The Bruce Gordon
's BLT is the "ideal" in terms of gearing and tire clearance. In other words, aim for low gearing. Pricewise, if it fits your budget and if you are not too tall (the BLT stops at 56 cm (oblique tube) which is equivalent to a 58-59 cm hz tube), go for it. Everyone on the Touring and I-bob lists who owns a Bruce Gordon loves it.
Other possibilities are the Trek 520, Cannondale T series and a few others are praised, notably a tourer by Fuji, the Bianchi Volpe (a little lighter). If you want to shop in Canada, Urbane Cyclist
in downtown Toronto offers a very interesting tourer, the Urbanite Touring
On the plus side, the Urbanite Touring is configured the way you want.
Another popular setup is a cyclocross bike such as the Surley Crosscheck. I find, however, that the rear stays are a little bit too short to allow hell clearance around many panniers.
Basically, any frame with rather beefy rear triangle, low gears, 45-cm chainstays and room for 700x35-40 tires would fit. If you get the Trek 520, for example, you could use two sets of tires. For rugged trails, you could mount cyclocross tires (knobbies) 700x32 or 700x35 in front and even 700x40 on the rear wheel for relatively good traction in sand and a relatively smooth ride on rocks. Then for on-pavement tours and commuting, you could mount 700x32 slicks.
Look at Sheldon Brown's Gear chart
. Many tourers think that a touring bike should have gearing between 20" and 100". I have a Trek 520 with a MTB drivetrain (swap at purchase time): 44-34-22 with a 12-32 cassette. Essentially, the low gear would allow you to do the gravel roads and trails, including their hills, without problems and the 100 gear-inch high still allows you to pedal up to 40 km/h.
I prefer curved (road) bars whcih, on the long run, offer more positions and keel the wrist in a straight line. I put my bars much higher than roadies, as the top of the bar is level with the saddle. Just make sure the bike shop doesn't cut the fork too short too soon!
Racks or Trailer; 1 or 2 wheels?
There are two possibilities. I think you need a rear rack anyway. If you think in terms of panniers, then also get a front rack (Lowrider preferably). Good panniers include the Arkel
's Touring series. You might attach your tripod on top of your rack with bungee straps or you might adapt (or have Arkel adapt) the long pocket on the right side of the GT-54 to fit the tripod.
Trailers, especially the 2-wheel variety, store more and would be essential if you do large-format photography. Some people prefer them, but they are a bit more bulky to handle, I think.