DANGER: There have been many reports of a recent update removing some necessary photos from the game for this achievement. If you can, prevent your game from updating if you want to complete it. Otherwise, you might have to wait for a future update to get this achievement.This solution is being written upon the game's release. Conditions may change if more episodes are released in the future.
Hey, so the Photographs aren't all that difficult to find. You'll get a bunch naturally by gaining stars from the various levels. In fact, a prerequisite achievement is this:
The last photo you can unlock with stars comes from getting all stars in the first two episodes. Then there are 5 or 6 photos you must find within the second episode's level select menu. These are not hidden; they are visible in plain sight. Just tap them to pick them up.