Why is chromatic aberration purple?

[Evelyna42]

Just a silly question that I'm wondering about at the moment. Why is chromatic aberration purple? Well, usually purple anyway. I guess I'm interested in the mechanics of it and can't seem to locate an answer. I understand why chromatic aberrations occur thanks to this article: https://www.photographytalk.com/chromatic-aberration-and-how-to-fix-it-in-photoshop-or-lightroom but it doesn't explain why they're purple.

Just wondering...not a crisis

[VisualEcho]

That's a good question. But in my experience CA is not only purple, it's magenta, orange, green, and cyan. I'm a shallow DOF whore, and pretty much all I use is 1.4 to 2.2, so I have to deal with CA a lot, and it's definitely different colors.

I believe the reason is that light has a spectrum of colors that when mixed properly aren't always able to seen, and it's literally the bending of this light by the lens (like a prism in sunlight) that causes the colors to split apart. It's a sharp bend, a sharp contrast, so the colors are sharp. At least that's what I've understood over the years.

I'll also say that my 200/2 is my favorite lens, I shoot it exclusively at f2 has almost no CA, which is fantastic. Really, it blows every other lens away in that regard, and in most others.

[overcoil]

Purple Fringing is probably the term you should use to research the phenomena.