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Pentax Stereo Adapter for SLRs

This is an adapter that attaches to the front of a regular SLR's normal lens. One then takes photographs on slide film at f/5.6 to f/8 and the result are standard 2x2 slides except that the image has two vertical striped sub-images, one for left and one for right.

One then puts that slide into the viewer (both viewer and adapter are in the first photo above) and one sees in 3D! Yes, it uses (front surfaced) mirrors!

The advantages of using this device is that it provides one with a stereo camera that is through-the-lens viewing and has automatic TTL exposure (assuming an averaging mode is being used in the camera). This method also provides one with very high shutter speeds when used with high speed film on sunny days. This device also allows use of standard slide processing available most anywhere. It does not require special stereo processing nor does it require any special mounting or mounts. Just take slide photos and put the results into the viewer. Using this format, one also can switch between 3D and 2D however many times one wants to mid-roll.

The disadvantages of using this device also are several. First, the quality isn't as good as some other methods because the images are narrow and tall (usually there is a somewhat fuzzy black stripe vertically between the two images which isn't visible in the viewer). Second, the viewer is at best "okay", not the excellent viewer that's available in other 3D formats. Third, although 3D projection is possible in this format, it isn't terribly good or practical that I've seen). Forth, one is constrained to f/5.6 or f/8 while one might really rather use f/16 or f/22 for one's photography.

Although the Pentax version of adapter is the highest quality adapter of its type that I know of, there are certain practical use limitations that are common to all mirror-based 3D camera adapters such as this one:

  • Use only on "normal" (fifty-ish mm f.l.) lenses.
  • Use only on lenses who's front filter ring (that it attaches to) does NOT rotate when the lens is focused.
  • Preferably use an SLR who's shutter curtain moves vertically. This provides better time-synchronization matching between the left and right images.
  • Use only f/5.6 or f/8 lens opening so a camera with manual f/stops or equivalent automatic mode needs to be used.

The Pentax stereo adapter pictured above was what I started 3D photography with in the very late 1970s' (used on various Pentax SLR's over the years, last one being a Pentax SF-1). It also was used by a friend to take photos at my wedding, and those stereo images are more prized by us than the ones taken by the professional wedding photographer! Makes one think "I'm there" rather than making one think "I remember being there".

To summarize, the adapter technically "isn't the greatest", but it likely is the easiest.

Copyright ©1999 by Michael Kersenbrock