Actually both have identical optics, and they are not IF (the Canon is). One
advantage of the FA is better manual focus ring as the F has a very narrow
one. The new D-FA which is much lighter and smaller, is just around the
corner so it might be a good idea to wait. I suspect the new one has the
same optics but with triple plastic barrel instead of double metal on the
F/FA.
Alan Chan
http://www.pbase.com/wlachan
The optical formula and mechanics are different.
I don't have the FA or F, but I believe both use internal focus mechanisms.
Theses lenses don't change length as you focus.
I am not sure if there is much difference in image quality.
I'd be interested in any comparisons.
