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Old Mar 2, 2005, 10:04 AM   #1
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I want to scan a wedding picture that is 5x7 and then print it at 11x14 . Do I scan the picture at the maximum that the scanner can do (epson 4180) and then go to Qimage and set the print size of 11x14 there,or is it best to scan the original 5x7 to 11x14 and then go to Qimage for printing? Thanks
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Old Mar 3, 2005, 1:34 PM   #2
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I would recommend scanning at 600 PPI when you are scanning photographic prints. A photographic print only holds a little more than 300 PPI worth of "information" so scanning at 600 PPI which is double what the print holds is enough to capture all the information in the print itself. Nyquist which says that you must sample at twice the resolution available in the original to get all the detail comes into play here. Once you've made sure that you captured all the information in the print, leave it to the software (Qimage) to interpolate more if needed for larger prints.

Scanning at 600 PPI and then upsampling more if necessary is better than scanning at 1200, 2400, or 4800 PPI because at ridiculously high scan resolutions, you are simply picking up "errors" in the print. In other words, if there is only 300-400 PPI worth of information available in the print itself, going beyond that isn't going to pick up more real data: it's going to pick up defects in the print itself like divits in the paper, uneven chemical distribution, grain, etc. You'll be better off scanning to get all the "real" information and then interpolating up from there because doing so won't accentuate deficiencies in the photographic printing process.

This whole topic might make a good April column for the Tech Corner.

Mike
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Old Mar 3, 2005, 3:38 PM   #3
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If a print should be scanned at around 600 PPI, what resolution should I scan a negative? I'm assuming this will depend on the speed of the film. Will 35mm vs. Medium Format make a difference?

By the way, this would be an excellent topic for your column, Mike.


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