Here's an actual email I received concerning the level of grain in volleyball pictures shot at 6400 ISO.
Email question:
I am fairly pleased with my photos from [the] volleyball tournament. I am getting good stop action, but why are they so grainy?
I used my big lens (F4.0) and an ISO of 6400.
Any suggestions before we go to the next one?
Email answer:
The reason you have grain (or noise) is because you're shooting at 6400 ISO. Of course the higher the ISO, the better you're able to stop the action with good shutter speeds (due to better light gathering capability at high ISO). The downside is that high ISO increases the noise in your photos. Some cameras have better high ISO noise performance than others. All cameras introduce noise, however, as the ISO increases. For me, it's much better to capture a grainy photos than no photo at all. Here's one of my blog posts about this problem here:
http://www.lensextender.com/
To help solve this problem for me, I recently purchased a new Nikon body, the D700. It's got really good high ISO performance (supposedly the Canon 7D is really good as well). [This] attached volleyball shot was taken at ISO 6400 with my D700 and an f/2.8 lens.
You can also buy noise reduction software that works really well. Sometimes I use Noise Ninja for this.
