If you go with aluminum you have to consider the alloy being used. 6061 is a non-bendable, more brittle alloy that is primarily used for structural applications. It can flex some but will not hold a bend and at a specific load point it will break. 6061 machines better, cuts cleaner, holds threads better but is more difficult to machine then 3003.
3003 is considered an aluminum alloy for forming and thus can be bent at angles in a metal break machine, worked on an english wheel and bead rolled. it is much easier to machine if using hand tools such as a dremel style cutter and hand files.
The problem with 3003 is that it is not nearly as structuraly stiff as 6061, and thus for example a 2" wide .125 piece of 3003 bent at a 90degree angle will not have the rigidity of 2 peices of .125 6061 welded and reinforced to make the same angle. However rolling a bead will substaintially add to stiffness.
6061 can be heat treated and annealed, which provides the ability for forming but it will loose a certain amount of strength at the point of any bend.
There are more exotic alloys with different characteristics. 5052/51, 7071, 3035, but these are more expensive and not as common and really provide no advantages for simple applications such as a camera.
Ideally for something small like 4x5 or 5x7 you could use stainless steel. But you would really want a machine shop to slit it to size, and machine holes and slots. Proabably about a $100 to $125 job.
If you are working with small dimensions, for say a 4x5 (6" between uprights and say 8" uprights on each side) and choose aluminum, you should be able to find everything you need at an Ace, True Value or Home Depot. They all have a selection of aluminum flat, angle and channel in thcknesses of .063 and .125 and usually from 1/2 inch widths on single sides up to 2". The angle and channel are usually 6061 and the flat is 3003 or similar.
With aluminum, drill and cut any holes or slots before bending. If you are making a simple slot for say the shift and swing on a front standard, mark a center line, center punch a series of holes, drill and finish the slot with some sharp files or a dremel type tool. A machine shop will cut a slot for you but will charge you at least $50-$60 or what ever their hour minimum is.
I could provide you with more specific suggestions if I knew the demensions of the pieces you need to make.