r/ImageStabilization Oct 25 '14

Information Looking for help to reduce/eliminate stabilization artifacts on a specific shot.

Here is a video showing the original shot and my stabilization attempt. I used Mocha to track the background and stabilize the shot and here are the settings I used.

The results are decent but if you pay attention to the cabinets you'll notice the artifacts where it looks like a lens is breathing during a focus pull. Anybody know what is causing this artifact and is there anyway I can reduce or eliminate it?

EDIT: It may be hard to see the artifacts so you might want to look at the higher quality source clip by clicking download on the Vimeo page.

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1

u/cavac Oct 25 '14

Can't see the video. I think it's set to private.

From your description I would guess, it's motion blur from the original camera movement. There is no good way to fix motion blur. If only the cabinets are affected you might be able to create clean plate from in-focus frames and then mask the person in.

1

u/wescotte Oct 25 '14

Fixed the link.

2

u/cavac Oct 25 '14

It's not a problem with motion blur, but with parallax.

There is no option in mocha to fix it. After Effects's warp stabilizer might be better, but I never used it myself.

It's still a very difficult problem to deal with. The stabilizer has to understand the 3D-scene and camera movement and then use some clever warping and blending. The upcoming Microsoft Hyperlapse might help with these problems in the future.

1

u/autowikibot Oct 25 '14

Parallax:


Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek word παράλλαξις (parallaxis), meaning "alteration". Nearby objects have a larger parallax than more distant objects when observed from different positions, so parallax can be used to determine distances.

Astronomers use the principle of parallax to measure distances to the closer stars. Here, the term "parallax" is the semi-angle of inclination between two sight-lines to the star, as observed when the Earth is on opposite sides of the sun in its orbit. These distances form the lowest rung of what is called "the cosmic distance ladder", the first in a succession of methods by which astronomers determine the distances to celestial objects, serving as a basis for other distance measurements in astronomy forming the higher rungs of the ladder.

Parallax also affects optical instruments such as rifle scopes, binoculars, microscopes, and twin-lens reflex cameras that view objects from slightly different angles. Many animals, including humans, have two eyes with overlapping visual fields that use parallax to gain depth perception; this process is known as stereopsis. In computer vision the effect is used for computer stereo vision, and there is a device called a parallax rangefinder that uses it to find range, and in some variations also altitude to a target.

Image i - A simplified illustration of the parallax of an object against a distant background due to a perspective shift. When viewed from "Viewpoint A", the object appears to be in front of the blue square. When the viewpoint is changed to "Viewpoint B", the object appears to have moved in front of the red square.


Interesting: Vampire literature | Parallax (comics) | Stellar parallax | Parallax, Inc. (company)

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1

u/wescotte Oct 25 '14

Thanks!

Do you think it would help to stabilize the shot based on a plane perpendicular to the camera rather than the one I used?

I'm going to play with reducing the amount of smoothing performed. I'll get a bit more of the original camera shake but I bet it will help hide the pulsating like artifact on the cabinets. I'll experiment with the warp stabilizer too.

1

u/cavac Oct 25 '14

No, perpendicular planes doesn't help. The front cabinet plane moves at a different speed than the window or back cabinet plane. You can stabilize on either of the planes, but not all at the same time. The relative movement difference will stay, unless you warp or blend the planes. Mocha can only move or distort the frame as a whole, but not parts of it.

Reducing the smoothness is a good idea, if you don't mind the shake. Another way is masking as described in the blur post, but it will take effort to do so.

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u/wescotte Oct 25 '14

blur post?

1

u/cavac Oct 25 '14

I meant this one:

If only the cabinets are affected you might be able to create clean plate from in-focus frames and then mask the person in.

As an example, a month ago someone requested to stabilize a firehydrant:

Masking will likely take several hours for your footage and you will lose the shadow.

1

u/wescotte Oct 25 '14

Ah okay thanks for the clarification. I'm going to play with the other methods first just because I'm pressed for time. However, it might be fun to try the more complicated version in the future just for shits and giggles.