All photographers need tools. Away from home, a hotel stay invites a big toolset; a car camp likewise. A large-volume sea kayak can carry the gear you need. With backpacking — or with minimalist-type sea kayaking — it's essentials only. Below are two lists, for the Canon 5D and Canon Rebel xTi(400D). The xTi/10-22mm zoom combination is a very tempting backpacking option, lighter than film and better in almost all aspects.
Backpacking Camera Gear List
Tripod required: three separate images captured at the scene and
later combined in Photoshop. Canon 17-40mm f/4L
Indian Henry's, Mt. Rainier NP
For three-season backpacking, I’ve chiseled my pack weight to 35 pounds for a 3-day trip: 19 pounds for pack, clothing, shelter, stove, etc.; 10 pounds for camera gear; 6 pounds for food. Here’s a typical backpacking camera list for the Canon 5D and Rebel xTi.
| Equipment |    Weight |
|
  5.8 oz. 16.8 oz. 25.0 oz.   5.0 oz.   1.5 oz.   2.0 oz.   1.8 oz.   1.7 oz.   1.5 oz.   2.0 oz.    .4 oz. 12.0 oz. 43.0 oz. 10.1 oz.   1.2 oz. 158.4 oz.   9.96 lb. |
|
  3.9 oz. 13.6 oz. 16.8 oz.   5.0 oz.   1.5 oz.   2.0 oz.   1.8 oz.   1.7 oz.    .4 oz. 12.0 oz. 43.0 oz. 10.1 oz.   1.2 oz. 129.8 oz.   8.11 lb. |
For the Canon 5D set, if I go with one lens — usually by leaving home the 70-200mm — I can also exclude the 67mm polarizer, and the sensor cleaning lens pens and blower since I won’t be changing lenses. Also, I can use a smaller camera bag instead of a fanny pack. In sum this cuts 2.82 lb. for a total camera gear weight of 7.14 lb. — not a bad compromise for the joy of making 80% of the shots I’d want to take.
The Canon 10.1MP Rebel xTi, or similars from Canon, Nikon, etc, is a more likely companion for most backpackers, and very attractive with combined pack weight about 1.7 lbs. less then the 5D set, much less cost, and, for the xTi, built-in sensor cleaning. The 1.6x mulitplier means the 10-85mm range for the two-lens set covers 16-135mm. Expect no discernable image quality loss compared to the 5D for sizes up to 11x14 at 100 ISO.
Gary
Also see FAQ for on-the-water advice.