While there doesn’t seem to be a definite answer to this question, the number most often postulated is 576 megapixels. This is one of the more intelligent answers to the question: he’s writing from India, which explains dodgy spelling and grammar I suppose: It is wrong sense of calculation of human eye perception.
As you mentioned the human eye just sees the image. But the actual creation of image is done in by the nerves. (i.e.) In the neurons of the brain. So the picture what we see and the clarity is not a term. Which could be calculated in terms of pixels. As pixels are calculated in a mage created by a single entity or system.
But here it involves many parts of the body. In the creation of a human face the eyes, nose, mouth, checks, eyebrows, etc. They are stored in different parts of memory. So these parts are brought to a centralized place in the brains by the neurons. Then it is made as a picture and the person is interpreted as XYZ. All this takes place in few Nano second.
So pixel calculation is not done for the image created by the human brain. ya but many websites give theories and explaination, but if we find the correct meaning of the word pixel, and understand the neuron activity in brain, these websites expalination are all false.
Retina Of Human Eye
The average human retina has five million cone receptors on it. Since the cones are responsible for colour vision, you might suppose that this equates to a five megapixel equivilant for the human eye.
But there are also a hundred million rods that detect monochrome contrast, which plays an important role in the sharpness of the image you see. And even this 105MP is an underestimate because the eye is not a still camera.
You have two eyes (no kidding!) and they continually flick around to cover a much larger area than your field of view and the composite image is assembled in the brain – not unlike stitching together a panoramic photo. In good light, you can distinguish two fine lines if they are seperate by at least 0.6 arc-minutes (0.01.Degrees).
This gives an equivilant pixel size of 0.3 arc-minutes. If you take a conservative 120 degrees as your horizontal field of view and 60 degrees in the vertical plane, this translates to. 576 megapixels of available image data. Actually, 576 megapixels is for 120 degrees horizontally and 120 degrees vertically.
Curiously – as a counterpoint to this – most people cannot distinguish the difference in quality between a 300dpi and a 150dpi photo when printed at 6×4″, when viewed at normal viewing distances.
So: although the human eye and brain when combined can resolve massive amounts of data, for imaging purposes, 150dpi output is more than enough to provide adequate data for us to accept the result as photographic quality.
But don’t forget that women have more cones and men have more rods – I kid you not. Therefore the ladies see colors brighter than gents but can’t see as well when it gets dark.
Resolution Of The Human Eye
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 brains combine the signals to increase the resolution further. We also typically move our eyes around the 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. So the megapixel equivalent numbers below refer to the spatial detail in an image that would be required to show what the human eye could see when you view a scene.
Based on the above data for the resolution of the human eye, let’s try a “small” example first. 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 * 60 arc-minutes/degree * 1/0.3 * 90 * 60 * 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 * 120 * 60 * 60 / (0.3 * 0.3) = 576 megapixels.
The full angle of human vision would require even more megapixels. This kind of image detail requires A large format camera to record.