Eye Versus Camera

Metaphors are essential to writing about science. Even scientists themselves use metaphors all the time, drawing from their familiar experiences to describe the unfamiliar. Building proteins is known as translation, for example, because the sequences of DNA and proteins are akin to words written in different languages. The cell has to translate one language into another using–another metaphor–the genetic code.

Metaphors can be powerful, but they can also trip us up if we mistake them for an equivalence. DNA isn’t really a human language, for example. In my latest column for Discover, I take a look at another tricky metaphor: the eye as camera. Some scientists are actually making that metaphor real, by building video cameras that can let blind people see. As I point out, however, eyes are not cameras, and the differences are fascinating. They’re also crucial to the future success in treating blindness with technology. Check it out. 

6 thoughts on “Eye Versus Camera

  1. All analogies eventually break down. If one doesn’t, it’s not an analogy – it’s the thing you’re talking about.

    If one looks at a solar eclipse (the Moon is in front of the Sun), one sees solar flares and the much dimmer corona. To get that in a photo, one must take two pictures with different exposure times and combine them in post processing. That’s because the eye has much better dynamic range – faint and bright – than modern cameras.

  2. Quite. But sometimes, as in the example of the genetic code, the abstract exists too. I.e. it is in fact (also) a code as information theory sees it.

    @ Stephen:

    I know what you mean I think, but you broke “identity” in your analogy. If it isn’t an analogy, it is an equivalence. But over groups.

    I.e. a dog is a wolf analogue, and in as much as they derive from the same ancestor they are canines. But one dog is only equivalent to another dog, they are not the same individual.

    I guess I’m saying that “thing” can refer to different things!? Language is amazing!

  3. It is not with only dynamic range that the eye is better than a camera, but “white balance” as well. Few people realize just how much the eye/brain correct for “off” colors until they take a photo indoors under existing light without a flash. The resulting image is what the eye actually “sees,” but the brain does a wonderful job of “correcting” the colors to make white look, uh, white.

    New technologies like high dynamic range post-processing are making progress in that area to allow more detail in areas previously difficult to capture. White balance remains an issue, especially in photos made with mixed lighting, such as someone indoors near a window. Your brain fixes this image easily, while photographic methods still struggle with this type of scene.

    The future of “bionic eyes” will be interesting to say the least. With the eyes being only half of the system, the existing brain/processor will likely surprise us with how much it can do with even the most basic of sensors.

  4. very nice summary. Vision is very complicated. One area you mention briefly is that in the prostheses the scientists are stimulating the output cells of the retina (the ganglion cells) as if they directly receive the photo array. As you point out, there is, in fact, a great deal of processing in the retina between the photo-receptors and the ganglion cells, and the transform is not well understood. Many problems, but very exciting work.

    But there is one fundamental way that the eye is like a camera. In each light travels in straight lines from objects through an small hole (aperture/pupil) to a planar receptor surface. This permits the inference of the shape, size, distance and location of objects relative to the viewer. The eye is one of the great achievements in evolution. And the camera does a good job in copying the basic design.

  5. “The eye is one of the great achievements in evolution.”

    This is one of those ultimate metaphors; evolution doing something.

    But alas, even skeptics need a god.

    [CZ: As long as the metaphor’s clear, I don’t see a problem.]

  6. I find many of the designs in nature remarkable and, if done by a thinking being, extremely clever. To admire the design, and to consider it an achievement, is not to say that the process is supernatural or involves a conscious inventor.

    In a similar fashion, I find the Grand Canyon awesome and beautiful. But I can have this feeling without the notion that it was designed by an artist.

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