In reply to Smelly Fox:
All the dedicated "wilderness camera backpacks" I have looked at before have been heavy, uncomfortable to carry and with downright stupidly designed back systems, compared to normal outdoor packs from the likes of Millet, Deuter and others. Might have changed in the recent years, but I still think a camera bag company can't make a backpack that would be actually good to carry on your back...(I would love to be proven wrong, though!)
I would just get a lightly padded insert or a couple of lens pouches, like others suggested. It's more versatile, you can still put the insert or pouches into a small ultralight summit pack. If on easy terrain, I just attach the camera with my favourite lens via a couple of biners and short cord to my shoulder straps (to take the pain out of my neck). Works a treat and is essentially free and more secure than those overpriced backpack shoulder strap attachment systems as well. The nice thing about lens pouches is that you can just put them together on a sling, and have a lens bandolier for short excursions out of camp.