Mark,
if these are different hardware scans (and not different scans - from disk -
of the same raw file), the fact that the "noise" has exactly the same
pattern in both pictures indicates that it is *not* noise (which is random),
and it is more visible in the picture with bp=1% simply because that picture
is a bit brighter (or, at least, it appears brighter on my monitor).
If they are not, I'd recommend to make two separate scans of the film an
check again...
Alessandro Pardi
> -----Original Message-----
> From: Mark T. [mailto:markthomasz@ozemail.com.au]
> Sent: venerdì 15 febbraio 2002 12.22
> To: alessandro.pardi@inferentiadnm.com
> Subject: [filmscanners] Blackpoint & noise, was grain
>
>
> Now I'm confused (so what's new)..
>
> Why would adjusting the black point *up* cause noise to
> appear, given that the adjustment I'm making isn't sufficient
> to affect the deep shadow detail? This seems backward to me
> - if I increase the black point, am I not telling the scanner
> to throw away some of my deepest blacks (ie shadow detail),
> and therefore some of the noise (if there was any) should go
> with it..?
>
> I'm seeing the reverse. Well, it's Friday, late, and maybe
> my mind is going..
>
> Anyway, if anyone wants to see what I mean, and can then
> humour me and explain in words of few syllables :-), the
> samples and more info are here:
>
>
>
> (As it may affect your decision to visit, it's about a 270K
> download altogether.)
>
> Thanks for any enlightenment..
>
> mark t
>
> Tony wrote:
> >> (markthomasz..) wrote:
> >
> >> I've noticed that on some transparency films, I get a
> grain-like effect
> >> in shadows when I use a black point other than zero (in
> Vuescan). I
> >> haven't yet looked into exactly what is happening, but the 'noise'
> >> vanishes as soon as I set bp to 0.
> >>
> >> So it is obviously not CCD noise
> >
> >What you describe is very likely CCD noise. On well behaved
> scanners most
> >of it is below the black point on any film you want to scan, on less
> >fortunate models it climbs up toward the midtones and you
> can't just chop
> >it off without sacrificing shadow detail.
> >
> >Regards
> >
> >Tony
>
>
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