Wednesday, March 28, 2007

Human Eye Tech Specs reports: [edited]

How many megapixels does the human eye possess?
The eye is not a single frame snapshot camera. It is more like a video stream. The eye moves rapidly in small angular amounts and continually updates the image in one's brain to "paint" the detail. We also have two eyes, and our brain combines the signals to increase the resolution further.

We also scan a scene to gather more information. Because of these factors, the eye plus brain assembles a higher resolution image than possible with the number of photoreceptors in the retina.

Consider a view in front of you that is 90 degrees by 90 degrees, like looking through an open window at a scene. The number of pixels would be 90 degrees x 60 arc-minutes/degree x 1/0.3 x 90 x 60 x 1/0.3 = 324,000,000 pixels (324 megapixels).

At any one moment, you actually do not perceive that many pixels, but your eye moves around the scene to see all the detail you want. But the human eye really sees a larger field of view, close to 180 degrees. Let's be conservative and use 120 degrees for the field of view. Then we would see 120 x 120 x 60 x 60 ÷ (0.3 x 0.3) = 576 megapixels.

ISO Sensitivity of the Human Eye
After 30 minutes darkness: ISO 800. In bright sunlight, over 600 times less, which would put the ISO equivalent at around 1.

The Dynamic Range of the Eye
The eye is able to function in bright sunlight and view faint starlight, a range of more than 10 million to one. The eye is a contrast detector, not an absolute detector like the sensor in a digital camera. The range of the human eye is greater than any film or consumer digital camera.

The Focal Length of the Eye
Object focal length of the eye = 16.7 mm
Image focal length of the eye = 22.3 mm

Thanks to Sora for the loan of her (very beautiful) left eye.

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