I have just started using film again and last week had 2 lots of film processed and just scanned to disk, rather than getting prints and disk.

The images on the disk were grainy and I was unable to zoom on any of them without getting rubbish.

Previous scans were much better quality

The scans from last week were done at 600dpi and the previous ones were 72 dpi

I don't know enough about the scanning to be able to ask the photo shop to do anything specific

What should I ask for, what is the best resolution to use ?
Thank you