Chromatic Aberration

Purple and green where it does not belong

One of the lens imperfections that effects corners on bright spots

What is this

Also known as Spherochromatism, chromatic aberration basically arises when different wavelengths of light (i.e. colors) are modified slightly differently by the lenses and the colors are focussed slightly differently on the image sensor. This shows itself usually as purple and green shadows around brightly lit edges.

Unlike most other issues with lenses, this is quite tricky to correct in post processing. It is also quite a challenge to get this perfect when designing a lens (especially longer/faster lenses suffer more).

Fortunately for everyone, this issue is only visible in extreme conditions for a reasonably good lens. The physics and the remedies that lens designers have are actually quite complicated (i.e. I have no idea what they are), but one thing that sometimes helps is to use a smaller aperture. And stay away from sharp color transitions on a blurred bright background.

Here is the issue

I came across this one by chance. It was taken using a Nikon 135 at f/3.2 on a Nikon D500 all of which are top of the line equipment actually. This is not a great shot, the idea was to focus on the house, but the focus is on the branches.

If you look closer to the center left, it is very ugly. The branch in the middle is completely purple and there are flashes of purple and green everywhere. This is as bad as it can get for a modern lens.

These pages are for Amateur Photographers and not really for seasoned photographers and professionals. I have no affiliation or commercial interest with any brand/make. I write from my own experience. I ended up using mainly Nikon, so I am more familiar with this brand than others. See price for notes on pricing as well as photography related links.