Am I going blind?
August 7, 2010 1:07 AM   Subscribe

Am I going blind?

Why do red letters (on a computer monitor) flash and alternate between light and dark tones when placed against a blue background?

I've had this since I can remember, and always assumed it was just some human eye-function anomaly.

Here's a site as an example: (I promise I'm not advertising them! :)

Scroll down to the headline that says "You'll Benefit From Our Expertise". Does that look weird to anyone? Almost unreadable as it's over/under exposed?

If I focus on the actual letters, they appear a light whiteish-red. If I let my eyes focus into the distance behind the lettering, the letters turn a dark shade of red. Moving between these focal points adjusts the brightness accordingly. This seems to happen only when it's red/blue lettering.

I've tried searching, but can't find anything specific. Does this happen to anyone else? Or is it just a sign that I have some eye deficiency?

Thanks! (Not worried or anything, just curious, unless it's some precursor to my retina detaching....! :)
posted by coldblackice to Health & Fitness (15 answers total) 2 users marked this as a favorite
Yup, I have trouble reading it too. Crap website design.
posted by taff at 1:16 AM on August 7, 2010

Best answer: If it's the effect I think you mean, then I think that's a normal optical illusion— colors which are of similar brightness but far apart on the color wheel produce it. I don't know its name offhand. Is this image an example of the same effect you're talking about?
posted by hattifattener at 1:23 AM on August 7, 2010

Best answer: Chromosteropsis? More here.
posted by mdonley at 1:25 AM on August 7, 2010

"Scroll down to the headline that says "You'll Benefit From Our Expertise". Does that look weird to anyone? Almost unreadable as it's over/under exposed?"

Yeah, I'm having trouble focusing on the letters, it feels like they're almost swimming around compared to the black-on-blue text.
posted by Jacqueline at 2:20 AM on August 7, 2010

"Is this image an example of the same effect you're talking about?"

And THAT actually hurts my eyeballs to look at. Yuck!
posted by Jacqueline at 2:25 AM on August 7, 2010 [1 favorite]

Response by poster: Ahh! Yes! So I'm not going blind or insance :)

Thanks for the help guys
posted by coldblackice at 3:06 AM on August 7, 2010

Response by poster: ...*insane

It's 4:11AM

posted by coldblackice at 3:07 AM on August 7, 2010

Ouch, that makes me feel like my eyes are crossing when I look at it.
posted by frobozz at 5:04 AM on August 7, 2010

red and blue at similar/equal intensities force the rods (the cells in your eye which perceive color) to do all the work, with no help from the cones (which perceive light/dark). Vast oversimplification, but this is why you never do red on blue, orange on green, etc. for copy. I know some logos, especially athletic ones, break this rule, but you're not reading an american flag or a New England patriots logo for hours (or even minutes) at a time.

Odds are there's nothing wrong with your eyes. Of course, IANAED, and everyone should get checked periodically.
posted by randomkeystrike at 7:23 AM on August 7, 2010

its because red has a long wavelength and blue has a short wavelength in the color spectrum, put anything like them close together and you get an optical illusion effect.

In color theory classes i took in school, i learned why red is such a good color and blue is so bad for signage...

next time you see a blue sign, make note of how hard it is to make out at a distance, while a red sign at the same distance is pretty easy to read, its because of the reds wavelength travels further with less "distortion" while the blue get a jumbled up with itself.

same theory behind using a red light at night to keep night vision
posted by Mesach at 7:41 AM on August 7, 2010

You have it backwards, randomkeystrike. The cones see color, and the rods see black & white. Different colors refract at different angles--that is why a prism spreads out the spectrum. The lens in your eye is just a specialized form of prism that gets fatter or thinner to focus images on your retina. Your lens has to adjust its focus for frequencies that are as far apart as red (low frequency, long wavelength) and blue (high frequency, short wavelength), so when those colors are together you are constantly alternating your focus between them.
posted by weapons-grade pandemonium at 8:23 AM on August 7, 2010

Best answer: Many of the answers here start at what's going on, but it's a bit tricky. The retina is comprised of large, color-insensitive rods and small, color-sensitive cones. Light enters the eye and is focused by your cornea and lens to fall on the fovea - the part of your eye that is most densely packed with color-sensing cones. That's why whatever you're looking directly at in bright light is in the sharpest focus: cones are small, you can pack more of them in a smaller area, and therefore have a sharper, more detailed image.

Cones come in three types: red, green, or blue (sensitive to low-, medium-, and high-frequency wavelengths). Cones send off signals when they are activated by their particular wavelength of light. Red cones send off strong signals when there is a high intensity of red light, and send weak signals when there is a lower intensity of red light, etc. Cones perceive light and the signals they send to the brain provide information on color (in the form of which cone is firing) and brightness (in how strong the signal is). Good so far?

Things get tricky when we have the same luminance, or brightness, of different wavelengths. When we see red of brightness X and blue of brightness X, these two stimuli are at equiluminance. Weird stuff happens at equiluminance: what we normally see as a 3D rotating ball becomes flat, and the perceived speed of an object slows down. And web pages look crappy. At equiluminance we can't use contrast to help us discriminate edges so things are, quite literally, less visible.

(I am a vision scientist but I'm certainly no color expert - if anyone wants to provide more detail, please do!)

tl;dr: Two different colors at equal brightness are hard to see next to each other because of how our eyes and brain work.
posted by nicodine at 9:35 AM on August 7, 2010 [1 favorite]

tl;dr: Two different colors at equal brightness are hard to see next to each other because of how our eyes and brain work.

Is this an absolute rule? Because I have zero difficulty reading that portion of the text OP linked to, and try as I might, I see no "illusion" or effect of any kind - just ordinary letters on a perfectly readable background - may as well be black on white. I hope that doesn't mean I have brain damage, or a monkey brain or something.

Bottom line to the OP: FWIW, the text doesn't work for me as it does for you - one data point.
posted by VikingSword at 11:24 AM on August 7, 2010

Neither the text nor the heart bother me at all, but I've definitely been able to read things that other people have found eye-hurting so I just chalk it up to standard variation.
posted by wayland at 12:34 PM on August 7, 2010

One addition to nicodine's answer: your eyes also do not have a perfect distribution of the different cones; much of your perception of your visual surroundings is synthesized and computed in your visual system. Many of the optical illusions and other effects result from these systems.

As an example of what your brain is hiding from you, consider that there is huge variation among individuals in terms of what % of the restina is sensitive to what frequencies (and so on) -- .
posted by rr at 1:55 PM on August 8, 2010

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