Single-Lens Anaglyph Aperture Tool

Would you like to be able to capture "3D" images using your current film or digital, still or movie, camera? Got $1? The anaperture CGI is an interactive WWW tool for creation of the special dual-aperture discs proposed for single-lens anaglyph capture.

An anaglyph is a type of stereo image in which the left and right sides are encoded in a single image by assigning approximately non-overlapping colors to each side. Although many color assignments can be used, the most common are red/cyan and green/magenta. To see depth, you use viewing glasses that have color filters causing each eye to see only the colors assigned to that side's view.

Normally, two separate images are captured and then processed together to form the anaglyph. Instead, we can directly capture the image as an anaglyph by using filters cut from cardboard-frame viewing glasses of the same colors used for viewing. This will wreck a pair of glasses, but they cost no more than $1. Alternatively, you can use photographic or stage lighting gel filters; stage lighting gel samples are cheap and generally come with graphs of the measured spectral transmission.

The two colors normally would be placed in front of two separate lenses, however, it suffices to create two optical paths within a single lens. This is done by a type of dual Waterhouse Stop -- a fancy name for a piece of dark paper or cardboard with two holes in it. If the holes are sized and placed correctly, and the appropriate filter is placed over each, capturing an anaglyph image is as simple as placing this new stop in front of the lens and pressing the shutter button.

The hole size and placement are critical, and depend on some properties of the lens. Note that many lenses have inaccurate markings (e.g., marked as f/3.5 might really be f/3.8) and zoom lenses may need multiple stops due to having different properties at different focal lengths. The anaperture tool accepts a few key parameters, computes the ideal stop design, and generates a Scalable Vector Graphic (SVG) image of the stop for printing. Laser or inkjet print the stop, tape color filters over the holes, cut it out, stick it in front of your lens, and capture some anaglyphs!


The SVG image at 100DPI is:

A link to recreate the SVG image at the reference 600DPI is:

http://super.ece.engr.uky.edu:8088/cgi-bin/anaperture.cgi?t=49.0&l=50.0&f=1.4&s=8.0&b=29.2&o=0&d=600

Parameters for the above are:

Lens filter thread is 49.0mm, pattern reduced to 48.5mm to fit inside thread
Lens focal length is 50.0mm
Widest f/number of lens is f/1.4, or a diameter of 35.7mm (1.4in)
Generated f/stop is f/8.0, or a diameter of 6.2mm (0.2in)
Stereo baseline is 29.2mm (1.2in), with an optimal near subject distance around 0.88 meters (2.9 feet)

Note that the center is marked with a cross to aid in alignment and there are two black tones; the lighter one is used to indicate the area beyond the widest aperture. Having an aperture stop that exposes part of the lighter circle risks serious vignetting problems. This design tool currently assumes a positioning error of 0.25mm, and thus avoids critical region overlaps by at least this amount. In general, this tool attempts to find the closest viable parameters if the ones requested are infeasible.


Make a new stop as specified by:

Lens filter thread is marked mm
Lens focal length is mm
Widest f/number of lens is f/
Desired f/stop is f/; enter 0 to automatically maximize
Desired stereo baseline is ; enter 0 to automatically set
Desired SVG inline DPI is ; set this to match your screen resolution

Anaperture was created by Prof. Hank Dietz on August 17, 2010 as a service to the community. We have tried to make it correct and useful, but you use it at your own risk.


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