Sigma 180/2.8

for me the quality of olympus lens is the best both image quality and built quality if there is a problem, is the speed of the AF is bit slow compare to other brand. in this case, i do have sigma 150mm f2.8 and it is sharp lens but i don't really like with the color tone produce with this lens.. it is slightly "yellowish" i guess.. and for once i had tried ZD 150mm f2 and it is the sharpest lens among other ZD lens.. me myself want to get one next year.. and btw the existence of sigma 150 f2.8 is vary vary rare now, if you really find one in new condition you better take it.. i never consider sigma lens in second hand condition because the built quality is not as good as ZD lens

cheers
arief