Bought a used lens here not long ago. Figured it would be worth messing around with. Aperture blades stick randomly. Went out and shot with it one day and it drove me nuts. Sent to CRIS, and the estimate is $169. I've already got $100 in it. So, $269 doesn't seem worth it compared to what I've seen working units selling for. If I can get my $100 back out of it, I'm wondering what is comparable in IQ? I had thought about a Canon 10-18mm. But, will I miss the speed of this prime? Especially in 100% working order.