Seeing Spots Even When Eyes Are Closed

What Is The Resolution Of The Eye

Hey, Vsauce. Michael here. I am at the White House, in America's capital, Washington, D.C. America makes a lot offeature films every year Hollywood. But they don't make the mostfeature films every year. Nigeria makes more. But the country that makes the mostfilms every single year is India. Every two years, the country of India fills up enough film with uniquefeature films that stretch all the way from this city,Mumbai, to where I live,

in London. That's double what Hollywoodproduces in two years. That is a lot of movies, but is reallife a movieé I've discussed the framerate of the human eye before but how does the resolution of the human eye compare to a camera or screené VHS, LaserDisc, DVD, Bluray, IMAX. Numbers like these arepixel dimensions. When multiplied they tell us the total number of pictureelements an image is made up of.

A figure often used to describe digitalcameras. It might sound like more is better, but to be sure numberslike 1920 by 1080 are not resolutions per se.More pixels is only part of the equation. Resolution is about distinguishing fine details and that depends on a lot of other factors. For instance, the amount of light, thesize of the sensors, what the millions of pixels are actuallyencoding and how close the subject is. I mean, up close

Salvador Dali's painting of his wifelooking at the Mediterranean can be resolved into boxes. But from a far, well, it's Abraham Lincoln. For crying outloud, on a small enough screen from far enough away, low and high,socalled resolutions on screens, aren't even resolved differently from one another by your eye. How different nearby pixels are from oneanother also matters. This is called spatial resolution.

For instance, if I go outoffocus the number of pixels in the tutorial framestays the same but you can't resolve as much detail. Now, with all this in mind we can still compare human vision to a digital image,by asking a better question. Assuming everything else is optimal, howmany pixels would you need to make an image on a screen large enough to fillyour entire field of view look like real life, without anydetectable pixelationé Now we are getting somewhere.

Kind of. The analogy is still crudy because a camera snaps an entire frameat once, whereas our eyes move around. The brain amalgamates their constant stream of informationinto what we call vision sight. In fact, the image created by theeyeball alone during a single glance would hardly even be acceptable on abroken TV screen. We think our eyes create images like this pictureGuy took of me with a camera. But for one thing, unlike a camera,you've got some stuff

Can You Trust Your Eyes

Our perception of the world around us isstrongly linked to our vision. But how do you know what you're seeingis realé Can you really trust your eyesé Take for example these two greyrectangular columns, both of which are different shades ofgrey. Or are theyé It turns out that they're the exact same. And yet, even after knowing the illusion is there your eyes refused to see them as thesame. Introducing colors produces the same result.

I promise no trick photography orediting effects have been applied. In fact, if you look up the MunkerWhiteillusion, you'll come across many more examples. Examine them in Photoshop and you cansee that the colors are the exact same. A similar effect can be seen with thischeckerboard illusion. Tile A clearly seems darker than tile B.But you know better by now, righté Even though your eyes can't see it, youknow when I removed the surrounding imagery the tiles will be the same color. Sowhat's going on hereé

The truth is that scientists don't fullyunderstand this phenomenon, and there are many complex biologicaland neurological factors taking place. Ultimately, our brains judge color andbrightness in context. In other words, our brains compare thesurrounding environment in order to create our perception. The purpose of our senses or eyes in this case, is not to provide us with an absolutecolor or physical property of our external reality, but to interpret what we see asefficiently as possible

in order to interact with theenvironment most appropriately. The tile illusion takes advantage of thisphenomenon. Our brains know that shadows makeobjects look darker, as a result the brain compensates byinterpreting the tile as being lighter than it appears until we take the shadow away. Perhaps, the most blatant example is this gradient. The middle bar is simply one color.

Remove the background gradient and itbecomes obvious. Once again, the darkness of the background hasaffected our perception of the bar's color. Our perception is relative. So do you still trust your eyesé Got a burning question you want answeredé Ask it in the comments, or on Facebook and Twitter and subscribe for more weekly sciencetutorials.

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