Chromatic Aberration

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I've always wanted to know why some colours "vibrate" next to each other. I did some digging and it's actually the same reason good camera lenses are so expensive. 👇

There are two related visual effects happening here and they both have insane names: - Axial Chromatic Aberration - causing the vibration - Chromostereopsis - causing the weird 3D effect

You've probably heard of chromatic aberration before: Essentially, each wavelength of light (colour) has a slightly different focal length within your eye. In this case red has a shorter focal length than blue.

This is what causes the "vibration" - your eye struggles to focus on the border between the two because they literally can't both be in focus at the same time. It also causes that halo effect as your eyes blur the two colours together.

Chromostereopsis is when this focal length difference is opposite in each eye and it creates the impression of depth. This is why that red donut appears closer to your eye than blue background.

Trippy optical illusions, like this, layer these effects to make it appear like parts of the image are actually moving.

So what does this have to do with camera lenses? Well, chromatic aberration affects cameras too as light is dispersed through glass in a similar way to the lenses in our eyes.

Lens manufacturers reduce it by adding extra elements and special low dispersion glass to focus the wavelengths at the same point. This glass is doped with all sorts of chemicals that change the way light refracts through it. Obviously, this is expensive.

It's very difficult to do this in zoom lenses, where the focal length changes all the time. That's why they end up looking like this inside and costing $$$$.

These days a lot of chromatic aberration correction happens in software, especially on smart phones. Just another way in which digital images are made up. twitter.com/DanHollick/status/1491436859238412288?s=20&t=ZJ8hTVxhr5N7mks8N9HrvA

Fun photography fact for anyone who made it down here. The way we describe aperture (f/2.8) is actually an equation where f equals the focal length of the lens. Aperture diameter = f(50mm)/2.8 = 17.85mm