An expensive camera is a tool. It can blind a monster when applied and even make them attempt to flee. Affected monsters will become blinded for 1d50 turns if adjacent, or much less if they are farther away from you. The flash will also cause a little damage to gremlins. It is useful against the Riders since it is the only item that can make them flee from you. Blinding a monster will negate its fear of Elbereth. You can zap a camera at yourself to blind yourself for 1d25 turns. A cursed camera will blind you half of the time anyway, although this is probably only a concern for cameras found in bones piles.