Eye Wonder

We "see" the world through our eyes. We think and talk all about what we see, but have you ever thought about what you're NOT seeing? Our eyes, wonderful as they are, are very limited compared to some other creatures. This makes sense, as our eyes have evolved to suit our particular needs as a species. But, consider that:

- Humans see in only three colors. Some fish see five. (A very few human women are tetrachromats; they have four types of color receptors)

- Humans cannot see into the ultraviolet, like bees.

- Humans cannot see infrared, like pit vipers and some fish.

- Humans cannot easily detect the polarization of light, like ants and bees.

- Humans can see only in front of themselves. Many other animals have far greater fields of view; examples are sandpipers and dragonflies.

- Human vision is poor in the dark; the vision of owls is 50 to 100 times more sensitive in darkness. Some deep-sea shrimp can detect light hundreds of times fainter still.

- The range of distances on which one may focus is measured in diopters. A human's range is about fourteen diopters as children, dropping to about one diopter in old age. Some diving birds have a fifty-diopter range.

- The resolution of human vision is not as good as that of hawks. A hawk's vision is about 20/5; they can see an object from about four times the distance of a human with 20/20 vision.

- Humans have a blind spot caused by the wiring of their retinas; octopuses do not.

- The Four-eyed Fish (Anableps microlepis) has eyes divided in half horizontally, each eye with two separate optical systems for seeing in and out of the water simultaneously. Whirligig beetles (family Gyrinidae) also have divided compound eyes, so one pair of eyes sees underwater and a separate pair sees above.

- The vision of most humans is poor underwater. The penguin has a flat cornea, allowing it to see clearly underwater. Interestingly, the Moken (sea gypsies) from Southeast Asia have better underwater vision than other people.

- Humans close their eyes to blink, unlike some snakes.

- Chameleons and seahorses can move each eye independent of the other.

So, what would our lives be like if we had different eyes? Among many other things, think about the implications on our art. As an aspiring photographer, I can only grope at the implications for that field. Imagine being able to interpret a picture with 20 stops of dynamic range, or color from infrared up through ultra-violet, with polarization effects. I wonder what such a picture would "look" like to someone capable of interpreting it.

I'll never know, but I'll always wonder.