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If it could be possible to build a camera inside a human brain that takes photos of what we see. What would be the resolution of those images in terms of pixel count?

This question is not about numbers but rather showing a physical way to obtain an answer. If we pick a person, how can we find that particular person's vision resolution? Would it always be the same? Or is it depend on the distance to the item this person is focusing on?

Assume the person is closing one of his eyes, and he does not need glasses.

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The upper limit on angular resolution for the human eye is about 0.008 degrees, based on the Rayleigh diffraction limit for light entering the pupil. The binocular, central field of view is about $60^\circ$ vertically and $120^\circ$ laterally, so if you divided that up into the smallest cells it would be possible to resolve with human-sized pupils, you'd get about 112 million "pixels."

Of course, human eyes don't work nearly that well, so this is just an upper limit. Most humans have a visual acuity which allows them to distinguish objects separated by about 1 arc minute, or about $0.016^\circ$ - twice the diffraction limit, which would mean only about 28 million "pixels."

I'm not really sure what you mean about finding a physical way to obtain an answer. If you mean you want to measure somebody's visual acuity - that is, the smallest angular separation they can resolve - then optometrists do that every day. It's also worth noting that eyes don't have pixels, and that angular resolution depends on where in the visual field the objects are located, lighting conditions, etc.

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  • $\begingroup$ Can you please tell me more about how the optometrist finds the smallest angular separation a person can resolve and how "the angular resolution depends on where in the visual field the objects are located"? This is what I meant by "a physical way". Your analogy to optometrists sounds way better. $\endgroup$
    – Ilya Gazman
    Commented Jan 8, 2021 at 13:14
  • $\begingroup$ @IlyaGazman Have you ever had your vision tested? The result usually aren't phrased in terms of angular resolution, but that's what is ultimately being measured in those tests. Also, I mean that what details can be resolved depends on whether you're looking straight at something or if you are looking off to the side. Talking about human visual resolution in terms of pixels ultimately doesn't make a lot of sense, because vision and our processing of images is much more complex than a display screen or digital camera. $\endgroup$
    – J. Murray
    Commented Jan 8, 2021 at 13:19
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What is the pixel resolution of a human eye?

The human eye does not have pixels; the way it handles colours is very different to a digital camera; the way it adapts itself to low light levels is also very different; and what we perceive when we "see" something depends as much (possibly more) on complex processing within the brain as on the image on the retina.

So your question is more or less impossible to answer because the human eye and the human vision system has little or no resemblance to a digital camera. It is like asking "if we could taste numbers, how many numbers could we taste ?".

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The current technology does not accomplish what you have asked for but rather the opposite of it i.e. prosphene. We can convert images to electrical signals to enable visual prosthesis, this means is that conversion of electrical signals into neural spikes is possible and if you have heard of neuralink this what they are precisely doing.

So we can convert images to neural spikes by electrodes and vice versa. But how exactly neural spikes will translate to resolution or pixels is not something which have been predicted as far as I know. The thing is human eye does not have "pixels" so its not something we can predict without significant developmet in the biotech. What we know present is sort of an approximate, we can't really prosphene an image accurately so reversing the process is likewise an unknown territory.

PS: I don't have a solid background in biotech and my answer is based on my knowledge on visual prosthesis. I would suggest you to ask this question on Biology stackexchange as there you might get a better answer from someone working in that specific field.

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  • $\begingroup$ I am not looking for the biological side of this but rather the physical. Replace the human with an alien robot that speaks English. What experiments can you run on it to find it's visual pixel resolution. $\endgroup$
    – Ilya Gazman
    Commented Jan 8, 2021 at 3:03
  • $\begingroup$ @IlyaGazman And what would that tell you about the subject of your question - human vision? $\endgroup$
    – simon at rcl
    Commented Jan 8, 2021 at 10:10

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