Originally posted by Wheatfield It's the glass.
However, any decent raw converter has a CA adjustment built in, so there is no reason to tolerate it.
I've heard this many times but I have close to zero luck in correcting CA with Lightroom. I've played with the sliders and
occasionally it helps a little, but rarely. Most of the time, it does nothing. Defringing occasionally helps with controlling PF, but it can't compete with the purple you get out of the 10-17mm fisheye, for example. If there's some magic "fix CA" button that I've been missing, I'd sure love to hear about it!
If it gets really bothersome, I will often use an adjustment brush and drop saturation on the edges, this effectively turns the color from purple to gray, which is a lot less distracting since most examples of PF will happen with an almost white edge next to an almost black edge.