A few thoughts
1) Most camera back packs have little to no room for other items. They are very focused around holding camera gear which means if you've got to get all your other supplies in there as well then you will run out of space very fast. If you are not far from a car that's fine, but if you're properly camping a long way of into the wildernes then chances are you want bag dedicated to your survival gear and supplies FIRST and FOREMOST.
2) Camera backpacks are great, but honestly they are not magical. Which is to say that if your lens is in the padded case it came with, or is in a case or wrapped in a good few clothes chances are its pretty safe. Ergo pack it well and it should be fine.
Make sure nothing will bang into your gear; make sure that its well away from water and any meths or other liquid fuel you might have for fires (I recall being taught that you put a bag liner in your bag and outside the liner you put your meths bottle and inside the liner you put all your dry items - thus if you get a leak it only affects the bag not your clothes, food, supplies.
3) If you are operating from one single camping site chances are you can take a smaller bag along with you, something that might even be empty on your main journey to and from the camp site; but which you can transfer your camera gear into for your daily trips out away from the camp site. This just makes things more practical than lugging around a huge bag all the time and means you can leave your main gear bagged up at your campsite day to day.
In general your survival gear has to come first when it comes ot fitting the gear in; followed by your comfort. Dedicated hiking backpacks are well made to distribute weight and provide many access pockets and strap points to fit things like sleeping bags on the outside etc.... Most camera backpacks which are heavy duty are basically a box design made to hold camera gear; they can have some great harnesses, but will be really poor for stashing regular camping gear