Upload & Sell: Off
I used a nikon 70-200 vr1 for years on a d300 and d700. Now I have a sigma 70-200 OS on my sony a850. I know itīs not a direct comparison, but anyway...
Focus speed seems plain slow to me compared to the old nikon and Iīm not only talking about how fast it locks (I guess that has sth to do with the camera) but also how fast the hsm moves through the scale. I wouldnīt call it fast at all. To compare a bit more, I also find the old nikon 80-200 AF-D faster on a d300.
Optically itīs not bad, near 200 itīs a bit soft, and itīs not 200 either. If you compare it to a minolta 200 2.8 HS the sigma is shorter in focal lenght, has worse bokeh (not by much) and low contrast in comparison. CA is neck and neck and depends a lot on the lightning. Itīs curious how much I liked the nikon 70-200 on the d700, and how little I like this sigma... itīs not that itīs a bad lens, but it has no soul... it sounds a bit stupid, but I see the pics I take and they look a bit flat, donīt know how to explain it; technicly good, but without character.
Apart from that, this weekend, while shooting a wedding, I was running to cross the street with my sony and sigma in my hand, when the screws that join the mount to the rest of the lens broke down, so the mount stayed on the camera and the lens hit the floor heavily.... I took a closer look, and found that those metalic screws plug on to a plastic piece, so the plastic thread was literally ripped of and then, the body came appart from the mount itself...
To sum up: Itīs a good lens, technicly good, but I prefer my nikon 70-200 vr1, the only situation where I prefer the sigma is while shooting landscapes, and even then... if I were shooting nikon, I would buy the nikon if I could.