types of noise

hi there. In my seemingly endless attempts to understand my camera, i came across two type of noise: luminance and chominance.

i read in a different forum from a poster this description:

The luminance noise is when pixels show different brightness but are of the same colour. An example is that of a grainy looking sky in an high ISO image. All the pixels are blue but with different luminosity.

Chroma noise on the other hand is when pixels show different coulours when they all should be of the same colour. One example is that of an underexposed image brightened up during pp. Quite often both types of noises are present simultaneously.


Is this accurate? if so, then would you correct for chominance noise first and then luminance (assuming that such a choice exists). Does it matter on a practical level?

many thanks

Yes, I correct more for chroma (aka color noise) because I think it is very ugly. Luminance does not bother me as much, since it is that grainy "film like" noise and the more you process luminance noise the less detail you get (at least with basic NR software or in Lightroom). LR3 actually has a feature to add "grain" to your image.