Hi peeps. I rarely post here but noticed that there's a thread for this lens and not many people own it, so I thought to chime in a bit.
I shoot a D700, and when I travel, the only lens I bring is the 28mm 1.8G, which is a GREAT lens. I own the 50 and 85 1.8G too, so I am an exclusively prime guy. The 50 sees extremely little use. The 85 is rarely used, but I am never gonna sell it because when it's used, it's just beautiful.
When this lens came out, Sigma seem to have brought me my perfect dream lens! Sure, wider a bit, longer a bit, might have been better. But if it meant image quality compromise, prime user like me wouldn't even be interested! I understand though I belong to the extreme minority who purposely limit myself to an extremely narrow focal range so yeah

Sold the 28 and 50 for this.
Anyway, regarding the lens, it's beautiful, and heavy. But it balances well on D700, honestly, very much unlike the monster Tamron 15-30 which I tried. That thing made my arm sore after 30 mins of use. Focusing using the center point on mine is accurate (or accurate enough), and sharpness is incredible edge to edge. Now the bad thing, the focus misses a lot when you use the off-center non cross-type AF point, so unless your DoF is extremely shallow, focus and recompose using the center AF is gonna be better. Does anyone know if this is something Sigma can calibrate? Focus is only bad at the non center point?
Haven't used it much but you can judge the quality with the two pictures I took few days ago. Ask me anything regarding the lens!
Pearl Centre Singapore by
khipin, on Flickr
Red by
khipin, on Flickr
PS: Bought from Parisilk @ Holland V for $1190 in case anyone wanna know the current price. Local set.