Q. Why do some cards have a yellow background while most are in blue?
A. All stereo views require two images, one for each eye. In some cases one of the images is not available, either the side was lost, or destroyed. Sometimes the image was not taken with a stereo camera and could not have been produced as a stereograph. To allow these “orphan” images to regain their place as stereo cards, we utilize 3D simulation software to recreate (as close as possible) the missing side. All of these cards are shown in yellow and a note in the text description of the image clearly states that 3D simulation software was used.
If the image is in blue, then both sides exist at the Library Of Congress, and both sides were restored and colored. While the simulation software is good, it is not a replacement for the depth of an image when both sides are available. If the Library of Congress discovers and posts a side that is missing we will replace the yellow card with a completed blue card.
To see an example of one of these, click here.