it is....hmmmm i'll let you know I have a few other things i've been offered, im considering this because the 20 3.5 I was offered isn't AI'd and your 20/4 would work seamlessly on my FG.
Yeah I had a Canon 20-35 for my EOS system that I loved dearly but the coatings suffered a huge nick on the front element from vibrations in my car, sold it on here for 40 bucks. Lesson learned, use UV filters or put the caps on your lenses.