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RE: filmscanners: Vuescan long pass mode




Jerry Oostrom wrote:

> Another, complex approach would be to apply scouring algorithm in the long
> exposure scan to the sections with pixels exposed to the limit (one/all
> channels). That is, if scouring algorithm can be applied that way. The
> pixels that were exposed to the limit would still have weighing factor 0,
> but the adjacent pixels could have their normal weighing factor, whatever
> that is.

<SNIP>

I was thinking about this as well.  I suspect that pixel bleeding may occur 
with some 
CCDs even before the highlight levels reach 255,255,255.  (I did a scan of a 
hole in a 
piece of card with my Elite.  The normal scan did lose some edge detail but a 
scan at 
the shortest scan duration showed card fibres at the edge of the hole.)

So an option might be a combination of 3 scans, a short scan to retain highligh 
details 
& minimise/identify pixel bleeding, the normal scan for the majority of the 
pixel data 
and the long scan to minimise noise and maximise shadow detail.  The short scan 
would have to act as a mask to determine which highlight detail is "real" and 
not 
bleeding, could provide detail for any of the highlight detail compromised by 
bleeding in 
the other 2 scans and, for midtones and shadows affected by bleeding, help 
determine 
which of the other scans provides the best data.

Of course, I'm sure it's much more complicated than that and I wouldn't have a 
clue 
how it could all be coded!  Certainly, my own experiments with masks in 
Photoshop 
have never managed to get rid of blooming/reduced contrast around highlights.



Al Bond




 




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