Look at this interesting explainer on eye charts and human visual acuity

A Snellen chart (below) may just look like random letters in different sizes, but they were carefully designed to measure visual acuity. This piece on testing the limits of human vision brings it all into focus. Read the rest

Your perception of this graph is a graph of your perception

Look at the above image. The higher the peaks, the more sensitive your eyes are to contrasts at those frequencies. Ian Goodfellow spotted the image in a scientific paper about spatial frequency analysis and brilliantly observed that "It's like a graph that is made by perceiving the graph itself." Over at Mind Hacks, Tom Stafford explains the science of spatial frequency, the same concept behind the classic "Marilyn Einstein" image below that was created by Aude Oliva in 2007. From Mind Hacks:

Spatial frequency means how often things change in space. High spatial frequency changes means lots of small detail. Spatial frequency is surprisingly important to our visual system – lots of basic features of the visual world, like orientation or motion, are processed first according to which spatial frequency the information is available at...

Spatial frequency is also why, when you’re flying over the ocean, you can see waves which appear not to move. Although your vision is sensitive enough to see the wave, the motion sensitive part of your visual system isn’t as good at the fine spatial frequencies – which creates a natural illusion of static waves.

See Einstein below? Now go a few steps back from your screen and look again:

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Mark Mothersbaugh from DEVO has a line of rad eyeglasses

DEVO's Mark Mothersbaugh has a line of fantastic spectacles for booji boys and girls. Guaranteed to help you stay focused on the smart patrol! Here's Mothersbaugh on how eyeglasses improved his vision, and his life:

I have a really bad astigmatism and extreme myopia. I could see just enough to make it around a room but kids would throw a ball, and it would hit me in the head. I was happy and just kept running around because I didn’t know that I was any different than anybody else. The teachers at school would ask me to read the board and I’d say, ‘What’s a board?’” and they’d put me in the corner. Finally they tested me, and it was like “Oh my God, he can’t see the big ‘E’ on an eye chart from 12 inches away.

So, I got glasses right before my eighth birthday, and in the car on the way home I remember seeing clouds and trees. I had never seen what the top of a tree looked like. I had never seen a roof of a house. I was stunned and excited. The next day, I was drawing pictures. I remember the teacher who had been totally frustrated with me and disciplining me every day said, “Mark, you draw trees better than me.” That was the first time a teacher had ever said anything nice. I was struck by it, because I had never had a teacher say anything positive to me in my life. And I remember that that night, I went home and had a dream that I was going to be an artist.

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How prosthetic eyes are made

"If only you could see what I've seen with your eyes."

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Why does long-term zero-g hurt astronauts' eyes? Mystery solved

Turns out that long stints in outer space affect levels of cerebrospinal fluid. That explains why many astronauts who had 20/20 vision before space missions needed glasses upon return, according to a paper presented this week. Read the rest

Popular design guides are responsible for plague of grey type

A series of recent, influential design books and articles have convinced the web's designers to go for grey-on-white type, despite the fact that many people can't read low-contrast type (and it's even worse on mobile devices, which are often read in very bright sun, on screens that have been dimmed to save battery) Read the rest

Man blind since birth asked if he knows what he looks like

Tommy Edison, the very funny "Blind Film Critic," who has been without sight since birth, answers the question: "Does it bother you that you don't know what you look like?"

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Cool video demonstration of change blindness

Who will be the first to say, "I saw the changes right away. I don't understand why anyone wouldn't be able to." Read the rest

What happens when you look at the sun through a telescope

TV astronomer and author Mark Thompson uses a pig eye he got from his local butcher to demonstrate what happens to people who make the mistake of looking at the sun through a telescope. Read the rest

The woman who can see 100 times more colors than you can

Concetta Antico, who made the paintings above and below, is an artist known for being a tetrachromat, meaning a genetic difference in her eyes enables her to see approximately 100 times more colors than an average person. "I see colors you cannot perceive or imagine," Antico says. (Previous BB posts about Antico here and here.)

While the vast majority of peoples' eyes contain three kinds of cone sensitive to different wavelengths of light, tetrachromats have four. Apparently the genetic difference isn't very rare, but only a tiny fraction of those who have it actually develop unique perception. Why? UC Irvine researcher Kimberly Jameson and University of Nevada's Alissa Winkler studied Antico, another tetrachromat, and an artist with regular vision. From David Robson's article at BBC Future:

The experiment tested the participants’ sensitivity to different levels of "luminance! at certain wavelengths of light; put simply, with Antico’s eye’s extra cone, she should be picking up more light, meaning that she could see very subtle differences in the brightness of certain shades. Sure enough, Antico proved to be more sensitive than the average person, particularly when looking at reddish tones – a finding that perfectly matched the predictions from her genetic test.

As Jameson had suspected, Antico also performed much better than the other potential tetrachromat who was not an artist – supporting the idea that her colour training had been crucial for the development of her abilities.

Using these results, Jameson then reconstructed some photos to give us a better idea of the way the world may look to Antico.

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Blindsight: weird phenomenon deepens the mystery of consciousness

Blindsight is a strange phenomenon that sometimes occurs when people have lost sight due to visual cortex damage but still respond to visual stimuli outside of their conscious awareness. New research into blindsight is offering clues, and even more riddles, about how we can "pay attention" outside of what we historically have considered conscious thought. From David Robson's fascinating article in BBC Future:

One of the first tasks (in a recent research effort) was to test exactly what blindsight patients are capable of without their conscious visual awareness – and the results have been quite remarkable. Of particular interest has been the fact that they can sense emotion: when presented with faces, they can tell whether it is happy or sad, angry or surprised, and they even start to unconsciously mimic the expressions. “Even though they did not report anything at a conscious level, we could show a change in attitude, a synchronisation of emotional expressions to the pictures in their blind field,” says (Tilburg University scientist Marco) Tamietto...

Besides mirroring expressions, they also show physiological signs of stress when they see a picture of a frightened face...

In 2008, Tamietto and (blindsight research pioneer Lawrence) Weiskrantz’s team put another blindsight patient through the most gruelling test yet... He was blind across the whole of his visual field, and normally walked with a white cane. But the team took away his cane and then loaded a corridor with furniture that might potentially trip him up, before asking him make his way to the other side.

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This trippy GIF reveals patterns each time you blink

Take a quick tour of how your brain processes patterns by blinking at different speeds while looking at this GIF. You'll probably see concentric circles appearing in different places, and possibly pentagonal lines now and then. Read the rest

Real-life eyeshine surgery trial

In the Chronicles of Riddick series, a shiner is an outlaw who has undergone eyeshine surgery to give them night vision. That same thing, incredibly, is happening in a garage in a small town in central California: Science for the Masses is a group of biohackers who have successfully tested a procedure giving its brave/foolish test subject the ability to detect shapes in a no-light environment. Read the rest

XKCD reveals your visual perception quirks

Today's XKCD, "Visual Field," is a terrific mind-bender: a series of optical experiments to try with your computer's screen and a rolled-up piece of paper that demonstrate the quirks of your visual field: your blind-spots, your ability to perceive detail, night vision, the ability to perceive polarization, sprites and floaters, color perception and so on.

Visual Field Read the rest