I just bought a Sigma lens from a shop and I told my friend about it. He asked me :"Did you test the lens on the spot?" I say "No, cause I dun have my cam body with me!" then He said "You should because Sigma's QC is terrible one!....." I then call 2 more of my friends, whom have about 5 and 10 years photography experience, and they re-iterated what the 1st guy said. Wah kaozzz! I should have asked them for opinion first before heading down to buy the Sigma lens. But anyway, how do you test a lens "on-the-spot" in a shop? Firstly, you need your cam body and then a PC to view the downloaded photo and furthermore you need to bring the lens out of the building to take test shot, if not you cannot actually "test" a lens right?