Realizing this is a bit too late, but for those who may read this thread in the future, here's my 2 cents...
I do a lot of solo backpacking with photography as the catalyst/priority, so my entire setup is geared toward it. When backpacking several days with lots of elevation change, really a backpack built for multi-day trips is imperative. I also try to be as lightweight as possible, knowing my camera gear will tack on almost 10 pounds. I've concluded that a comfortable pack is far and away the key ingredient. So here's what I've landed on:
For day trips: the MindShift Rotation 180 pro. Is it expensive? YES. However, it's already paid off when I've been on sand dunes where I don't want to put my pack down (blowing sand in a thunderstorm), and in creeks where the water is wall-to-wall (in the San Juan Mountains). The rotation really does work amazingly well, and it is as comfortable as a backpacking backpack. The suspension is rock solid and it has a legitimate hip belt that carries the load (unlike LowePro "waist straps" that are only meant to help balance the load). I've had 30 pounds in it and it's felt absolutely fine hiking some pretty rugged terrain. I've never experienced a pack quite like it, and I'm absolutely sold on it.
For overnights and multi-day: the Granite Gear Blaze AC 60, with my main camera strapped to the front shoulder straps in a LowePro Toploader 50 AW. I use a 6D with the 16-35 f/4 IS (brilliant lens), which fits snuggly but it's solid. The IS really does work, I've actually taken bracketed shots hand-held using the IS successfully. With the weight of backpacking gear on the back, the camera in front helps balance it all a bit, so that works nicely, and it's readily-accessible since it's right in front.
The Blaze AC 60 is so light it can double as a peak bag, but comfortable and sturdy enough to handle up to 40 pounds (I stay around 33-35 pounds max for 5-6 day trips, which includes the 10 pounds of camera gear). And then whatever you decide for extra lenses and accessories (an ICU, individual lens cases, whatever), it all fits quite nicely in the pack wherever you need it (above food, below food, etc.).
But whatever you do (Blaze AC 60, Osprey, REI, etc.), get a backpack that can handle the weight COMFORTABLY, then improvise on how to get the gear inside. DON'T get a heavy photography backpack with all sorts of pockets and zippers and such, which just adds up the weight.