How to fix screencaps

Okay so everyone encounters this problem but never have I had to deal with it on the scale required with Veronica Mars captures (is that even a sentence?). Anyone who watches knows the range of filters and lighting used on the show and the screencaps are lower quality at best. So how do you VM icon makers (or anyone dealing with similar looking caps). Behind the cut I provided some examples of the caps so you know what I'm talking about.

Thanks for any advice you could provide!

And yes, I know they're all LV caps, :P