filmscanners: Scanner resolution (was: BWP seeks scanner)

[Paul Chefurka <Paul_Chefurka@pmc-sierra.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.

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.

Paul Chefurka

-----Original Message-----
From: Raphael Bustin [mailto:rafeb@channel1.com]
Sent: Friday, June 15, 2001 7:13 AM
To: filmscanners@halftone.co.uk
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 
resolution.

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.



rafe b.