Stereo vision

Stereo vision is the equivalent of stereo audio, where two channels are recorded and played back back through a pair of speakers or headphones. In stereo photography, two photos are taken from eye distance apart and viewed with a special viewer. It's also possible to train your eyes to view them without a viewer.

We can view the two images using a viewer. The two lenses magnify and separate the left and right images so the left eye sees only the left image and the right eye sees only the right image. Our brain then fuses the two together, computing volume and distance information to give an amazing sense of depth and hyperreality.

Taking digital stereo photographs
First the bad news: At present there is no dedicated digital stereo camera avaialble. The good news is that you can take stereo photos of static subjects using any camera digital or film by taking a pair of photographs from eye distance - approximately 6cm or 2.25 inches apart, or greater. For the photo of the Angel of the North I took one photo, then moved about a metre to the right for the second.

A slide bracket is available which allows you to shift the camera from one position to the other. You can take only static subjects using this method. I've tried using a pair of digital cameras, but found it difficult to get the cameras to fire at precisely the same moment and to get colour and zoom settings to match.

The Loreo beam splitter can be used with SLR cameras, but it is only suitable for full frame sensors.

Image capture tips
The two photos have to be exactly vertical and exactly at the same height in relation to each other. Remember our eyes are level and we see both images horizontally. Even the smallest variation in height or angle will make the images difficult, even painful to view. Only static subjects are suitable for the 'shift camera' method. Rooms, rock formations, statues, sculptures, buildings are fine, but not trees, people, water or anything that moves. For that you require a stereo film camera. There is no digital stereo camera commercially available at present! Please inform me if you know of one.

Viewing
The best way to view a stereo photo is to make a 6x4 print and place it in a stereo viewer. More advanced viewing options include shutter glasses at around £60 and the amazing SeeReal display which requires no glasses and costs several thousand pounds.

Stereo imaging can also be used to add an extra dimension to computer games. You can use it to bring added realism to Microsoft Flight Simulator. You can also view the Harry Potter movies in stereo on your computer. Stereoscopy is used by molecular scientists, medical researchers, in aerial photography and on the Mars landers. I hope that soon it will come back into widespread use for creative photography. But until we have a usable digital stereo camera, and a cheap and hassle-free viewing method, that won't happen.

By Aidan O'Rourke