I'm new to scanning. After getting back some 6x12 color negatives from a pro lab, I scanned them and began dust removal in Photoshop. I see a bunch of clearish, worm-like objects in many places on the film. They are large enough that I have to remove them to prevent them showing in the print.
Also, I recently used Sam's Club (a big mistake) for some 120 film, and the negatives had the same worm-like objects and a great many pock like marks all over the place. They do not look like dust marks. More like damage marks. I'm spending hours on a single negative to clean them up.
What causes these marks?