i am a proud owner of tokina 11-16

i tried both sigma 10-20 & tokina 11-16 before buying. both lenses (for me) has the similar built quality - sigma is smaller & tokina is bigger. sigma's zoom ring is smoother, while tokina's rings are tougher. sigma gives free pouch while tokina gives free lens hood. sigma has the built-in AF motor which can AF in my D40. but i ended buying the tokina 11-16 for it constant aperture @ f2.8.

i am enjoying manual focus with this lens, as much as i enjoy MF with the 50mm f1.8

the widest @ 10mm vs 11mm is not really big different, it's just a step (or two) backward to get the wider view. although most of the times i use this lens for outdoor shooting, but i shoot a lot with this lens indoor as well, so it's wide aperture is really helpful especially in tricky/dark condition.

the latest fun i found from this lens is, it can create "the dog" effect - big head small body. i.e. shooting a person (half squad) on top of his head while he's looking up & funny pose. set the aperture smaller (higher f-number) so that the whole body is in focus. the end result is the head is bigger than the whole body as if it was photoshop-ed!!