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A normal camera can capture a rectangular image. If human eyes watch an area, what's the shape of the captured region? Rectangular? Half-spherical?

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    $\begingroup$ The info posted about retinal response shape area is quite useful, but when you ask about the shape of the image you perceive, you are diving head-first into the neurological field of optical sensing. What little I know is that what we "think" we see is largely made up out of history and good guessing by our optical processing center in the brain. Our apparent perceived region is somewhat less than a hemisphere IIRC. $\endgroup$ – Carl Witthoft Nov 15 '14 at 21:53
  • $\begingroup$ Mapping the output of a camera's photon sensors as a rectangular grid of pixels is an explicit and arbitrary decision made by the designer of the camera (and driver/firmware architects). Because the output of a human eye is not visualized on a monitor, and consciousness itself is a very controversial phenomenon, I think this question is ill-posed. A better question would be, "how does human visual acuity change over the FOV?". $\endgroup$ – Superbest Nov 16 '14 at 0:07
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    $\begingroup$ @Superbest On the other hand, regardless of how the sensory input is used, the eye still, physically, has a definite viewing volume (i.e. a definite range of angles such that photons passing through the lens at those angles interact with the retina). E.g. no matter how you feel about consciousness, a ray of light arriving at the back of your head will not strike your retina. $\endgroup$ – Jason C Nov 16 '14 at 7:01
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The capture area of the eye is a bit fuzzier and harder to define than that of a camera.

A camera captures consistent, fully detailed data right up to the edge of its sensor, and no data at all beyond it. Captured data is clipped by an ideally uniform sensor, augmented a bit by the lens, and is well-defined during design and manufacturing.

The eye can capture higher "resolution" near the center of its capture area and also has very little information about color near the edges (see also Peripheral Vision); so it's not quite as clean cut depending on your goal of "capture area". The eye also has a bit of a "blind spot" near the middle, which our brains basically Photoshop out. Additionally, it varies from person to person.

The effective capture area would really depend on your application (e.g. the "capture area" for, say, reading text, would be narrower than the area for, say, detecting motion).

Here is a typical diagram for a single eye, showing just the ability to see something in that area (does not show details related to peripheral vision quality):

enter image description here

Here is a typical diagram for both eyes combined, the solid white area is the overlap:

enter image description here

Both of those images are from a 1964 NASA report detailing aspects of the human visual field. If you want the detailed answer to your question and more, you probably want to take a look at that.

Note that our field of vision is very wide, those diagrams may not do it justice. As an experiment, close one eye, stare straight ahead and hold your arms straight out to the sides. Wiggle your fingers and slowly bring your arms forward until you can just see your wiggling fingers in your peripheral vision, and you will get an idea. As an added experiment, hold a piece of paper with text on it, and repeat the same experiment until you can read the text - this region will be extremely narrow and will give you an idea of how the quality of vision changes across the field. Also try with a colored object and bring it in until you can clearly identify the color.

There are also some simplified mentions of it in wikipedia:

A good set of search keywords is "human field of vision". There is also a nice related article entitled The Camera Versus the Human Eye.

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    $\begingroup$ Great answer, but the illustrations hide (as you say in the text) the order of magnitude difference in resolution between the middle of the field and the sides. For a camera, all of the pixels are almost equal, for an eye they are not. $\endgroup$ – Peteris Nov 15 '14 at 21:21
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    $\begingroup$ Perhaps add a reference to how the brain makes you feel you have a more cinematic and even visual field (more Photoshopping) e.g. en.wikipedia.org/wiki/Saccade - this depends a little on what the OP means by "watch an area". Unless effort is made to keep eyes still, watching is naturally and unconsciously an active scanning process. Edit: Scratch that, that is very nicely covered in your last link (The Camera Versus the Human Eye). $\endgroup$ – Neil Slater Nov 15 '14 at 23:11
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    $\begingroup$ +1 for making me roll my eyes around until I realized I can't see my cheek, but I can see my mustache. $\endgroup$ – rob Nov 16 '14 at 0:46
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    $\begingroup$ The link to the 1964 NASA report is now broken; if someone can find a better link (or a real citation) that would be a nice update. I tried but failed. $\endgroup$ – eclarkso Nov 8 '18 at 14:52
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    $\begingroup$ @eclarkso Thanks. I've replace it with an archive.org link. $\endgroup$ – Jason C Nov 16 '18 at 23:33
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One eye captures a roughly circular area. Because we have two overlapping fields of vision for depth perception, between our two eyes we capture a roughly elliptical shape.

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    $\begingroup$ To add to this - Cameras capture in rectangular shapes because that is the shape of their CCD sensor, so I imagine that the shape of an image received by an eye will correspond to our "sensor" i.e., our optical nerve. $\endgroup$ – Kitchi Nov 15 '14 at 17:59
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    $\begingroup$ @Kitchi Picking anatomical nits: Our "sensor" is called the retina. The optic nerve itself cannot sense light. $\endgroup$ – Jason C Nov 15 '14 at 19:14
  • $\begingroup$ @JasonC - Ah, right. Thanks! I thought the retina was part of the "optics", i.e., the focusing and lenses etc. $\endgroup$ – Kitchi Nov 15 '14 at 19:22
  • $\begingroup$ @Kitchi Indeed, the spot where the optical nerve is attached to the retina is called the blind spot, as mentioned in Jason's answer. (The demonstration on that page is pretty cool by the way – try it out.) $\endgroup$ – ntoskrnl Nov 15 '14 at 21:11

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