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The [stroboscopic effect][1] is often explained as one of the problems of sampling. If sample rate is too low, you might have the impression of the signal frequency being low or even reverse. There are many animations on the internet describing the process but I find static sinus function graph more comprehensible:

stroboscopic effect sinus wave

You definitely know this effect from car wheels or plane propeller in movies. That's because the movie captures certain amount of frames. If the event is significantly shorter than capture rate, the output doesn't make any sense anymore.

My question is, how can I observe the stroboscopic effect in full light with my very own eyes? I thought there's no fixed frame-rate for human vision. I thought it's an analogous process (continuous stream), rather than digital (timed sampling).

  • Q: How can be human vision in non-flashing (such as sun) light be subject to stroboscopic effect? Where does the damage happen?
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  • $\begingroup$ @Krysta your edits suggest I assume there is a sampling. I do not assume anything. $\endgroup$ – Tomáš Zato - Reinstate Monica Dec 3 '14 at 15:00
  • $\begingroup$ That is why I said "effective" sampling rate--it doesn't mean there IS one, it just means that somehow it ends up looking like there is one. $\endgroup$ – Krysta Dec 3 '14 at 15:00
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Yes, you can experience the stroboscopic effect under continuous illumination. This wikipedia article does a nice job of summarizing relevant findings.

As mentioned in the article, there are two competing theories for how the stroboscopic effect happens under continuous illumination in the human visual system. The first theory is that human visual processing is like a movie camera and it operates on roughly discrete frames. The second theory is that neural adaptation is responsible: the brain adapts to the very regular patterns of motion, which can cause visual after-effects where the opposite pattern is perceived. Overlaying the actual motion with the visual after-effect will 'cancel out' the perceived motion.

Kline and Eaglemen (2008) present evidence against the discrete sampling hypothesis and supporting the adaptation hypothesis. Macdonald et al. (2014) present evidence for the discrete sampling account.

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  • $\begingroup$ So there are only theories without any evidence? $\endgroup$ – Tomáš Zato - Reinstate Monica Dec 4 '14 at 10:03
  • $\begingroup$ No, there is evidence for both theories. There's just no conclusive demonstration that either theory is wrong. $\endgroup$ – Josh de Leeuw Dec 4 '14 at 12:46

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