The Lens details of a series of images taken by Steve Cushing on mirrorless camera.

The Stitz Universal Stereo Adaptor Itzuki, Japan is the only known stereo adapter for telephoto lenses from 85 mm to 300 mm, It is a beam splitter lens and not just mirrors and has adjustment for distance relating to focal length and an aperture control. You can even add filters but need two of them! It can also be used for projection mine came with a 52mm adapter ring and case. It is a very rare beam splitter lens attachment.

Original Brochure Here

3D photos, much like 3D movies, have a reputation for being a bit of a fad. It falls in and out of fashion. Its popularity is on the rise again, but it’s not a modern phenomenon. It has been around for decades.

Humans see the world in 3D. Our eyes can detect height, width, and depth. Our brain processes the information from both of our eyes to give us stereopsis vision. It means we have depth perception and can judge distances. So often we arrive at a stunning landscape and start clicking away with the camera. Equally as often, the results disappoint us. This is because it's the 3D nature of the scene that makes it so stunning. And our photographs are only 2D. Therefore the "wow" factor is completely lost.

3D photography is a great way to add a little something extra to your photography. You can just take more than one image by moving the camera slightly to the left or right. But this only works when you have a stationary subject, because you need to take two photos in quick succession of the same scene with no other movement in the shot.

Try taking a 3D photo of your pet dog this way, and the chances are that Popcorn will have moved between shots!

This lens adapter means the two pictures are taken at exactly the same time so it does not suffer the same fate. Anything can be photographed.

Given that I did not want to buy a special camera for 3D there is another method that became popular in the 1970s and that was to use mirrors to capture the two images in a single frame. In simple terms it works lke this……

High precision mirrors capture the image from two slightly different perspectives. So after you snap a photo you see what looks like the same picture side by side. Combined, these pictures make a 3D picture (or video).

An astounding variety of 3d systems use first-surface mirrors or prisms to achieve stereo with a single-lens 2d camera. I avoid mirrors for general picture-taking, because of the difficulty of keeping the delicate silvered mirror surfaces clean. But they are interesting systems just the same.

Technically, optical systems that combine reflective surfaces and lenses are called catadioptric systems.

This design was actually patented as the "Stereophotoduplicon" in 1894 by Theodore Brown, and described in his book Stereoscopic Phenomena of Light and Sight, The Gutenberg Press, Ltd, London 1903.

This Lens

Many beam-splitter adapters have been marketed that use mirrors or prisms and a single lens and camera. Few are still sold. Their reflective surfaces were arranged as a combination of two periscopes. They put the L and R images side by side on the film frame or sensor, each image taller than wide.

This lens is the only true lens based upon this mirror method with aperture and focusing adjustment. The normal beamsplitters are all constructed for normal 35 mm cameras with lenses of a focal length of approx. 50 mm. Therefore they function only with lenses of that focal length. Another exception is the 65 mm attachment from Zeiss-Ikon. This lens has a focus and aperture adjustment making it fit any focal length even telephoto lenses.

I do also have a much cheaper and less collectable attachment that just has mirrors the Asahi Pentax Stereo Adapter and Viewer kit for 49mm f= 50/55

Lens In Use

When taking photos it is best if you choose something that has a lot of depth or at least is surrounded by other objects to increase the depth. Try to include items in front and behind the subject that may not be the centre of attention, but will help to increase the dramatic dimension.

One caveat applies to any mirror stereo system used with an autofocus camera. These cameras often use a supplementary red or infrared light to aid in determining the subject distance. This may not be properly beamed to the subject by the mirrors, resulting in poor focus. As I always use manual focus so that I have control over the total focus and bokeh of the image this is not an issue for me.

Perspective disparity is present in any single lens device that splits the camera film or sensor area into L and R eye images side by side. It results from the fact that the light rays that form each image strike the sensor unsymmetrically in the L and R images. The rays to a point in the center of the picture are tilted with respect to the sensor's normal. So a photo of a rectangular window would image as a non-rectangular trapezoid. The distortion is in the opposite sense on the L and R images. This is a small effect, and may be considered of no importance for pictorial subjects that have no straight lines and no important details near the corners of the picture.

The position and angle of the mirrors is important. It can affect (1) the virtual cameras' convergence, (2) the subject distance to the virtual lenses (both must be equal) and (3) the stereo interaxial.

The aperture control slides blinds across the lenses to help separate the two images and varying focal lengths and apertures.

Summary

This is a wonderful fun tool. I found the Asahi Pentax Stereo Adapter very limiting as it only suited certain lenses, certain objects, certain apertures and exactly the right subject and lighting. The Stitz is far more flexible and lots of fun to use.

See also Zeiss Stereotar HERE

For general information on lens design and lens elements go to the homepage HERE