Hot Spots In Eyes

Why Do We Have Blind Spots

We're going to do a little experiment. Make sure you watch this part of the tutorialin full screen. Close or cover your left eye, look at theplus sign. Be aware of the circle, but don't focus on it! Keep looking at the plus. You may need to move your head back and fortha little bit, or move your thing closer to your face. But at some point, the circle isgoing to disappear. Now close your right eye and look at the circle.Move your head back and forth until the plus sign disappears.

You've just found your naturally occurringblind spot in each eye. And of course daily practice we do not notice this. The human eye has what you might call a fundamentalflaw. Lightsensing cells in your retina send signals to your brain via nerves. And thosenerves are in front of the lightsensing cells. Eventually, those nerves have to pass throughthe back of your eye to get to your brain and in the part of your retina where theypass through, there aren't any lightsensing cells. That's your blind spot. Now this isn't normally a problem, becausethe blind spots are located at slightly different

points in each eye, and each of your eyeswork together to fill in a complete picture. But even with one eye closed, you're notseeing a big black hole. Instead, your brain fills in what it figures ought to be there.That's why, when the circle disappears, you see the color of the background. Yourbrain is guessing, and it's guessing wrong. Although! At least one very small study foundthat you might be able to shrink your blind spot with practice. Researchers showed ten participants an imagethat fell within the margins of their blind spots and asked them to describe it. By theend of the experiment, people got a little

better at describing those images. The researchers think it's because the lightsensingcells right around the edges of the blind spots became more sensitivebetter at pickingup and passing on light signals. That's the kind of skill that's probablynot going to ever make any kind of difference in a lifeordeath situation, and humans havehad blind spots in their eyes for as long as we've had eyes. But it's a neat wayto try and hone your brain, if you're into that sort of thing. There is a different kind of creature, though,that just completely avoids this problem.

Cephalopods, like octopuses and squids, havetheir nerves behind their lightsensing cells, so there's no need for them to have a blindspot. Why did we not do it that wayé Evolution.Well I, for one, welcome our tentacled overlords. Thank you for asking, and thank you especiallyto all of our patrons on Patreon who keep these answers coming. If you'd like to submitquestions to be answered, or get these Quick Questions a few days before everyone else,you can go to patreon scishow. And if you just want to keep getting smarter withus, you can go to scishow and subscribe! Just do it.

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

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