David, if I am reading your article correctly, downsampling DOES result in image degradation. Just to make sure, let me ask the question another way, if I scan a piece of film at 2000 dpi and downsample the file to 1000 dpi (no USM or other adjustments), how would it compare to a scan of the same film made at 1000 dpi to begin with?
The question arose during a conference with a client who will be having a number of large scans made for a specific large format output project. They will want to repurpose the scans (obviously) for more conventional output. Some repair and composite work will be done to the images which would be impossible to duplicate on multiple res versions of the same image. Even if retouching were not an issue, I think most people would assume that "scan high and downsample" is the way to go, especially when shooting digital originals.
2000 ppi (not dpi - that's for print) doesn't tell enough about the file size
10x10cm @ 2000 ppi is the same files size as 20x20cm @ 1000 ppi is the same files size as 40x40cm @ 500 ppi
This isn't what you mean though, is it?
I think you mean, will a file of, say 10x10cm @ 2000 ppi be 'worse' when reduced to 5x5cm @ 2000 ppi.
I have found that downsampling doesn't affect the 'visual quality' of work that I have done. The pixel data is changed, and any 'change' from the original cannot be better, pixel-wise. But that doesn't necessarily cause the image to appear worse visually.
That's my perspective on things.
Tariq Dajani
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