The last post got a lot of responses (and we do love an adoring public), so now we'll share the secret to our stereoscopic animations.
Take this image from the fantastic Buffalo Olmsted Parks Postcards & Stereo Views collection:
In the Layers panel, you can adjust the opacity of one layer at a time. This is helpful for lining up the two halves of the stereoscopic image. Select a layer (it'll be blue in the panel when it's selected), and reduce the opacity to about 50%. Then you can move the layer around on top of the first layer to line up the outline. Don't line up the contents of the two halves, or you'll defeat the purpose of the stereoscope!
After adjusting the placement of your top (second) layer, return the opacity to 100%. In the main menu, under Window, click Animation. This will bring up a new tool panel called Animation. You can see the frames of an animation as you build it. You begin with one. Click the icon to create a new frame:
Now you have two frames in your animation panel. One shows the bottom layer and one shows the top layer. By default, the frames are set at 0 seconds each. Click on the frame in the animation panel and select 0.1 sec or 0.2 sec. Do this for both frames:
In the animation panel, you can press the play button for a preview of your GIF!