It’s difficult to avoid 3D these days. Movies at your local multiplex are in 3D, television in 3D is the latest innovation and Fuji has introduced the first digital 3D camera. But there’s nothing new about three dimensional, or stereo, photography. Stereo cameras have been around for years and are still usable and very effective when you combine their old-time shooting methods with modern digital techniques.
The reason we see in three dimensions is because each eye sees a slightly different view. The brain takes those two views, combines them and gives us the illusion of depth. A stereo camera has two lenses, shooting two pictures at a time. When the pictures are viewed so that the left eye sees only the one taken with the left lens and the right eye sees only the one from the right lens, the brain does its magic and you see a single image in three dimensions.
Finding and Using a Stereo Camera
Early stereo cameras took glass plates. Later, they took roll film. But during a resurgence of interest in the 1950s, many were made for 35mm. These are the best to use today. You can find them at classic camera shows, from specialist dealers, in thrift stores, at estate sales and on eBay.
The one used for this article was an American Stereo Realist, made by David White & Co. Here are its specifications: two lenses to shoot pictures and a third between them to reflect its image to the viewfinder; apertures between f/22 and f/3.5, shutter speeds from 1 second to 1/150 second, and focusing from 2 1/2 feet to infinity. The knob that focuses the lenses is surrounded by a depth of field scale, and its importance we’ll come to soon. There’s no automatic exposure, but that setting was measured with a Nikon D80 digital SLR and set manually on the Realist.
Stereo pictures are all about depth. A picture where everything is in the far distance, or in which the subject is on a single flat plane, does not make good 3D. So the subject is best considered as a series of layers, getting some object strongly in the foreground, including detail in the middle distance and letting the far distance take care of itself. Subjects like bridges, long roads or railway lines receding into the distance make good stereo pictures.
A deep depth of field is important to keep everything sharp. Depth of field is the area of acceptable sharpness in front of and behind the point where the lens is focused, and it increases as apertures get smaller. So stereo pictures should be shot at the smallest practical aperture with the focus set at the lens’ hyperfocal distance.
The easy way to do that with the Realist was to set the infinity mark on the focusing knob against f/16 on the depth of field scale, so that every picture taken at f/16 was in focus from just under five feet to infinity. Shooting in sunny conditions using ISO 200 film, the Realist’s top shutter speed of 1/150 second made an ideal match for the small aperture.
Processing and Scanning
Film from a stereo camera can be handled by most processing outlets, but tell them to develop only. Do not have them print or cut the film. The resulting negatives are unlikely to be the standard 24 x 36mm format. Stereo images are more likely to be square 24 x 24mm images.
Different stereo cameras handle the spacing of the picture pairs in different ways. The Realist does it by shooting a pair of pictures with space between that’s the equivalent of two frames. When the film is wound, the next pair of pictures is exposed beside the first two, leaving a space of one more frame to be filled when the next pair is shot. In this way matching pictures appear three frames apart.
The next task is to scan the negatives. You can do this with any modern scanner that handles film. Set it to scan negative film, not positive, and the scanner’s software turns negative images into positives.
You now need to differentiate between the right- hand and left-hand images. Assuming the film is wound left to right through the camera, look at the frame numbers in the film rebate, and the image with the lower number of the pair is the right-hand one. The Realist has an aid in the form of a tiny notch at the film plane, in the bottom of the right image area, which registers on the film at the top of the right-hand picture. (Don’t forget that because lenses record their images upside down, viewing a negative strip in the conventional way means that the right-hand image is on the left.)
Scan each individual image at a high resolution because you will be later viewing them in a viewer that considerably magnifies the pictures. For that reason 35mm images are best scanned at 4000dpi.
Finding and Using a Viewer
To view the pictures, you need a stereo viewer, which can be found in the same places as the cameras. Many viewers of the past were made for transparencies, with the viewer held to the light to see the pictures. Avoid these and go for a viewer that uses prints. Look for one made by a company called Vistascreen. They were cheap and simple when they were made; they’re even cheaper now, but they still work.
Next you need to make a template for your stereo pictures that is the right size and shape to fit the viewer. If your viewer came with some old stereo pictures, you can use one of those as the basis. Otherwise, measure the size of the place where the stereo pairs are to be slotted, plus the size and position of the places where each image is to be positioned. You can do this by trial and error by drawing two squares where you think the pictures should fall on a piece of paper, then viewing your results through the viewer’s twin lenses. When you find a place where the two squares meld into one, you’ve hit the spot.
Using Photoshop to Make a Stereo Pair
What follows are details of how to make a stereo pair using Photoshop, but you can use most image manipulation or drawing programs for similar results. With the rectangular marquee tool, draw a rectangle the size and shape of your stereo card, then put a 2pt border around it (edit > stroke, width 2px, color black). Repeat the action to draw squares within the rectangle the size and position of your stereo pictures). Turn the background into a layer (layer > new > layer from background). Then use the magic wand tool to highlight the center of each square and delete it.
Open the stereo pictures, then drag and drop them roughly into position onto your stereo card. Send each one to the back (layer > arrange > send to back). Take care to get the left and right pictures in the correct positions. Size each picture to fit the pre-drawn squares (edit > transform > scale). Flatten layers (layer > flatten image). Print on suitable photo paper.
The first time you look at a stereo image, you might not see it clearly. But give your eyes and brain a few seconds to adjust, and suddenly the picture pops into focus in all the glory of three dimensions. And once you’ve seen your pictures in stereo or 3D, you’re going to be hooked.
Product Resources: Cameras: Stereo Realist Stereo Camera, Nikon D80 Digital SLR for exposure measurement and non-stereo photography; Film: 35mm Color; Computer: Mac Pro OS 10.4; Software: Adobe Photoshop; Scanner: Epson Stylus S21; Paper: Epson Premium Glossy; Other: Vistascreen Viewer.