Originally posted by Winder
The Sigma is simply an excellent lens. It really does handle skin tones and bokeh very well. Its razor sharp even at F/2. At F/1.4 is does have some softness, but for skin and portraits its still more than sharp enough. F/1.4 and an 85mm has its own challenges, but the K-3 does a much better job than the K-5 with fast glass. I shot an event tonight with my K-3 and Sigma 85mm. Lived all night at F/2.8 at 3200 ISO.
Using the 85mm at close range at f1.4 gives you a razor thin focal plane, such that if the pupil is in focus, the nose or even the eyebrows will be out of focus. But used at a distance, f1.4 can be surprisingly useful, as can be seen in the following pictures of one of my dad's cars he owned when he was in his 20's (a Cord Sportsman 8/10).
To get the car to fill the frame, I was standing some distance away (maybe 40-50 feet?). And even though the subject is filling the frame, and I'm at f1.4, it's surprising how well the entire car is captured. Much of the car is actually out of focus, but the fall-off is gradual enough that it still works. I certainly could have stopped down, but I wanted to blur the background a bit, but it was kind of difficult since the airplane is was so close to the car (the back of the car is actually under the wing).
Please note that the picture was taken at midday in full sunlight, so the lighting was not the best, but thanks to the superb optics of the Sigma 85mm and the excellent dynamic range of the K-30, the picture was still very usable, despite the overly bright and harsh lighting. We drove halfway across the country so my dad could visit his old car, so this was the only chance I would have for photographs, so I was fortunate to have such capable gear! A sunset picture would have been nice, but we had to get back on the road before then.