Took this from a
Field & Stream article...
Eyes: Despite stories of gobblers' being scared off by the blink of an eye, the wild turkey's vision is no more acute than our own. This reputation is probably based more on their extreme skittishness. The slightest motion that it cannot identify will send it bolting.
Their eyes are on the side of their head, and hence they lack good depth perception. They see in at least trichromatic vision, and the oil pigments in their eyes are under investigation. I have a paper on my desk that is looking at the light retention and light induction properties. Some experts believe that they can see in quadromatic vision, visualizing UV. Hence, that's why they can pick a flea out of black soil, they can detect the movement due to the differences in color.
I haven't run across any papers/studies that have looked at the distance of a turkey's vision...