the tamron len is way much better than sigma, unless someone hv tried the new 105mm DG sigma? Di is good if yr using dynax bodies with the D function. I am looking forward in getting one myself, only the one with Di. $650 i think? 28-200? they say at 28mm is OK if u shoot around F8? who knows very has their own stories about 28-200mm lens. my friend brought one (nikon) not bad he said.