Noise Reduction in Camera Raw
Camera Raw includes two sliders for reducing Luminance and Colour noise under the Detail tab. Colour noise is the more obtrusive, which is why the default Color slider value for raw files is 25, while the default Luminance slider setting is 0.
You’ll find that the default Color setting does a good job, and you won’t see much difference if you increase the value.
You can try increasing the Luminance value, but because the luminance noise is less tonally distinct than colour noise in relation to adjacent pixels, you’re more likely to blur detail.
You may find that with the colour noise reduced, the grainy effect of the luminance noise is more palatable than the softening effect getting rid of it can produce.
A new noise algorithm was introduced in Adobe Camera Raw 6 and Lightroom 3 that retains an impressive level of detail when removing noise, plus an option to add ‘film grain’.