The Loreo LIAC 3d attachment as a 3d macro device.
By Donald E. Simanek.
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The Loreo "Lens in a Cap" (LIAC) beam splitter 3d attachements "out of the box" will only focus at distances greater than 1 meter (approximately 39 inches). In late 2008 Loreo released the Loreo macro adapter with smaller stereo base, capable of focusing from 9 inches to 32 inches. Back in the 1950s, when 3d film cameras proliferated, close up lens sets were available. These were specific to the particular brand of camera and not only did they allow for shorter distance from camera to subject, they were also prismatic, to cause convergence of the stereo axes. Those of us who were do-it-yourselfers, and cheap as well, accomplished the same thing with large lenses of diameter great enough for a single lens to cover both stereo lenses at once (about 3 or 4 inches diameter). This provided both decreased working distance and axial convergence. I happen to still have a 4 inch diameter lens large enough to cover the entire front of the Loreo attachment, duplicating this method exactly. The result isn't pretty, as seen below.
The convergence of the chief rays introduces keystone geometric distortion and also greatly exaggerates the depth. This might be fun for "comic" effects, but not for much else.
Obviously the digital camera's autofocus does not function with the Loreo attachments, but its auto-exposure does, even for flash exposures. The three manual settings are sufficient for most ordinary photos. Setting the camera on "aperture priority" and autoexposure selects the shutter speed. This picture should have been taken with bounce flash instead of direct flash, and a plain background would have been better.
There is another way to shorten the working distance of the Loreo to about 1 meter or less without severe spatial distortion.
How was this done? A supplementary lens of 1.37 diopter was placed at the back of the adapter with two pieces of poster tape. [Nothing special about that value, I just happened to have one handy.] With my Pentax 1sDS camera this does not interfere with the camera mirror's motion, but you should check your camera's design carefully and make some measurements before attempting this.
The subject distance in the picture above is about 1 meter, which just about conforms to the 1/30 rule for axial separation of 2 inches. Since the horizontal field angle of view is still about half normal, the picture does not display excessively exaggerated depth. The pictures must be cropped in width more than usual, using StereoPhotoMaker, or similar, software. Anticipate this when framing the picture. You will crop away as much as half the picture area.
This rabbit was photographed in a pet shop. It illustrates that the modified Loreo LIAC could be useful for this size subject.
This flower arrangement was photographed at a garden show.
This Christmas tree ornament sparkles in the light of the on-camera flash, just as it would appear to the eye. The reflecting facets of the ornament can reflect light directionally, so some are seen brightly by one eye but not the other. The crystaline surface of snow in sunlight shows the same effect in stereo.
Back to the garden, this picture of a bumblebee again shows the avantage of this easy-to use modified beam splitter adapter for macro photography of small wildlife. This was cropped quite a bit.
So, if you paid $110 for a Loreo stereo adapter and were wondering what useful task you might put it to, here's the answer. The modification is non-destructive and it won't cost much, either.
Donald E. Simanek
All pictures on this page not otherwise credited are © 2008 by Donald E. Simanek.
Stereos for cross-eyed viewing in 3d Gallery One.
Digital stereo photography tricks and effects.