Retinal images

Here's a nice way to get an idea just how much processing intervenes between retinal images and conscious perception. Unless you're reading this post through a screen reader or some other assistive technology, while you're reading the post, your eyes are moving in very fast saccades. So your retinal images are a mess. They are like a video produced by a camera that is waving around apparently randomly at high speed. But screen and the text on it looks to you as if it was basically still. You do not see the mess of retinal images with different orientations—they are all stitched together in complex post-processing into an image of something unmoving. Now, walk around while looking at some three solid and unmoving dimensional object in your environment. In addition to the shifts in retinal image produced by the eye motion, there are shifts due to head motion, due to the up-and-down rhythm of your walk, as well as the exposures of hidden surfaces. Yet the solid and unmoving object looks unmoving.

Of course, there are times when the post-processing fails—there are illusions of motion. For instance, because there is a background behind the laptop screen, and parallax ensures apparent relative movement of the laptop and the background, when I move my head, it does look like the laptop is moving relative to the background.

In any case, what we see does not look like what you get from a head mounted camera. And our retinal images are even jumpier than that, as the head mounted camera does not follow the eye-muscle saccades. We have some really quite amazing image stabilization.