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What can human eyes see?

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  • What can human eyes see?

    I wonder how large and in which form is the area that human eyesight can cover without rolling the eyeballs: the horizontal and vertical angles of eyesight. The angle from left to right and from up to down, and in which geometrical form? Do we see a round circle or an elippse or even a rectangular?

  • #2
    A single unencumbered human eye has a roughly circular field of view of ~150 degrees. A binocular pair registers the same 150 degrees vertically and ~180 degrees horizontally, so the total field is a slightly flattened circle.

    In reality the vertical fields are further limited by the cheek and upper orbital ridge (eyebrow).

    Of this only the central few degrees is detail vision (sharp) and corresponds to the fovea, the region in the retina with the highest populaion of photosensitive cells. The foveas very center, the "pit", has few color sensors with the others densely packed in a hexagonal pattern to increase sharpness.

    If you simulated this in a picture the sharp center would have muted colors and be surrounded by an increasingly blurry color rich zone to the periphery.

    Depending on the situation the contrast ratio can go as high as several million to 1. Average resolution: ~17,000 dpi.

    Dr. Mordrid
    Last edited by Dr Mordrid; 27 April 2006, 23:05.
    Dr. Mordrid
    ----------------------------
    An elephant is a mouse built to government specifications.

    I carry a gun because I can't throw a rock 1,250 fps

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    • #3
      Thanks a lot, Dr.! It was most helpful!
      I have two more questions:

      Could you please tell me a bit more about the angles of the central region (and with the limitations of cheek and eybrow)? I'm trying to compare human eyes with camera lenses and slide films in this issue. Is there any literature on this topic in the net you would recommand (only for layman)?

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      • #4
        wikipadia.org
        There's an Opera in my macbook.

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        • #5
          I visited it before I raised my question here. I didn't even find the information that Dr. gave me with the keyword "eye" in Wiki.

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          • #6
            you might want to check that site: http://neuro.med.harvard.edu/site/dh/b8.htm

            lots of informations there ...
            "Women don't want to hear a man's opinion, they just want to hear their opinion in a deeper voice."

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            • #7
              In traditional photography, a focal length of 50mm is considered to match the viewing angle and perspective of the human eye (not the extreme limits).

              Peripheral vision is one of the medical tests for a pilot.

              Jörg
              pixar
              Dream as if you'll live forever. Live as if you'll die tomorrow. (James Dean)

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              • #8
                Greetings from Boise!

                I'd like to throw a caveat into this thread...

                Tests of human visual acuity generally work around established ideals or norms, but the fact is that human visual acuity is wildly, wildly variable. Temporal problems such as being flashed by headlights at night or by the sun through trees can degrade sight substantially, and there have been actual cases (litigation) where the mitigation of visual acuity was determined to be a causative issue in accidents and such. In fact, I just did some work on such a case...

                Various pathologies also affect visual acuity...glaucoma, cataracts, macular degeneration and daibetes/hypertension are some of the better known. These are less temporal but no less variable in effect than, for example, watching television in a dark room for several hours, which fatigues your eyes.

                As if that's not enough, there's always age/presbyopia...

                So, I respectfully suggest that using a "standard" of eyesight, whether it be the ability to resolve detail, distinguish color, or establish a field of view for a static eye/s (monocular or binocular, in the absence of accomodation), can be very frustrating and is probably not to be trusted.

                Incidentally, a "model" human eye can provide reasonable scrutiny to about 26.5 degrees FOV...anything more inclusive generally requires accomodation. Calculating the total FOV for static, binocular vision is, or would be a nightmare dependent upon a ridiculous amount of factors ranging from the coordination of the eyes to the amount of ambient light, pathologies, and so on.

                Apologies for being wrapped around the axle...

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