I was going to post this under my Nocti question ... but after testing the Nocti f/1 in really crappy light, I had a few thoughts to share:
I've done some home snap shot tests in low-light, and the focusing on this specific Nocti is spot on @ f/1 where it will be used 99.99% of the time. It's not 6 bit coded, but manually setting it in the menu is a no brainer. So, if it ain't broke, I ain't gonna fix it
Processed a couple of shots in LR and C1 ... like the 24/1.4 ASPH this lens fares better in C1 where purple fringing around specular highlights is easy to correct. The attached candle shots comparison demonstrates that ... it took 19 minutes of screwing around in LR to get the flame edges even close to C1 with a one button click.
I also did some sequences ranging from ISO 1000 through 2500 ... every shot was usable ... 2500 will make a fine 8X10 which is about what I need for 99.99% of printed wedding shots. This was in dark conditions and weak Tungsten lighting from one lamp and some twinkle lights. So dark that the Nocti at f/1 with ISO 2500 gave me a shutter speed of 1/30th.
I highly recommend manually setting WB in these types of lighting conditions. WB affects actual exposure once WB is corrected and Tungsten contaminated shots can fool you into thinking they are properly exposed when they are not. Auto WB just can't handle color temps this warm.
The over-all room shot was @ ISO 1000. which is VERY usable even for larger prints. I think it is as good as 640 was on the M8 given the same print sizes as comparison.
Oh, and while the Nocti typically vignettes, the vignette control in C1 fixes that IF you want it fixed (most of the time I don't and actually like it for wedding photos.
Here's some happy snaps I did for these tests: