4000 spi Scans

For standard output sizes as 5"x7" you have to downsize a 4000 spi scan remarkably. This leads to the unwanted effect, that image noise and grain can be amplified. Especially when using Nikon scanners with their harsh LED-light you achieve a better result, when just scanning in 2000 spi. This effect can vary between different manufacturers, though.

By rescaling in Photoshop after the scan you cannot reproduce this. Actually for archival purposes I scan almost exclusively with 2000 spi. If you are not professional photographer with superior equipment plus (!) topnotch skills, your slides will most probably not contain more than 2000 spi quality. 

Please be aware that this recommendation is for top end film scanners like Nikon that actually deliver 4000 spi when they claim it on the package. For flatbed scanners that achieve roughly 30% of their nominal resolution it's a different story.