The 511 push pack WOULD carry your camera and you could put an extra lens in one of the side pouches. I carry a 28 ounce Stainless water bottle in one of the side pouches of mine. I did have a 1 liter Stainless bottle setting in a Stainless cup but it was actually to big for the side pouch and didn't set in it very well so I went to the smaller bottle.

The Fatboy won't carry a bottle (unless you put it inside the main pouch), but is sized really well for a "Man Purse" whereas the 511 is more for a light dayhike bag, holding a couple sandwiches, water bottle fire gear etc.