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filmscanners: Scanner resolution (was: BWP seeks scanner)
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.
Whatever the final outcome may be (once we've worked through the morass of
differences between film and digital image reproduction technology and
information theory) I'm still left with the feeling that current scanner
resolution is getting off the film most of what's actually there. An
order-of-magnitude improvement is probably not available in this system.
From: Raphael Bustin [mailto:email@example.com]
Sent: Friday, June 15, 2001 7:13 AM
Subject: Re: filmscanners: BWP seeks scanner
On Fri, 15 Jun 2001, Arthur Entlich wrote:
> You don't directly mention the size of the prints you wish to produce,
> although you allude with the 870 printer something like 8 x 12" or
> smaller. Unlike silver images, which simply have larger grain making up
> the components of the image, without any true resolution loss, in the
> digital realm, since even 4000 dpi scanners do not capture all that is
> on a 35mm frame, you end up with softness and loss of detail if you go
> too large.
While I know that this topic has been debated
many times, on many forums, I've come to the
conclusion that perhaps that very high estimate
of film resolution may be optimistic.
I've never seen a drum scan of any of my slides
or negatives, but I've seen scans from a large
variety of CCD scanners, including the SprintScan
4000 and now my 8000 ED -- both rated at 4000 dpi.
In a nutshell -- I don't really see a significant
increase in sharpness going from 2700 dpi to 4000
dpi. And this is with slow (ISO 100) negative
films like Reala, Supra, etc, using decent optics
and with the camera on a tripod.
What I do see from these hi-res scanners is lower
noise, and better tonality. With the 8000, I'm
enjoying the extra dynamic range. But I'm not really
seeing a major increase in sharpness or apparent
Maybe one needs to go with fancy German lenses to
see that. Or maybe it's the case that the scanner's
internal optical system is the limiting factor.
Whatever the reason -- my point is that this claim
of "greater than 4000 dpi" for the effective
resolution of film is rather optimistic. I'm curious
what it would take to actually observe and realize
such a high resolution.