Eli5: Why are super close-up images black and white, or weird colors?

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Anytime I see an image of say a tardigrade or a dust mite, it’s always greyscale, and when I see one of those videos that zooms in closer and closer to say a toothbrush, it always shows weird colors before it gets atomic. Can we just not see color past a certain scale?

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Anonymous 0 Comments

> Can we just not see color past a certain scale?

Basically, yes.

A specific colour – at least, the ones on the rainbow – is defined as light with a specific wavelength. Or frequency, but you can convert between them.

The problem is as you get into smaller and smaller sizes, those wavelengths start to become a problem. “Bluray” discs for movies and video games are so-called because in order to make the holes on the disc smaller, the laser needed to be a new colour… yes, blue. CD-ROMs are infrared, DVDs use a red colour closer to what people imagine red lasers are like, and Bluray are of course blue. Blue has a smaller wavelength than red.

You might see where this is going. As you get smaller and smaller, colour doesn’t mean anything any more. You can’t measure colours because you can’t get light of a wavelength to bounce off the thing and see what reflects back and what doesn’t. The tiniest things use electron microscopes which, as the name implies, uses electrons instead of light to “see”. There’s no colour here. Even getting 3d-looking images out of an electron microscope took effort.

Anonymous 0 Comments

Small invertebrates like this [tardigrade](https://i.imgur.com/635ZaGu.jpeg) seen under an optical microscope are mostly transparent.

What you refer to are images created with an electron microscope (using, well, electrons in a vacuum and not light), which only produce shades of grey and not colors.

But the result can of course be digitally colorized afterwards like this other [tardigrade](https://i.imgur.com/yssbCSy.jpeg).

> Can we just not see color past a certain scale?

In a way. With light you can only resolve details up to the light’s wavelength, i. e. ~ half a micrometer. Hence the use of electron microscopes to peer at smaller things.