Alright, here are the promised Sigma 50mm f1.4 samples. The subject is something of an unusual event since it was a trail lit by 700 jack o' lanterns carved by local schoolkids. That means I shot my Kx with the Sigma at f1.4 and ISO3200 with shutter speeds ranging from 1/15 to 1/350. Autofocusing worked surprisingly well under the conditions, and live view saved my bacon on a couple shots. Post-processing in Aperture was extremely minimal. I don't feel as though there was much to fiddle with in terms of NR, sharpness, or contrast.
Flickr - 2011 Great Pumpkin Walk, Canandaigua, NY