Home
Back to Articles

Information for Preparation

A SIMPLE METHOD FOR STEREO PHOTOGRAPHY FOR FOSSIL SPECIMENS

Bill Mueller
Texas Tech

There are a number of books and websites that provide methodology, formulas, and directions for creating stereo photographs. These techniques are not convenient for most paleontologists who are visiting a facility's collections because of equipment requirements. Still, being able to make quick and simple stereo photographs during such a visit can be helpful in later research. Stereo photographs are, very simply, a pair of photographs made from the viewpoint of the left and right eye that produce a three dimensional image. Optimally, when printed on hardcopy the images' axes should be 60-65 mm apart (approximately the same width of the eyes. I frequently view my stereopairs on the computer screen. The following method is one I have used with satisfactory results. It is not perfect; however, it is simple and easy for anyone to utilize when visiting collections. I have used this technique to photograph tiny specimens to phytosaur skulls over a meter long with good results.

Materials needed for photographing small elements (~30 mm):


Copy stand or tripod (most collections have a copystand available).

Lightsource(s)

An 8"X12" photographic grey card, piece of mat board, or any thin, flat, rigid, material. The grey card is also used for metering the proper exposure.

Two cylinders for axes (inexpensive ink pens work for small objects).

A small weight (Almost anything that will not roll on an inclined angle. I usually use my pocket calculator since I usually have it in my notebook.)

Scotch tape.

A compass to measure the angle of rotation (my Brunton works well).

For the back ground you can use white or black paper, the grey card itself, or cloth of the desired color.

A small quantity of Fimo or Sculpy clay (same color as the background so it blends in). Used to hold the artifact in the correct orientation.

I typically use a Canon 100mm macro lens and use the self-timer to prevent vibrating the camera.

Method


In the final stereophotograph, the axes of the photographs will be vertical and must be perfectly aligned. This is easily done on the computer, more difficult in the darkroom. Standard lighting of an artifact is from the upper left; however, this may not always accent to topography you want to illustrate.
The size of the artifact, distance from the camera, and lens guide you on how much rotation is needed for accurate stereo images. Over rotation will exagerate the topography and under rotation will flatten the topography of the artifact. The procedure can be used with digital or film SLR cameras. With the "point and shoot" digital cameras you have to adjust for paralax and that can create some extra work to align the axes. A 50 mm lens is a "normal" lens. The following calculations are made for a normal lens. If you are using a 100mm lens, then the amount of rotation needed would be half of that for a 50 mm lens. The more magnification, the less rotation is required.
If your lens is 300mm (1 ft.) from the specimen, you need an angle of rotation of about 12 degrees. If your lens is 600mm (2 ft) then you need about 6 degrees of rotation. At 1200mm (4ft) (about where you would be if using a tripod and the artifact was on the floor) you require only about 1.5 degrees of rotation. Typically, the larger your specimen, the larger the platform that it rests on, and the further the lens is from the artifact.
With practice you will recognize through the viewfinder if the specimen is over or under rotating and adjust accordingly. Rotating less is easiest because all you have to do is put a bit of clay underneath the edge of the support to stop it from rotating as far. Rotating more may require using a larger "axis" than the pen.
Always use the scale in the photograph of the "flat image". This way the image can be used by itself or in the stereophotograph. If you leave the scale on the tilted image, mask or cut it out on the computer.

Continue to take pictures.

Copyright © 2007, Bill Mueller