You might find this interesting. I basically turned off all the lights except one last night (in the house) and with the f1.4 Sigma lens shot at 26,000 ASA. I’ll be honest with you: I’m not actually sure what this thing goes up to. I set it at high, turned off Highlight Priority – and put it in AV mode and the most I could squeeze out of it was 26,000 (as if that’s not enough).
My normal shooting speed, going back to the days of film, was / is 400 ASA. So let’s see how many stops I’ve added: 400, 800, 1600, 3200, 6400, 12800, 25,600. That’s an extra 6 stops! (Yeah, that needs an exclamation point).
Now you probably want to know if it’s usable at that speed. Sure it is. In the examples below, the first shot straight from the camera, though I had High ISO Noise Reduction set to Standard. There are five levels there… from turned off to super-duper NR. That’s something to fool with.
Anyway – as far as my workflow goes: I took the RAW file into Lightroom (4.x) and using NIK Dfine I did my best to get rid of noise while still holding on to sharpness. I would say that you can get somewhere that resembles 400 film pushed to 1600. It’s not the same, and I can’t say that it’s better or worse. Just different.
Then I went into NIK Color Effex and later Silver Effex – and played around as if I were going to try and make an actual image with the processing.