Beau Hooker , Jan 12, 2005; 08:36 a.m.
Hi Nick, I think the *best* way is to download a copy of NeatImage or Noise Ninja - I believe they have evaluation copies. They can do truly amazing things. If you want to stick with Photoshop, here are a couple of suggestions:
1) Identify the channel that has the most noise and either use gaussian blur or one of the noise filters (like dust and scratches) to blur that one channel. Many times the noisest channel is the blue channel, but not always. This is usually preferable to blurring all three channels
2) I've had mixed results with this method but you can try it: Convert your image to Lab Color Mode (Image>Convert to profile>Lab Color) Apply a gaussian blur to the A and B channels (try 1.5 pixels to start) Be sure to leave the Luminosity channel alone. Convert back to RGB.
Again, nothing that I'm aware of in Photoshop can touch NeatImage. Give it a look. Good luck!