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Re: [OM] Copying slides

Subject: Re: [OM] Copying slides
From: Joey Richards <bigjoe@xxxxxxx>
Date: Thu, 10 Feb 2000 10:54:03 -0500
Paul Wallich <pw@xxxxxxxxx> wrote:
> With the current generation of digital camera, it ain't really
> worth it, imo. I've been trying it with a C-2000, and the sharpness and
> dynamic range just aren't there compared to a halfway decent slide scanner.
> The results are too muddy and require too much tweaking, plus bleeding on
> the highlights yadda yadda.(Only 8 bits per color base resolution compared
> to 10 or 12 in scanners) I am sorta thinking of trying again with a camera
> that has B&W mode so I can do a three-filter arrangement...
>

The multipass approach to digital slide copying reminds me of a computer
graphics paper I read not long ago.  Measuring the true lighting from
a scene is difficult because our scanning/photographic processes suffer
from extremely limited dynamic range compared to what's in nature and
what our eye, having an adaptive dynamic range, can pick up.

This paper described a method for generating high dynamic range
photographs.  Basically, they took multiple pictures of a scene with
different shutter speed settings (many stops apart) so some had excellent
shadow detail with totally blown out middles and highlights, and some
had great highlight detail with dark shadows / middles, etc.  Then,
using the exposure information, they combined the multiple shots to
get an extremely high dynamic range image of the scene.

You could do the same thing for digital slide copying -- either by
varying the shutter speed or putting ND filters in front of the
lens; I suspect the former would be preferable.  It might be worth
a try if someone's interested... if you'd like a reference to the
paper, I can try to dig it up.  :)

joey

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