> But that's not the same as dynamic range. I assume you're talking about
> negative film which should handle overexposure fairly well. But what
> happened to your shadow areas with the overexposure? If all was
> hunky-dory with a two stop overexposure why doesn't the manufacturer
> rate the film at two stops over. Once again, what do the film
> manufacturers state their dynamic range to be?
If the manufacturer discarded 150 years of photographic history, they
could do what DXO did and redefine the film speed rating to do just
that.
In essence, DXO is claiming that in the world of digital, there is no
such thing as a "mid-tone" so therefore the speed rating should be
determined based on the activation of the first bit. Then they decided
that wasn't good enough so they based it on an arbitrary noise floor.
It's not that DXO is wrong in their testing method. My issue isn't
with that. My issue is with their redefinition of things to suit their
own purposes.
So, why not change the rating of the film? Actually, most of us do.
Knowing, for example, that Ektar has a nasty blue shift in the
shadows, but an unending tolerance to slamming the highlights, must of
us will derate the film a bit. Portra 160NC and 400 both have gobs of
tolerance on both ends so derating the film isn't as important--having
a fast enough shutter speed is more important. But before just
derating the film to make use of the extended highlight tolerance, one
must be aware of the tradeoffs. One big tradeoff is the fact that as
you lean into the shoulder, you are losing tonal separation. There is
no free lunch here. The films behave best in the midtones when shot at
the recommended ISO.
Oh, and if you overexpose the image, your question of what happens to
the shadows? They also overexpose. During the editing stage of the
photograph, you just adjust your exposure and contrast to put those
shadows back where they belong. Classic ETTR.
AG
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