This is truly one of my biggest hates when viewing a photographers work.
Have you ever taken a photo and seen those tiny little ghosty green or pink edges on certain detail, usually near over exposed edges like wedding ring diamons, shiny areas, leaves in the sky etc.
Well its an ABSOLUTE simple problem to fix...but some professional photographers don't even bother. Is that still professional?
What causes it? Well its a rather long and boring debate, but lets say this, a LOT of prime lenses do it, but with that said a lot of cheaper primes also do it. Now I'm not saying the expensive ones don't, even my Nikon 105mm 2.8 Macro and my Nikon 50mm 1.4G are major problem lenses when it comes to the chromatic ghost.
Cause aside...there's a way to fix it and your clients shouldnt have to receive images with lens design fault incorporated when you have the tools to fix it :)