Sigma 180mm F/3.5 EX DG HSM APO IF Macro
Nikon 50mm F/1.8D
This is a photo I took to test out the new AF system on the D800. The shot was taken in complete darkness. It was as dark as it was going to get that day, and no lights were on inside the truck. I could barely see to set the AF point.
This is the same shot, only bumped up by 4++ stops in ACR 6.9.
You can see that, even in such low light conditions, the focus on the shot was spot-on. There's some horrible quality loss because of the exposure tweaking in post, but you can still tell it's focused on the eye.
A bit of noise reduction (for some reason, this brought the blacks down as well?), and spot exposure compensation on the eye, and, at normal viewing distance, you'd be hard pressed to tell that it was taken back so much. It's not the best quality image, for sure. But, try doing something of the sort with another, non-pro DSLR.
Feel free to leave your thoughts in the comments section!