Canon Rebel Twin Rig
by Jim Norman
Below is Jim Norman's set-up on making a Canon twin rig. Please click
on illustrations for a larger view of the images..
I hope you'll forgive this rather long post, but I've been asked by a few
people for details about my Canon Rebel twin rig. In the belief that some of
what I've done is equally applicable to other brands of SLRs, here's what I've
been sending them individually:
H
ere's
how I've got my Rebel X rig set up: The cameras are mounted vertically, so that
their offset tripod sockets are directly opposite each other. Each camera is
attached to a bracket that I made out of half-inch thick wood. The part of the
wooden bar where the quarter-inch bolts go into the tripod sockets is cut out
and covered on both sides with 1/16 inch aluminum, allowing access to the heads
of the bolts with an offset wrench for camera removal and attachment. The reason
I mounted them vertically is to maintain a relatively small distance between the
lenses -- in this case about 75 mm center-to-center.
In
order to fire the cameras simultaneously, I bought two Canon remote shutter
release cables, which are simple electrical cords that plug into the side of the
body and are controlled by three-position buttons. First position is off,
halfway down activates the focusing and exposure metering, and all the way down
fires the camera. I snipped the button end off the two cords, making sure to
leave enough wire attached to the button ends, and carefully spliced the camera
ends of the cords into a single button. The other button went into my junk box
for future use on some other project. Pressing one button causes both cameras to
meter, focus, and fire at the same time.
I could have made life simpler by choosing to go with 50 mm prime lenses for
both cameras, but I was intrigued by the flexibility of zoom lenses, running
from 35 to 80 mm. Problem was, how to link the
zooms so that rotating the barrel of one also drives the other. I found a 3/8
inch wide toothed industrial rubber belt in a junk shop on Canal Street in New
York, and cut that into several lengths. I turned it inside out, so the teeth
were on the outside, and glued a piece around the circumference of the zoom ring
on each lens.
Then, I found a couple of nylon idler wheels at the same junk shop. The
wheels ride 
on
a ball-bearing hub, with a center hole of exactly 1/4 inch. I glued some of the
same belting material around the circumference of each idler wheel, then
positioned the wheels so that they were in contact with the belting on the
lenses. I attached the wheels to the wooden frame between the two cameras with a
1/4 inch bolts. In theory, I figured, if I set both zooms at one extreme or the
other, then turned one, the other would follow exactly along because of the
meshing of my home-made "gears." But the problem was that every once
in a while the contraption would jump a tooth as a result of being knocked
around (I'm a pretty physical photographer and tend to get into knocking around
situations a lot), and the zooms would go out of synch. I solved that problem by
buying a piece of elastic fabric band from the local sewing store, and
stretching it in a continuous band around both lens barrels so that the tension
kept the lenses in constant contact with the idler wheels. The elastic material
is kind of lacey, and looks like it came off something you might find in a
ladies' lingerie department, but at least it's black, and more to the point, it
works!
Next step: how to use flash with this setup? The wooden bar that runs
vertically between the two cameras has a wooden T-top epoxied across the top of
it. Imagine a letter T, with the two cameras mounted to the vertical. I put a
flash shoe on one side of the top
surface of the T (not a hot shoe, just a bracket that I cannibalized off a cheap
flash holder). I put a Vivitar 283 into that shoe. The Vivitar has a plug-out
sensor unit in the middle of the front of it. There's an available Vivitar
"remote sensor cord" which fits into the hot shoe of either camera at
one end, and into the plug-out sensor receptacle in the flash head at the other
end. Most photographers use it for off-camera flash. You use it by unplugging
the sensor unit from the flash and plugging it into the end of the cord that's
mounted on the camera hot shoe, then the flash end of the cord plugs into the
place where you took the sensor from.
Assuming
the cameras are in proper operating order, and they meet factory specs relating
to shutter firing, then pressing the single button will fire both cameras at the
same time, and will also fire the flash that's hooked up to one of the two
cameras. Because the cameras fire at the same time, the flash exposure will be
proper for both cameras.
For flash work, I set the cameras to the manual exposure mode, but leave
autofocus on. I decide what aperture I want (usually f 11) and set the flash to
expose properly at that aperture for the speed of whatever film I'm using
(usually 100 ASA slide film or 200 ASA print film). I set the shutter speed to
the proper synch speed or slower. If memory serves, that's 1/90 sec in the Rebel
line, but I don't remember because I ALWAYS choose a lower speed in other to get
a little ambient room light to register on the film. Generally, I find I'm
shooting with flash at 1/15 or 1/30 sec shutter speed, sometimes slower.
For ordinary outdoor non flash exposures, I set the cameras to aperture
priority, usually at f 11, and let the cameras decide on the proper exposure.
The only drawback to all of this is that it locks you into full-frame
vertical format. That's great for producing Holmes style side-by-side print view
cards, but I haven't found anyone who makes a full frame vertical stereo slide
mount. As a result, if I want to project slides shot from this rig, I have to
either use two synched carousel type projectors, or I have to jury-rig a spacer
between the two mounted slides so they will fit into the rear channel of a TDC
slide changer.
One other thing: remember that T-top? I glued an identical piece of wood
across the bottom of the vertical bar. When I'm shooting hand-held (almost
always) that gives me something to hang onto, to help stabilize the whole setup.
I've also got a 1/4 inch T-nut embedded in the bottom, to serve as a tripod
socket.
