Scanning takes a lot of time so I don't want to find myself in a situation where I have to scan a negative again to make a larger print. So I scan it the first time at as high a resolution in spi as practical, determined by computer processor speed, disk storage space, etc. so that all (or as much as possible) of the detail is captured. With medium format negatives of 6X7 cm or 6X9 cm one generally has plenty of speed and storage space to scan at the highest optical resolution. What I then do is make all of the corrections on this master file and archive it. I can then downsize it to whatever I want for printing.
As has been mentioned before, some of the high quality medium format optics can resolve 100 lp/pm so even a scan at 4000 dpi will not necessarily capture all of the detail in a negative made on high resolution film like Tmax-100 or Acros.
Sandy King
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