Stereo

This command lets you prepare a pair of stereo images for 3-D viewing. The stereo transformation supports two types of viewing: using special glasses with red and cyan lenses (red on the left, cyan on the right) or using a viewer with prisms or mirrors that superimpose two adjacent images.

If you select the Red/Cyan method, the result image is generated with the left image displayed in red and the right image superimposed over it in cyan. This type of image is called an Anaglyph. For the Red/Cyan viewing method, both images should normally be black and white. If you select color images, they will be converted to black and white internally within the transformation in the process of computing the anaglyph. Or, you can select the Color Anaglyph method in which two color images are combined into a single stereo image for viewing with red/cyan glasses which attempts to retain much of the color information in the original scene. The success of the full color anaglyph method depends on the subject matter.

      Left Image              Right Image

   B&W Anaglyph         Color Anaglyph

In any case, to get the best result it may be necessary to adjust the horizontal and vertical offsets between the two images. It is usually easiest to do this by adjusting the sliders to get the images to line up while viewing the result through colored glasses or with some other 3D viewer.

Right Image

The image control lets you select the left and right images from a matched set of stereo photographs. By default, the input image is used as the left image and the right image is selected via the Right Image control. If you accidentally get them wrong, check the Swap Images box to swap the left and right images.

Horizontal and Vertical Offsets

These sliders let you adjust the offsets between the two images to get the best stereo effect. Changing the horizontal offset makes the 3D image appear closer or father away with respect to the image frame. Moving the horizontal offset slider to the right pushes the 3D image further away from you. In classical 3D photography, the image is supposed to appear to lie entirely behind the frame, but this is really just an arbitrary convention. It should only be necessary to adjust the vertical offset if the two images are vertically misaligned.

Method

This control lets you select the viewing method. Different stereo viewers require different arrangements of the two images.

B&W Anaglyph -- The result is designed to be viewed using red/cyan glasses and appears as a black and white 3D image.

Color Anaglyph -- The result is designed to be viewed using red/cyan glasses and appears as a color 3D image.

Left+Right -- The result is a side-by-side image consisting of the left image to the left of the right. This is the most common option for viewing with a prism or mirror viewer.

Right+Left -- The result is a side-by-side image consisting of the right image to the left of the left. This is the most common option for viewing with a prism or mirror viewer.

L/R -- The result is an over-under image consisting of the left image above the right. This option is required for certain types of mirror viewer.

R/L -- The result is an over-under image consisting of the right image above the left. This option is required for certain types of mirror viewer.

Left Only -- The result is the adjusted left image only. This option is useful when printing the images separately.

Right Only -- The result is the adjusted right image only. This option is useful when printing the images separately.

Image Spacing

This slider controls the amount of space between the two images -- it is not used for either of the anaglyph methods.

Background Color

This lets you set the color of the space between the two images -- it is not used for either of the anaglyph methods.

Tips

Stereo pairs of images are often created using a special stereo camera that takes two pictures simultaneously. For stationary subjects, however, you can get the same effect by taking two photographs with the same camera by offsetting the lens by approximately the distance between your eyes (roughly 2.5 inches or 60mm) or with two cameras mounted to a slide bar that holds them at a fixed distance from each other. This offset distance is called the baseline.

When photographing stereo pairs, the two exposures should be offset horizontally only. Assuming you can adjust the distance between the two cameras, the optimal baseline is roughly 1/30 of the distance to the near point of the scene. Values between 1/20 and 1/60 are also usable depending in the depth effect you want to produce. If the baseline is too long, you will have trouble merging the two images when viewing them. If it is too small, the depth effect is minimized.

You can extract the individual left and right black and white images from a black and white anaglyph with the Extract Channel transformation. To retrieve the left image, extract the red channel; for the right image, extract the blue or green channel.