Physiological vs. physical optics

In my last blog I talked about the resolution of the human eye.  That is all fine and dandy, but it is very important to remember that the eye does not function like a CCD or CMOS-based digital camera.  It does not snap pictures that it then stores intact in the brain.  The eye is part, an important extension, of the brain, and the brain is an image processing device that stores images in its own peculiar way, connects and combines them with other images, and connects them all with emotions.  When looking at a scene or photograph the eye doesn’t even stand still.  Rather it scans the scene picking out important recognition points.

Now I’m not an expert on this topic.  So I’m not going to dig myself in more deeply for risk of being inaccurate.  I just want to emphasize a few significant points.

  • First, when talking about the eye and brain, it’s important to recognize that you’re dealing with physiological and ultimately psychological optics, not just plain vanilla physical optics.  There’s even different set of units to describe physical and physiological optics.
  • Second, the brain connects an images and ultimately evokes emotion.  In a very real sense we feel an image.
  • Third, all of the aesthetic tricks of photography, the golden rule of thirds, the dynamicsm within an image, foreground/background flip, etc. are the result of what’s going on in the brain during image perception.

Of course, the eye, the brain, and all of the rules of physiological and psychological optics are ultimately determined by the physics and chemistry of the eye and brain.  But, and perhaps most importantly, without the brain and the way it processes there could be no photography, since it is the brain that accepts a flat image of a three dimensional world, even  images devoid of color, and enables it to evoke the same emotions as the original scene.*  It is the eye/brain that enables us to look at a photograph and say: “How beautiful!” – not just to say but to feel it.

*At the recommendation of a reader, I have been reading Timothy Egan’s biography of Edward Curtis, “Short Nights of the Shadow Catcher.  Egan records that in “December of 1904 Curtis rented out a large hall in Seattle and mesmerized the audience with hand-colored lantern slides and moving pictures of Indians of the Southwest.  The film prompted members of the audience to jump from their seats in fear.”



This entry was posted in Technical Aspects of Photography.