Re: Twin rig

[P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>Date: Wed, 15 Oct 1997 19:20:19 -0500
>From: P3D Brenda Nowlan  <bknowlan@xxxxxxxxx>
>Subject: Twin rig

>I am interested in the differences/pros/cons of the the Canon Rebel vs.
>the Minolta X-700 rigged for stereo.  I recently read this on P3D:

>Gecko wrote:

>>>I'm looking to purchase two Canon Rebel G SRL's for use as a twin 3D
>>>camera.

>>>Does anyone have comments regarding their use as a twin setup?

>>I've recently tried my twin camera rig consisting on 2 Canon EOS 500N
>>(the european version of the Rebel G) mounted on a slide bar purchased
>>to Reel 3-D with very good results, Firing both cameras together was
>>accomplished by means of two solded remote cables (from Canon). The
>>500Ns are one of the lightest SRLs available, they come with a useful
>>zoom (in my case a 28-80mm) and offer a full array of manual and auto
>>modes. There's even a program setting called  A-Deep to maximize depth
>>of field: The auto focus detects the nearest and farthest objects in the
>>scene and tries to keep them both in focus...

>So, what does the Minolta X-700 have to offer?  
>Also, does anyone know other sources for slide bars for comparison?

It looks like there's not much difference in price these days. For me, the
X-700 has a tremendous advantage - I already have a pair. :-)

The X-700 has manual focus, Program mode (automatic aperture and shutter
selection), aperture priority autoexposure but no shutter priority (I would
consider Program and aperture priority more useful than shutter priority
for twin-camera stereo), and full manual mode. The exposure indication is
by a set of numbers that light up to indicate suggested or chosen shutter
speed. Through-the-lens (TTL) flash exposure is possible, which is convenient
for applications such as macro photography. One very interesting feature of
the autoexposure modes is that while an exposure estimate is made when the
shutter button is pressed, a second reading is taken automatically after
the aperture stops down, and the shutter speed is adjusted if necessary.
When using exotic equipment such as extenders and close-up filter-type lenses,
the second reading compensates for all sorts of phenomena that would tend
to cause the wrong exposure. The X-700 also has a very convenient depth of
field preview - push a button and the aperture stops down, release it and
the aperture opens up again. Some cameras have control sequences you have to
avoid when using stopped down mode to prevent damage to the camera.

The X-700 has no "menu" settings - it's covered with buttons and levers
and knobs with the numbers written on them (aperture, shutter speed, etc.).
When you're trying to control two cameras at once, having all the settings
visible at the same time makes it a little easier to make sure they're both
set properly.

My X-700s work very nicely most of the time. I can judge the synchronization
by listening to the shutter clicks of the two cameras. I built my own
electrical shutter release cables rather than buying the Minolta models -
occasionally the inner contacts slip and need to be adjusted. Use the
same kind of batteries in both cameras, and replace them at the same time
in both cameras. (The X-700s use cheap batteries, and they last a very long
time - an advantage over some modern cameras. They're probably good for over
a thousand shots, though I usually try to replace them every few hundred.)
I recently took several rolls of photos of rushing water in a mountain stream,
and most of them appear to be "perfectly" synchronized.

I built my own stereo camera bar, very quickly before a vacation trip years
ago - it's not a perfect design, but it has worked too well to justify the
effort to redesign it or the expense of buying one. I can keep the cameras
attached all the time (except for changing batteries), but I can also very
quickly install or remove the cameras (for carrying on an airplane, or for
2D or macro use). The bar is just slightly longer than the combined widths
of the two cameras, and the whole assembly will fit in a small cloth camera
bag. I designed it for use on a tripod, but quickly discovered that it's
very easy to use handheld, and I can attach one neckstrap to the two
cameras and carry the assembly around my neck.

If I ever make it to the Potomac Stereo Club, perhaps I can bring it.

The downside of the X-700 is that it's a very old technology - they seem to
still be making them, but the day may come when it's hard to find new lenses
and other accessories. I tend to be cautious about autofocus stereo, but
some people have reported good results, and the X-700 doesn't offer that.
I don't have any idea of comparative weight of the two systems (I'm also
guessing at the kind of controls the EOS has).

I don't get a strong impression that either system is a clear "best choice"
to purchase for a new twin stereo camera. I'm very fond of the Canon A-1
(though it doesn't have an electrical cable release), but I've never used a
more modern Canon camera, so I don't know much about them. When I was
pricing cameras for my twin rig, the Canons with the features I needed were
much more expensive.

John R


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