I can't tell you how many times I've heard the desire for good High ISO Performance referred to as a religion. Is it? No. Plain and simple, we as photographers, as creatives, want the best image quality we can possibly get. That’s not a bad thing, and digital noise does have a number of negative impacts on a shot, from loss of detail, to color and contrast issues.
The shot above, of Heart guitarist Nancy Wilson, was shot at ISO 2000, 24 mm, f/4, 1/500. I needed a fast shutter to freeze Nancy’s hair, and I was already wide open on the Canon 24-105 f/4, so the ISO was sacrificed. Oh yeah, the drummer is Jason Bonham.
If you shoot photos at high ISO, you've seen noise. And, if you shoot at really high ISO, like 3200, 6400, or higher, you've been disappointed when what could've been a great shot becomes just okay (again, depending on the camera). For many people, that means avoiding high ISO at all costs, but does noise really matter, and if so, is it ever OK?
As I mentioned, I shoot with a Canon 7D. Images shot at ISO 1600 on my camera do have noise, yet I shoot at that setting far more than I shoot at 100 - 400. I often shoot at ISO 3200 - and on occasion I even hit 6400! At 100% zoom (which is often recommended for accurate noise reduction) those images definitely have noise. Still, I do it. Why would I choose to shoot at such a high ISO knowing it will produce noisy images?
Photography is an art of compromise, and in live music photography your choices limited. Concerts can be one of the most difficult lighting situations you will ever face - fast moving performers, fast changing low light, and extreme dynamic range. Your choices are: A) Take a blurry shot of a fast moving artist, or a hair whip; B) Crank the ISO to get a shutter speed fast enough to get a sharp shot
You should always choose B, because a sharp noisy shot is always better than a blurry clean shot. There are tools to deal with noise in post production (Rick reommends Topaz DeNoise), but a blurry shot is always blurry. I will use a touch of noise reduction in Lightroom when needed, and on a rare occasion I will pull out Nik Define - which I almost always apply selectively using the brush feature, or masks. (Rick also and always recommends working selectively.)