RE: filmscanners: Scanner resolution (was: BWP seeks scanner)

["Austin Franklin" <darkroom@ix.netcom.com>]

> One of the things that has always struck me about my 4000 ppi
> scanned images is how much sharper the dust is than any image
> detail on the film - even films like Provia 100F.  This implies
> to me that the film itself is the limiting factor for "image
> sharpness".  While we might all like to see 8000 ppi scanners for
> a number of reasons, we won't actually resolve much more image
> content that the current 4000 ppi models are providing.
>
> After all, 4000 ppi gives a resolution of 75 lp/mm or so, and it
> takes pretty remarkable technique to actually get that kind of
> resolution onto film.  Or is my crude first-approximation
> assessment incorrect, and we actually can't resolve detail in the
> scan at more than half that - say 40 lp/mm with reasonable
> contrast?  Even that level is still sufficient for prints that
> appear "sharp" at normal viewing distances.

Typically, B&W is far sharper than color negative film, which is typically
sharper than chrome film (because of the double development which softens
the edges further).  Also, take a good look at your different channels.  If
you have a CCD scanner, you will find the red channel is soft.  This is for
two reasons.  One is smear, and the second is intensity.  Red "bleeds"
across to adjacent cells, and it also "blooms".  Both of these effects will
cause red to be fuzzy.

I'd suggest taking a good look at a decent B&W negative.

If you are going to be making B&W scans from a tri-color CCD scanner, don't
let the scanner do the B&W unless it does not use the red channel.  I'd
strongly recommend doing the conversion your self from either the blue
and/or green channel, and not use the red channel at all.