Agree with other posters that you need to buy a decent scanner.

I would look for a second hand Epson 4990 flatbed scanner, which will do an excellent job with medium format negs and a satisfactory job with 35mm. I traded up from a lesser Epson to the 4990 and was then faced with the task of re-scanning all of my stuff, the improvement in quality was worth it.

A flatbed scanner would probably not be an acceptable solution for a professional user, certainly for 35mm film, but the dedicated film scanners are much more expensive. (I guess that very few pros use 35mm film these days.

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A major problem is holding the film flat, and the supplied negative holders are far from perfect.

A final thought, I find it much easier to scan colour reversal rather than colour negative film, perhaps because the negative film comes with a colour mask. On the other hand B&W negatives scan a treat