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I always wonder, looking at certain movies (but especially TV commercials), why oversampling is not reduced someway. I think that you can recall any scene, both in movies or in TV commercials, in which there was a vehicle that proceeds afterwards, but its tyres seem to move backwards.

An example could be found in this video (even if it's nor a movie and a commercial):

Now, I understand that in movies this can be difficult to adjust: if it is an action scene, and the vehicle must be driven in a chase, or a context with explosion effects, it's almost impossible to synchronize car's speed and camera sampling. But in many TV commercials, with a scenery that is somewhat static, many times cars look to be proceeding backwards. Wouldn't it be sufficient to regulate the car's speed in respect to camera's sampling? Or maybe filming the car at different, progressive speeds and then cutting out the parts for which the speed is outside the range for which direction appears to be the right one?

More generally, do techniques exist in order to eliminate this phenomenon? And, if yes, why are they not always used?

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  • This is off-topic for this exchange. This should be migrated to Physics.
    – Jason P Sallinger
    Jan 28, 2020 at 15:22
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    @JasonPSallinger This seems to be very much a question about producing and altering films. Can you be a bit more specific in which way this would be off-topic?
    – Napoleon Wilson ♦
    Jan 28, 2020 at 15:40
  • This has little to nothing to do with any production of TV or movies and everything to do with the optics of a camera.
    – Jason P Sallinger
    Jan 28, 2020 at 16:33
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    @JasonPSallinger Movies are often produced with the aid of a camera.
    – Acccumulation
    Jan 29, 2020 at 0:01
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    @JasonPSallinger A question doesn't have to be about a particular movie of program to be on topic. Nor does it involving matters on-topic for another SE mean it isn't on-topic here. Moreover, it involves more than physics; it involves practical matters involved in making movies.
    – Acccumulation
    Jan 30, 2020 at 5:24

1 Answer 1

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This is a question of Frame Rate vs Speed. You can't just adjust frame rate to match speed, it's either 24FPS, 29.97FPS or 60FPS. You can't adjust that, unless you film in super slo-mo and adjust it later. But really, why go through that trouble when it doesn't hurt or hinder the shot? It'd been used in helicopter scenes since forever, and no one ever had an issue with it.

You'll notice the effect is eliminated once a car slows down. if you wanted to eliminate it, you could theoretically have the chase at 30MPH and speed up the film, but the resulting effect would be more undesirable than the current effect.

This used to happen with video of computer monitors or TVs, until refresh rates changed frequency.

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  • it's not QUITE the same as the rolling shutter phenomenon, but it's close: youtube.com/watch?v=dNVtMmLlnoE
    – DForck42
    Jan 28, 2020 at 15:40
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    I'm curious why no one in this thread has used the correct term for the phenomena: Stroboscopic effect. For me at least, the term explains the effect
    – user18935
    Jan 28, 2020 at 18:15
  • Thank you. I have no knowledge in cameras, and I did not considered the limitation in frame rate, that is bounded to fixed values.
    – Andrea
    Jan 29, 2020 at 11:03

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