan
maps to 6.5 levels of light in the original scene.
So either way you lose something -- it's just a matter of if it's more
important to preserve highlights/shadows or smooth graduations in the
midrange.
The original point is still fair enough, though; if you have a more
sensitive scanner, then the loss of detail in the midrange will be smaller,
and eventually you won't be able to tell it's not there any more -- but are
scanners (and the rest of the chain of image processing) that good yet? I
don't know, to be honest.
-- dan
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