Here's the two frames we're starting with. You'll remember them from the last series of steps.

Left Right

This is the most critical part of the process, since the 3D illusion depends on precise alignment between the two images.

  1. Make either of the images the foreground window. From the Edit menu, choose Select All (or you can use a keyboard shortcut: Command-A on a Macintosh, Control-A in Windows) to copy the entire image into the clipboard. We tend to perform this first step on the cyan image, so that the red image will be the background layer.
  2. Select Copy from the Edit menu (or Command/Control-C).
  3. Select the other image window (for us, this is the red image.)
  4. Choose Paste from the Edit menu (or Command/Control-V). The image will be pasted into a new layer, centered in the existing window and placed above the layer that was selected, usually the Background layer.
  5. Repeat the same copy/paste procedure (and layer rename) with the other image. Then double-click on the Background layer, click OK on the resulting dialog box, then drag the layer into the trash. (This removes the "specialness" from the layer so that it can be deleted.)
  6. When you are finished, your Layers palette should look something like the image on the right:

  7. The Layers palette context menu. The Layers palette.

  8. For the moment, your image just looks like the red image (if you've set the red layer on top, as in this example.) We'll change that now, using Photoshop's ability to change the way layers are blended.
  9. Using the Layer Options menu shown above, select the top layer and change its blending mode to Screen. (The Photoshop Help guide explains that Screen mode "looks at each channel's color information and multiplies the inverse of the blend and base colors. The result color is always a lighter color. Screening with black leaves the color unchanged. Screening with white produces white. The effect is similar to projecting multiple photographic slides on top of each other.")

  10. Change Layer mode to Screen...

  11. Amazing difference, isn't it? Note that, as promised, the color effect has returned, with some edge effects that come from the 3D process. This is because the final image once again has all three color channels present.
  12. Look through a pair of 3-D glasses and manually tweak the location of one of the images (use the arrow keys while the Move tool is selected) until the 3D effect is optimized.
  13. Crop all white space around the edges of the two images (draw a box around the two images, excluding whitespace, then choose Crop from the image menu.)

And now we'll have our completed image, which can be viewed in both red/green and red/blue glasses (red lens on the left). Do you see any depth in this picture? (Note that objects which are pure grey due to lack of offset from image to image - in this case, the arm and the object being held - appear to be exactly in the plane of the viewing screen.)

All done! (see also the full-size image - 100K JPEG)

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