[mst]

This post talks about (see the end) a new "ring-shaped flare", due to the very specific design of the lens:

Interesting. I wonder if this also is a problem with Canon DO lenses... I once owned the 70-300 DO, but don't remember anything like this in my shots... but I rarely shoot at night anyway.

But I remember that the 400 DO was said to have a little less bokeh quality than the other "great whites" due to the character of the DO element.

-- Markus