Sunday, August 11, 2013

All Is Not As It Seems

The tag-line/motto that I use conspicuously here on this blog claims that the core reality of photography lies at the interaction of light and matter, the intersection of energy and mass. I have been thinking about this recently in relation to how physical and biological systems detect light. 

I mentioned previously here that I had been reading about the Stiles-Crawford effect and in doing so came across detailed descriptions of the infinitesimal workings of the light-sensitive cells– the cones and rods– of the human eye. Within these cells are contained micro-miniature energy conversion plants, material manufacturing facilities, and supply transportation pipelines. And below it all is an incredibly intelligent organization scheme, or command structure, which keeps it all running smoothly and efficiently. 

The functional regime which I casually referred to as an "energy conversion plant" is what is directly responsible for the all-important light sensitive aspects of the eye. As photons from the external world flood into the eye they are organized and redirected into the formation of a replica image on the retinal surface at the back of the eye. This retina, which some liken to the film in an old-school camera, is the organ of the eye which is responsible for taking these tiny packets of light energy and transforming them in a near-miraculous manner into electro-chemical energy signals that are sent to the brain for further transformation and analysis. 

Embedded in the retinal tissue are the light sensitive organelles themselves: the rod and cone cells. Within these tiny electro-optical instruments are organic dye materials, the molecules of which are stacked disk-like in the rod cells as if they were columns of Necco wafers and in the cone cells like leaves that are being dried as they lie interleaved in the pages of a thick book. The electro-chemical bonds of these stacks of dye molecules become excited as they absorb the incoming photons and their energy. The photons themselves die and are no more, while the dye molecules'  new-found energy is passed along the length of the cell, becoming the electronic signal that can be passed to outside systems. The signal continues along the electro-chemical pathway that comprises the whole of the optic nerve and into the brain itself.

NECCO Wafers, © New England Confectionery Company (NECCO)
What provoked my thoughts in all this is the commonly heard analogy of eye and camera. How often it is said that "the eye is like a camera, with its lens, iris, dark chamber (camera obscura), and light sensitive film at the back"– as if the camera were the foundational and superior system. We reason that a modern camera, with all of its incredible complexity, inter-working systems and subtle design, must be the pinnacle of imaging systems and data management, and think the eye to be a mere semblance of such obvious engineering excellence. 

But as it turns out so often, not much is like it seems. My years of working around and with vision scientists, and seeing some of the results of their experiments, have taught me that the human visual system ("system," because it entails so much more than simply the eye) is an incomprehensibly complex and subtle creation. The interplay of multitudinous features and schemes leaves one breathless when trying to understand how they all relate. And the engineering and design philosophies (if one can use those terms) underlying the whole system should make any self-respecting engineer (whether optical, mechanical, or electrical) blush with embarrassment at her own feeble attempts. 

My point here is not to disparage the engineer (I am one!) but to point out the simple fact that when it comes to imaging and optical information systems, the human eye and its larger visual system is without peer in this wide world, and perhaps, in this wide universe. At least we've not yet seen anything which beats it.  Some cameras, or even other biological visual systems, may exceed human vision in a particular narrow technical aspect, but nothing exceeds its overall performance, utility, and flexibility. 

So, enjoy your modern (or old-school) camera for what is, but never lose sight of the matchless design and astounding craftsmanship of the visual system that opens its two "shutters" for you each morning. 

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