Hair Bear said:
Resolution at 300dpi is OK if you are printing at around 1:1 of the file size.
But if you want to enlarge files then you will be needing the extra 'real' res to do it.
FMW, you may not notice the extra because your output device can't show it. That doesn't mean you shouldn't scan at a larger res, it just means you have found 'your' best resluts v time to scan v file size.
If you intended to do larger prints you may need a higher resolution file.
I totally agree with you. I might add here that the image resolution should better be scaled in a way that matches the printer's native resolution. For example, if the printer prints at 300dpi or 600dpi or 1200dpi, the 300dpi picture is fine. For a 360/720/1440dpi printer, I would scale the image at 360dpi for best results.
Now, on to scanning resolution. And bear in mind, we are scanning films, not paper.
The 3,6mm width of the film frame certainly needs to be enlarged. Otherwise, we can only print thumbnails.
Hence, to be able to print a 10x15 picture, we need a 4,2x enlargement. Therefore, the scanning resolution needs to be at least 1200dpi.
If one wants to print a 20x30cm picture, then the enlargement needs to be about 8,3x. This means we need to scan at 2490dpi (or close to that).
This means that in general, a 2700dpi scanner is more than enough.
If we want to be able to crop part of a picture, we need to be able to scan at even higher a resolution.
My suggestion reflects just that, and an additional thought. Scanning and color correcting the negatives is a tedious process, one that you should not want to repeat. Scanning your negatives and preserving on backed-up DVDRs is - for me - preservation and archival. For this purpose, and since 4000dpi scanners are affordable, I would do this job only once, at this resolution and get done with the negatives (well, not throw them away, but not worry whether the colours will fade after some years - and they will do).