I do alot of hiking daytrips with my camera gear, so I was in the market for one of those camera packs that has a compartment for camera gear plus a compartment for hiking gear. Well after looking for awhile I never found anything that quite met my needs as the hiking gear compartments were too small, the pack was expensive, and the shoulder and waist straps were too minimal for proper comfort.
So my solution was to modify an regular hiking daypack to suit my needs.
First, I bought a 55litre small overnight backpack, which in my case was this Outbound Canyon 55 litre pack
. I got this one on sale for $55.00. This one works well as it has a bottom sleeping bag compartment with an outside access zipper (where the camera gear compartment will be). It also has 3 side straps for secure tripod placement plus other straps on the back should I want to lash snowshoes to my pack.
Now for the camera gear compartment, I cut 6" wide strips of 1/2" dense closed-cell foam. Thicker ensulite sleeping pads work for this and are quite cheap and widely available at most sporting goods stores.
First I make the outside frame so it looks like an upside-down "U" and ensure that it will fit snugly in the sleeping bag compartment and can still be zippered closed. If you want extra stability, use two layers for the outside part. I used duct tape to put the pieces together as duct tape sticks really well to this stuff. Put lots of duct tape around the outside of your photo gear frame as you wont be seeing this tape anyway.
Next you just cut lengths to tape to the inside; customizing a space for your camera body and whatever lenses you want to include. My gear space holds my Sony A700 with landscape lens attached plus space for 3 other lenses.
My filters and lens brush are attached to my hipbelt for quick and easy access via A lowepro Edit 100 camera bag.
Now I have a very comfortable pack with room for all my camera gear as well as plenty of room for hiking gear and clothing. This particular pack also comes with a rain cover as do many other packs.
Total cost was about 70.00.