This is what im starting with, an explosion proof electrical box.
At 100 feet underwater, the water pressure will be 43PSI. The face of my housing will be subject to about 5000 lbs compression.
This is my TEMPORARY rigging. Im still waiting for my dome port, and flat port, but in the mean time I can get my rebel to fit if I use mirrors to reflect the lens and LCD.
You can see my magnetic reed switch inside the box, at the bottom. It seems to work really well, the camera will not take a picture until focus is achieved. I welded up a bolt on handle and at the top left you can see my orange o-ring seal.
This is how things will look when im done, the lens will stick through a port.
Waterproof push pins and control knobs can be installed in the flat 3/4" thick plexiglass cover. I used router to cut an o-ring groove 0.25" wide and 0.157" deep around the perimeter of the sealing surface. I'll be using a 3/16" (0.1875") diameter silicone o-ring with an ID of 13". I measured my o-ring groove and the equivalent ID is 13.05".
Closeup of the really smooth finish left behind by the router.
I freehanded the router, didn't want to spend all day on a setup.
I may install both a flat port and a domed port in my enclosure. The flat port for flash, and dome port for lens. I could also have one camera in each port so I can do macro and wide photography simultaneously. Holes will be cut in the aluminum, and the extension ports will be welded in.
A hole will be cut for the lens, and this port extension tube will be cut to length and welded in place.
This 8" dome twist locks to the port tube
I'll probably use my sacraficial digital rebel and kit lens for the first few dives =)
The volume of my housing was calculated to be about 675 cubic inches, or 2.9 gallons. For the housing to be neutrally boyant, it needs to weigh 24lbs (the weight of an equivalent volume of water). Currently the enclosure weighs 21 lbs, and the camera 3lbs, so Im very close to neutral boyancey.
My 580ex flash can be set to automatically fire slaves in ETTL mode, so I can have several flash units firing while still maintaining automatic exposure.