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Re: tank picture: overexposed upper leaves

On Tue, 27 Feb 2001, Ivo Busko wrote:
> The best way IMO is to use a high-end digital camera. Digital cameras
> use charge-coupled devices (CCDs) in place of photographic film. 
> CCDs have typically a much wider dynamic range than film. I have
> pictures of my tanks taken with both methods, and the difference is
> amazing.

Sorry, Ivo, that just ain't true!  CCD's have a significantly lower
dynamic range than photographic film.   Maybe it's easier to CONTROL a
digital camera, but there is definitely a lot less information stored on
those CCDs (especially if it's a 24-bit color image) than on the
equivalent piece of celluloid.  When I was getting my degree, we did a lot
of work with X-ray and photographic emulsion for recording densitometry,
and all the available CCDs saturated WAY below the levels we needed.
There are films with excellent latitude that can be overexposed by several
stops and still produce a good quality print.

Anyway, to add my experience to this, I can often correct some of these
problems by retouching (aka good old dodging & burning) the picture
afterwards on the scan.  I've seen some folks (like Olga Betts) use
fill-in lights to add a little more to the areas that get shaded by the
top light.

  - Erik

Erik Olson
erik at thekrib dot com