Hacker News
points by throwaway219450 3 days ago | 0 comments
There are odd visual illusions though, like humans perceive the Wagon-Wheel Effect even though there's no obvious reason it should happen. This is the effect where the speed of a rotating object varies depending on its sync with a discrete exposure period.

https://en.wikipedia.org/wiki/Wagon-wheel_effect

https://research.tue.nl/en/publications/subjective-strobosco...

[–] qqewqe123 3 days ago
You mention it yourself, these illusions only occur with "discrete exposure periods". This is moreso related to video recordings and less about how the eye sees actual physical objects. Such illusions do NOT occur with natural light.

Edit; to be clear there is a version of the wagon wheel effect under natural light, I'm just saying that the main one with discrete exposure periods does not occur irl

[–] throwaway219450 3 days ago
> You mention it yourself, these illusions only occur with "discrete exposure periods".

Have a look at https://www.pnas.org/doi/epdf/10.1073/pnas.93.8.3693; my point was that there is documented research that says even with continuous illumination and an (apparently) continuous camera (the brain), this happens:

> The illusion of wheels or other radial patterns rotating back- ward in continuous light, together with the perception of supernumerary spokes, suggests that the human visual system processes sequential episodes of information rather than a continuous temporal flow. In addition to accounting for this remarkable illusion, a strategy of vision that parses the world in this way can explain why movies are so realistic (simply because that is the way we normally see things) and how we detect motion (by comparing the position of the same objects in sequential episodes).

[–] 1718627440 3 days ago
What? Have you never looked at another car's wheel on the highway? Or is that something that only occurs to some people (doubt it).
[–] autoexec 3 days ago
Eye vibrations can cause the effect to be visible to the naked eye. If even humming can do it, the road vibrations might too.
[–] 1718627440 3 days ago
I'm confused. I thought seeing/measuring lower frequencies due to a low sampling frequency, where the lower perceived frequency is basically the modulus of the real frequency and the sampling rate, is a well-known phenomenon independent of the actual sensor implementation.
[–] autoexec 3 days ago
I guess it is, but it's unclear why it happens outside of recordings. https://www.livescience.com/32406-what-makes-wheels-appear-t...