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I just learned that in video cameras, every frame of the video has its own shutter speed.

shutter speed vs framerate

And I know how frame-rate in human eye works out, well, not completely, hence the question.

http://en.wikipedia.org/wiki/Frame_rate

The human eye and its brain interface, the human visual system, can process 10 to 12 separate images per second, perceiving them individually.

How much (or what is the equivalent of) shutter-speed in those individual images?

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The light receptor of the eye is a protein called Rhodopsin. To me the equivalent of shutter speed for the eye is the (de)sensitization of rhodopsin by phosphorylation. The brighter the light, the more sites on rhodopsin are phosphorylated, diminishing the intensity of the signal coming from the photo receptor via the transducin G protein that conveys the visual signal onward.

This process takes a few seconds, but then it's possible to see when stepping into sunlight or in a darkened room.

This is more like a volume knob than a shutter speed since the same signal comes out at the same rate of each light sensor, but it has a similar effect — it modulates the intensity of the image.

Actually I feel dumb but there is a simple answer to this question. You can get lost in the above physiology. The simpler answer is about 20 fps. Whenever strobing stops and persistence of vision takes over to create a continuous image is an interesting way to answer this question. That's how television and movies (and videos) work. 30 fps looks pretty smooth. It's not a perfect answer because 60 or 100 fps are functionally useful for situations like video games where fast reaction time is important.

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    $\begingroup$ If we are comparing with a camera, I would say this is more like the ISO rather than the shutter speed. $\endgroup$ Commented Nov 28, 2022 at 2:43
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    $\begingroup$ good point. the right answer might be the speed with which the optical nerve assembles the information from the eye. that is harder to explain or define though. nerves each act independently and do not synchronize the way a machine does. $\endgroup$
    – shigeta
    Commented Dec 17, 2022 at 7:39
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There is nothing comparable to a shutter of the camera in the eye. The eyelid is like a lens hood. When the eyelid is open the image is continuously projected on to the retina unlike in a movie camera. However if the question is on frames per second (number of static images) required to produce a sense of seamless motion this article might be of some help. In video camera instead of a shutter speed it is the number of times the image on the sensor is sampled(recorded) per second electronically. The eye is more similar to a video camera. The retina has rods and cones which has variable 'refresher' rates which makes it more complicated to calculate exact figures.

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Not all of your rods/cones fire at any given moment. Exception is when a bright flash of light is viewed. Recovery time from the resulting flash blindness is pretty slow -- seconds. But there's some photobleaching there, so maybe that's not fair.

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