How NOT to Stabilize

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‌How NOT to Stabilize

Though it is relatively easy to rig up a node-based compositor to shift footage back and forth to cancel out a tracked motion, this creates a fundamental problem:

Most imaging software, including you, expects the optic center of an image to fall at the center of that image. Otherwise, it looks weird—the fundamental camera geometry is broken. The optic center might also be called the vanishing point, center of perspective, back focal point, center of lens distortion.

For example, think of shooting some footage out of the front of your car as you drive down a highway. Now cut off the right quarter of all the images and look at the sequence. It will be 4:3 footage, but it’s going to look strange—the optic center is going to be off to the side.

If you combine off-center footage with additional rendered elements, they will have the optic axis at their center, and combined with the different center of the original footage, they will look even worse.

So when you stabilize by translating an image in 2-D (and usually zooming a little), you’ve now got an optic center moving all over the place. Right at the point you’ve stabilized, the image looks fine, but the corners will be flying all over the place. It’s a very strange effect, it looks funny, and you can’t track it right. If you don’t know what it is, you’ll look at it, and think it looks funny but not know what has hit you.

Recommendation: if you are going to be adding effects to a shot, you should ask to be the one to stabilize or pan/scan it also. We’ve given you the tool to do it well, and avoid mishap. That’s always better than having someone else mangle it, and having to explain later why the shot has problems, or why you really need the original un-stabilized source by yesterday.

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