Stereo cameras produce two side-by-side images, one for the
right eye and one for the left. Computers display color by mixing
varying amounts of three primary colors: red, green, and blue.
The information for each color is called a channel. To make an
anaglyph, we place the left eye image into the red channel and
the right eye image into the green and blue channels. (The lens
for the right eye appears blue but it actually is both green and
blue.) With the two views now in separate channels, the vertical
and horizontal registration of the two images is carefully adjusted.
Moving the red channel horizontally relative to the others brings
the entire stereo image forward or backward in space.
The AMNH Digital Library Project scanned the original glass
plate negatives at high resolution, then called on 3-D imagery
expert Gerald Marks to assemble the scans into anaglyph form and
prepare them for the web. Anaglyph is one of the oldest ways to
display 3-D, yet it has proved to be beautifully suited to the
Web and digital multimedia. These glass plate images may have
been projected using the anaglyph technique soon after they were
returned to the museum almost 100 years ago.
We've selected samples from the approximately 1500 stereoscopic
negatives produced by Herbert Lang during his six-year stay in
the African Congo. The images presented demonstrate Lang's interest
in the daily life and activities of the Congo peoples. These images
were also selected for their ability to demonstrate the beauty
and utility of the 3-D effect.
For further readings and sites on stereo photography, consult
the following links:
PullTime 3-D Laboratories
New York Stereoscopic Society
and background of Stereo Photography from the New York Public
Library, by Julia Van Haaften.
National Stereoscopic Association
from the California Museum of Photography
View the Stereographic Gallery
You can receive a free pair of the red/blue
glasses by sending your name, address to: email@example.com
(While you are at it, please tell us what you think of the 3-D
site and the Congo Expedition web site in general. We appreciate
any and all feedback.)
In order to experience the images presented here in three dimensions
one must use a viewing device to provide separate images to each
of your eyes. Anaglyph is a technique enable enabling 3-D imagery
through the use of simple red/blue glasses. You can receive a
free pair of these glasses by writing to us through the
email address above.