Eye / Brain

I hope this never happens to you. Still, it's instructive.
The eye is only half of the apparatus we have for apprehending the universe. How do we make sense of what we see? It's not only a series of shaky blurs and swathes of color, but an actual space we can understand and move in, and react to. Credit for this goes to the brain, which synthesizes a 3D map of what we see and it is this map - not the glimpses and fragments we actually see at any given instant - which creates our act of seeing.
Whew... that's pretty heady. Specifically, we all know the adage that the 24 frames per second of film, or the 24 drawings of an animation 'blur' into motion when we watch - therefore we can experience the 'magic' of cinema motion from a series of stills due to the short time lag that the retina (see above) emits a signal after light hits a cell. This afterglow is easily noticeable if you hold your hand up by a lamp (at night) then turn off the lamp. You will see the outline of your fingers for a surprisingly long while...
But as you might guess from the above paragraphs, it's a wee bit more complex.
Even from still images, we build up a mental map and use this to synthesize the cinematic space. We assimilate this to 'natural motion' and smooth out the judders.
In cinema (not in video, though) there's also the question of flicker: though there are indeed 24 frames per second, these images are separated by shorter sections of black (due to the shutter closing and blocking out the light while the next image is lined up), so in an actual movie theater, we are watching an alternating flickering of image and darkness.
I find this quite romantic..
Tomorrow, we will look at the various factors we use, looking out of just ONE EYE - to gauge distance, hence depth. See how many you can think of.
Clue: remember Father Ted and the sheep...