Really easy to get at the beginning.
After wrastlin' some zombies, Frank wants nothing more than to get out of the arena.
On the way, he snoops on TK and Brandon Whitaker having a conversation. After some chatting and TK gives Brandon an armload of TNT, they go between some crates and continue gearing up.
Taking a pic here (by holding LT, pressing RB, and using X) will reward you with over 1000PP and the achievement.
Don't worry if you don't get this exact one. There're a couple instances before and one afterward that can still net you the achievement, and many more opportunities later.
some instances for example.
TK and Brandon's deal, LaShawndra and Gordon's kiss, Antonio eating "chicken" (if you photograph him eating with his back to the Zombies, zoomed in so his face and the "chicken" are in full frame, you'll easily get over 1000 PP)