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

At 08:49 AM 6/15/2001 -0700, Paul Chefurka wrote:
>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.

Quoting from the July 2001 Popular Photography film scanner review (sidebar 
on p. 58):

"Even the best 4000 ppi scanners we've tested aren't capable of capturing 
all the detail found in a 35mm color original under optimum conditions 
(tripod, mirror lockup, etc.). In our tests, the highest res we've found in 
a 35mm color slide or negative is 77 lp/mm. The best 4000 ppi scanner can 
capture about 60 lp/mm, about 25% lower. But that's perfect, because under 
normal shooting conditions (i.e., handheld instead of tripod mounted), 60 
lp/mm is about the best you'll ever get from an SLR."

Photography by Stan McQueen: http://www.smcqueen.com


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