5000ppi would end up with approx 25,000 pixels in the long dimension -- and that would be huge indeed. Assuming you wish to print that to approx 25" then you'd have over 1000 pixels per inch at output, which is far more than any digital printer can deliver. This is clearly a case of overscanning.
The ideal for you would be 25" * 300dpi = 7500 pixels. Given a 5" negative that translates into 1500ppi scan (i.e. 7500/5), not 5000ppi. Personally, I'd suggest scanning at 2000-2400ppi giving you "archive quality" data and downsample in Photoshop as needed for each particular print size.
Michael
-----Original Message-----
From: dmoore [mailto:dmoore007@xxxxxxxxxxxx]
Sent: Sunday, December 7, 2008 11:47 AM
To: 'List for Photo/Imaging Educators - Professionals - Students'
Subject: DSLR vs 4x5 film
Thanks everyone for your thoughts and ideas about my DSLR vs 4x5 film conundrum. It is interesting how different your opinions have been, some favoring digital and some film. It seems split down the middle. One thing I want to clear up is that I didn't say, or didn't mean to say that I would be scanning the 4x5 neg at 200PPI. That would be pretty silly. That was the printing resolution I was referring too. For a 20x24" print, I would probably scan the neg at about 5000PPI, so that I could print at about 200PPI. Also, James, you referred to the technique of bracketing exposures on a DSLR and then using the HDR function in Photoshop, in order to increase dynamic range. But what if you are shooting landscape that include clouds? Clouds move, and one would probably end up with blurred clouds. Dave
