Problem with scanning slides

[Bloxham Boy]

I have been trying to scan some old slides using a Nikon Coolscan IV ED. I’ve had it for years but haven’t used it for a while and hence the skills are somewhat rusty to say the least !

The original slides are of good quality and taken in full sun etc. but on scanning and putting them into Photoshop, I’m finding that there are castes on both the skies and the foreground that aren’t present in the original.

Is anyone familiar with this scanner and / or willing to share their basic processing procedure that provides decent reproductions without the need for a lot of tweaking ?

MTIA.
John