I had read that my Canon 50mm f/1.4 lens has noticeable chromatic aberration (CA) when wide open, but was really surprised how bad it was, and how it almost entirely goes away at f/1.6.
I really love this lens - this is a minor problem to deal with, but it's nice to know to expect it.
Below are crops from two out-of-focus shots I took while driving: the first at f/1.4, the second at f/1.6. Notice the purple fringing around most of the lights at f/1.4. This is caused by different wavelengths refracting differently through the glass. I put up a full shot at f/1.4 on Flickr, here.
|50mm f/1.4||50mm f/1.6|