My current camera is a Canon 5D Mark 2 which claims a maximum ISO of 25600 on paper, but in reality a maximum ISO of 6400 is suggested by Canon. Even so my previous high ISO experiences have meant I've limited myself to 3200 ISO when shooting in low light conditions such as at music gigs.
The photo above was a quick test I did to see what 6400 ISO actually looks like and I'm really happy with the results. The image looks more like the results I used to expect at 800 ISO on my Canon 40D. Click the image to zoom in and see for yourself.
The lighting was supplied by one very small candle which gave an exposure on the face of just 1/15th sec, f/4 ISO 6400. The lens was a Canon 70-300 IS and the shot was hand held, yes the Canon’s I.S. system really is that good!
Impressive as the results are, there’s no getting away from the fact that high ISO shots need a bit of post processing to really control noise and for me nothing beats the new noise reduction features found in Photoshop CS5 or Lightroom 3.
Not surprisingly I’m going to class 6400 ISO as a usable setting for the 5D mark2 from now on.