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