Passport picture size?
 

Just went and renewed my passport. Had some photos taken, in accordance with the new biometric standards (face front, no teeth, light background, face/picturesize ratio, etc). So I figured I'd get some extra copies for whenever I need to apply for visas during my trip across Africa.

The photographer then said that he'd be happy to make as many copies as I wanted, but that he couldn't guarantee that they would be valid in the countires I planned to visit. For example, passport photos for US are a bit bigger (dont remember the actuall size), dutch photos must have a dark-grey background etc etc. So he suggested I should check up on that before getting 20 or so copies.

How on earth am I going to get that kind of info?