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Filmscanners mailing list archive (filmscanners@halftone.co.uk)

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RE: filmscanners: Noise correction algorithms



I already asked this question to Ed and later to this list, all some time
ago. Ed replied that his algorithms were "of course" already doing such a
thing. Then I asked, where can you set the threshold on black (slides) or
white (negs) for what is considered to be dust and waited... (no answer to
that question).

This reminded me that I should put only one question in a mail (ironically
that was even Ed's suggestion to me, even longer ago), since then it clearly
shows both parties that the other person is not answering / missing that
question. But that is getting OT.

I noticed that the HP S20 software was able to paint e.g. in red all pixels
that were being clipped by current histogram mapping settings. To me this
seemed a handy feature, but no other software took over that idea. It seems
that if you can show the user which data is being clipped or is being
considered pixels-to-be-cleaned cq, IR-opaque-pixels, the user would be able
to precisely control if the correct pixels are cleaned. This would be a good
feature for any owner of a filmscanner without IR. Small problem is that you
have to do a full-resolution pre-view, and the big problem is... well,
unknown to me, but known to Ed and other software manufacturers. Perhaps it
has to do with patents, but what I hear is 'click-toot-toot...' and since I
hear that often I wonder: does anybody understand what I am trying to get
at?

"Bar Bar" applying to the civilized greeks 

;-)



> -----Original Message-----
> From: Lynn Allen [SMTP:lalle@email.com]
> Sent: Saturday, April 28, 2001 5:00 PM
> To:   Filmscanners@halftone.co.uk
> Subject:      filmscanners: Noise correction algorithms
> 
> This question is for Ed, and any other program-savy people who want to
> answer.
> 
> Since dust is always "white" on negs and always "black" on slides, while
> "noise" is usually lighter and "grain" is usually darker than the
> surrounding field of pixels, is this or can it be considered in the
> cleaning
> algorithms?
> 
> This suddenly seems so obvious as I experience the problems more, and I
> wonder what I'm missing that it isn't more easy to deal with. (?) Example:
> red pixels in sky colors, when it isn't sunset, green pixels in skin-tones
> and shadow tones at mid-day. It's very perplexing, because I'm pretty sure
> my scanner or its software is actually "seeing" or at least "interpreting"
> those pixels. I could, of course, be wrong, but that's how it looks to me.
> 
> Best regards--LRA
> 
> 
> -----------------------------------------------
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