As one who has both dedicated film scanners and flat bed scanners I will
give you real world advice.
Yes, if you must have the best quality 35mm scan a film scanner is the way
to go.
However Epson makes some reasonably priced flatbed scanners with built in
transparency units that will do an excellent job on your medium format film
and actually a reasonably good job on 35mm materials. I would recommend you
start here and if you are not satisfied with scans of the 35mm originals you
will have to invest in dedicated film scanner.
In order to get the best scans you have to ensure flatness, sometimes with a
piece of glass over the film. Even so a certain amount of software
sharpening will be necessary for optimal printing.
While a dedicated film scanner at 2000-2400 dpi should easily yield scans
that enlarge to 11 inches and greater with a flatbed scanner you should scan
35mm materials at the highest dpi you can.
You must understand that you will have to do some fixing of the scans in an
imaging program to optimize the images in terms of color, contrast, etc.
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