For "A" Rank Photos, the enemy subject needs to meet certain criteria:
- Full Frontal: capture with head facing camera, or slightly angled
- Centered: capture whole body centered in frame
- Proper Distance: shot cannot be too zoomed in or too zoomed out
- Critical Status: enemy weakened to critical state
- Boss: bigger enemies are usually valued more
Note: Having a photographer in a store multiplies the value of the photo by 10.
This can usually be accomplished consistently by saving before going to the shop or looking at the photo's and reloading the save one time if a photographer is not in. If you have the patience you can also get the photographer by simply choosing "Sell Photo" then leaving back to the main shop menu if the photographer isn't in, then re-entering the "Sell Photo" option until he is in, it is an estimated 5% chance each time. Also note that selling anything below B rank will get you less from a photographer, almost nothing most of the time. Confirmed on the PS3 version.