I'm thinking it's time I got a fast short zoom.
I'm kinda tossing up between the Sigma and the Tamron but haven't ruled out the pentax.
I guess what I'm asking is for some input as to wether the Sigma (18-50 2.8) is worth the extra $$ then the Tamron 18-50 2.8, or for that matter the extra $500ish for the pentax??
what are your experiences? the good the bad and the ugly.