SaladMonster

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wobblegong
@wobblegong

There is a widespread meme about "shrimp colors" which hinges on the idea that mantis shimp can see way more colors than us. It turns out this is not true! Mantis shrimp can see ehhh wigglehand, roughly as many colors as humans can.

However, figuring this out required some very interesting science into the mechanics of seeing color, and it paths into the resolution of a second animal-vision myth: cuttlefish are not colorblind, and the explanation for that is even cooler.

Super tl;dr: human vision uses three types of color receptors and make your brain do math to average them out. Mantis shrimp have twelve types of color receptors but don't brain-math so they see slightly fewer colors faster. Cuttlefish don't have color receptors at all and instead use the physics of light refraction (prisms!) to figure out its wavelengths, ie color.


lmichet
@lmichet
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in reply to @wobblegong's post:

yeah the article clarifies that it's not about time delay of arrival; chromatic aberration like that isn't detectable in timescale biologically, but it changes the focal point of each frequency.

so objects of singular color wavelength will be in perfect focus at some focal length that is a function of distance and wavelength, and by sampling sweeps of focal length we can synthesize true color in a continuous spectrum rather than K filtered bands without ever eliminating incoming light

i think the "synthesis into a focused and useful full-spectrum image" is the really hard part here. seems understudied.

it seems like kind of fortunate that human eyes don't work like this, otherwise every mode of photography and image reproduction we've ever invented would look like dogshit lol

no problem! thanks :eggbug-smile-hearts:

anyway yeah TECHNICALLY chromatic aberration is a time delay, or an artifact of time delay. but the main thing you can actually detect is that when different wavelengths of light are slowed down by different amounts in a material, they refract by correspondingly different amounts (that's how lenses work after all, and why strong modern eyeglasses are less thick than they used to be: we've gotten much better at making materials that light goes really slow through).

Correct! I didn't want to get sidetracked looking up/explaining their greater wavelength range (you may notice this post is already a bit long 🤣) but like quite a lot of animals they can see more of the spectrum than Homo sapiens.

Alas for the "shrimp colors" joke, nothing I've seen suggests this increased range is especially big. The terminology I usually see thrown around is "near" infrared/ultraviolet, to indicate it is in the IR/UV range but fairly adjacent to our rainbow. If you look up a chart contextualizing the Homo sapiens visible spectrum against all wavelengths, you will notice we see only the tiniest sliver of what exists! Birds, mantis shrimp, etc can see a bit higher/lower on the spectrum, but it's only a bit. They are probably getting closer to 1.1x our color range than 2x.

(Caveat: since it already takes a lot of cleverness and determination to figure out what animals can see of our spectrum, testing their UV/IR limits is probably trickier. It's possible nobody's done the science at all! We may legitimately not have an answer here.)