Re: Stereo with your SLR!!!

[P3D Larry Berlin <lberlin@xxxxxxxxx>]

>Dr. George A. Themelis writes:
>......
>- Portraits?  Yes, I have seen a few portraits from single cameras.  
>  You must have a cooperative subject (my hyperkinetic children to 
>  not apply) but it can be done with a small base too!

That's a great list of 3D things to do with a single SLR camera! I recently
experimented with a technique that makes it possible to easily shoot moving
objects, such as kids, in stereo with a single camera. I used it for a self
portrait in 3D experimentally and it worked well. I'm using the results on
my website in a number of ways. One image is posted now at
http://www.sonic.net./~lberlin/graphics.html, and more will follow. This is
not intended as a high res. portrait. I will be using the method again under
better conditions.

The basic trick is to use two rectangular mirrors next to each other and
angled slightly so that from a close distance you can see two views of the
subject by looking into the side by side mirrors. I intended the results for
my web page and didn't have a very large set of mirrors available, so the
resulting image in my experiment was rather small. I used a dark sheet
behind me so that I could easily separate usable parts of the image from the
rest of the picture. I placed the camera on a tripod and located it just
above and behind me aimed at the two mirrors. I then reached up behind to
the camera and while looking into the mirrors at the camera, clicked the
shutter release. 

The resulting view is parallel viewable on the prints. It is similar to the
results from a *beamsplitter* (Maybe we just like the name?) but in this
case the mirrors aren't attached to the camera. Since they are used at a
distance and the angle of use is close to perpendicular, ordinary back
surfaced mirrors won't cause much distortion. I plan to get a hinge for a
pair of matched mirrors set up so that I can use it more often and without
all the shuffling around and bracing of mirrors that went into this experiment.

My experiment was hyper-stereo because the mirrors had frames (couldn't get
them close together) and were narrow so I had to use a larger angle than I
wanted. With the right set up one could adjust for a range of views to
satisfy both the ortho and the stretch person... 

There are limits of geometry imposed by this use of mirrors, but it's easy
to use for where it does work. Using mirrors, everyone with a camera could
have their own 3D portrait on the web! It would be easy to do with the
simple digital cameras being used on computers now. Since it's a single shot
with one camera, movement of the subject, or wind blowing doesn't mess it up
for you!

I don't recall ever hearing about such a method for stereo photography but
it's so basic it must have been tried at some point. Anyone hear of it before?

Larry Berlin

Email: lberlin@xxxxxxxxx
http://www.sonic.net/~lberlin/


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