So what's the trick?
I've tried several different slabs and they all have the same glares in almost the same places.
I've also tried putting something under different edges of the slab to angle it on the glass.
I can't get rid of the glare.
Im not sure. I do occasionally get the glare at the bottom (only on new wells), but only when i scan on the lowest settings for registry scans. I do my scanning straight from photoshop, since my hp software wont work at all anymore. Regardless, ive never gotten glare in the middle....
One theory i have is some sort of grease/grime/film on the inside of the scanning glass. Mine is starting to show signs of something accumulating on the inside, maybe yours is farther along and causing the light to refract? Just a thought. One day i will clean mine, but it looks like a PITA.