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[OM] Re: Scanners

Subject: [OM] Re: Scanners
From: Moose <olymoose@xxxxxxxxxxxxxxx>
Date: Tue, 23 Nov 2004 20:53:52 -0800
Piers Hemy wrote:

>It was certainly my understanding that ICE did not work on Kodachromes, *until
>I tried it* - I was amazed at the results from scanning mouldy old slides.
>
>I posted on 6 August "I have had some stunning success scanning pre-1960
>Kodachromes *with ICE* in
>that the fungus and scratches simply vanish without obvious harm to the rest
>of the image.  But there have been some frames where the use of ICE has
>introduced a colour shift which is not pleasant.  
>
>On balance (and greatly to my surprise), ICE was better than nothing on many
>of the Kodachromes - and of course on non-Kodachrome, no question. "
>
The problem with ICE (and Can*n's FARE) on Kodachrome and B&W is simple. 
Both systems are hardware based, with a separate scan being taken in 
infrared to identify areas with dust, etc., which don't let IR through, 
vs. the rest of the image, which does. The silver remaining in B&W negs 
and the dyes in Kodachrome are opaque to IR. So the general caveat that 
ICE doesn't work with them is really more subtle. The effectiveness of 
this technique is in inverse (but probably non-linear) relationship to 
the density of the film image.

So in clear and light areas on a slide, the system may be able to 
differentiate between foreign material and image, depending on the 
foreign matter and image color/density. In the case of image10, the fact 
that the mold is opaque to IR and appears to be a surface overlay, 
rather than emulsion eater, makes ICE quite effective in the important, 
lighter colored parts of the image. If you look closely at the image of 
the girl's coat, you will notice the ICE has had no effect on the vague 
'stuff' mostly on the viewer's left and a whitish blob next to her left 
armpit. That's because the coat is dark enough to defeat ICE.

The effect is stronger and opposite for B&W negs, being most effective 
in shadow areas and less effective overall because silver is more opaque 
to IR than the Kodachrome dyes.

Moose



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