Backpacks are like shoes: one size does NOT filt all. Unless you plan on tumbling down a mountain with your pack on, forget the photo backpacks - IMHO thay are all to uncomfortable and bulky. Those same packs are wonderful for carrying gear on an airplane, bus or train.

If you're really going to haul gear on your back for miles, then start with a pack that fits you and feels comfortable. Next figure ways to protect your gear while in the pack and learn how to pack the load so that it carries properly. If you pick the pack first, then learn how to pack it, you'll be rewarded with many hours of hiking and not hating yourself, or LF photography.

My current pack is a Mountainsmith that fits my torso and I regularly carry 40-50 pound loads and don't hate myself for doing it. Before getting this pack I used another Mountainsmith pack that didn't quite fit me, but was inexpensive and I hated carrying loads heavier than 20 lbs. Fit is paramount, loading is second, I suggest you go to a store and try some packs then make a decision.

Regards, Pete