People who live in glass houses…

But this isn’t about stones! It’s about image data getting cut off by the side edges of an image pair. Imagine looking out your window. It is natural that the window prevents you from seeing objects outside the window that are larger than what you can see through the window. Tree branches for example disappear at the window’s edge. One eye sees more of it than the other so you interpret the information as – the branch doesn’t end, it’s just out of view.

Now if that branch poked through the window into your room it might be impressive, but if it also disappeared right at the visible edge of the window that would seem strange. In physical reality that wouldn’t happen. If the branch intruded into the room, it would exist in front of the window edge and you could see that.

In a stereo image pair, the image information ends at the picture’s edge. You break the window when it seems the edge data shows something in front of the window, but which disappears magically at those side edges. It is illogical to the mind and becomes a distraction during stereo viewing.

A well composed and framed stereo image will attempt to insure that this doesn’t happen.

Below is an image that is well composed, but it has one little detail that does break the window. It can easily be ignored because it is not large nor is it part of the main subject matter. This makes it a good example to illustrate the point.

Garden Through the Window

This image pair is a Screen capture from the main panel preview window. The images were cropped leaving two pixels all around each image so you can see how to test for this window property as you edit your images. If you fail to include the side edges of the preview, you will have no idea whether the parameters correctly provide a stereo window for your image pair.

In this case, the windowing is correct and the parameters for both sides are correct and ready for a full resolution render.