What is the Resolution of the Human Eye?

In a mathematically baffling, scientifically swerving 10-minute video, professional geek analysts Vsauce delve into comparing the universes of cinema and real-life to answer one seemingly simple question: What is the resolution of the human eye? Watch host Michael Stevens take a lengthy stab at it below:

First: What Is Resolution?

Stevens starts by defining megapixels as not equal to camera resolution. Though we often think of an image’s resolution as something like, for example, 1920×1080, resolution is actually determined by light, sensor size, what’s being encoded, and the subject’s proximity to the lens. Pixel density doesn’t even matter at a certain distance away.

So Stevens redefines the question as, “How many pixels would you need to fill your field of view to convince you you were looking at real life?”

Problems With the Question

There are a few problems with translating eyesight into technological terms:

1. Our eyesight includes–and automatically ignores–things like our noses or glasses, which are hard to replicate on-screen.
2. We all have a blind spot in each eye. (If you didn’t know this, close your right eye and move your thumb slowly from your central field of vision to the left–it will disappear, and it’s freaky.)
3. Our fovea: this refers to the central two degrees of our field of view, which are the only things in full focus at any given time.

Our eyes blur out noses and glasses, and focus on the middle of our field of vision.

That said, Roger M. Clark of Clark Vision did the math a few years ago and found that the answer, if you found a screen large enough to encompass your entire field of view, would have to be 576 megapixels dense.

But that number’s misleading, the author writes, because our eyes don’t function like cameras.

“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.” – Roger M. Clark

What that means is that the 576-megapixel screen assumes our eyes digest all visual information equally–which, when we consider that we only digest what’s in our fovea fully, we know just isn’t true. The image on the 576-megapixel screen would be too consistently detailed, when most of what we see is actually blurry.

What we see in our fovea sight range is actually more like seven megapixels.

Even when we can see a full field of vision, we’re only focusing on the center—including a blind spot, here marked by a black circle.

Outside that seven-megapixel fovea range, we’d only need one megapixel more to fool us. Which sounds like very little–until we remember that we simply don’t have the technology to accurately pull off a mechanism that would be able to fool our eyes like that, and the whole question is built on a silly and impossible premise.

Life is Not a Movie

Ultimately, Stevens concludes, the two are incomparable. In a touchingly philosophical finale, he pays homage to the distinction between real life and the world of film:

“Like a camera censor, we only have a finite and discrete number of cells in our retina. But the brain adjusts our initial sensations into a final perception that is a wishy-washy, top-down processed blob of experience. It’s not made of pixels and, furthermore, unlike a camera, it’s not saved in memory with veracity like a digital camera file….

“We play roles in the movie of life. But it’s a special kind of movie. Cinematic victories and struggles are often discrete, resolved, like pixels, with unbelievably perfect beginnings and endings. Whereas the real world is all about irresolution… Life doesn’t appear in any particular pixel resolution or narrative resolution. Things are continuous. The world was running before you came around, and it will continue running after you are gone.” – Michael Stevens