A question for all digital camera and image buffs out there:

I learned about Digital Noise Filters recently (elsewhere on this site, I believe), and someone strongly recommended applying such a filter when processing images taken with digital cameras.

I tried it (using Paint Shop Pro XI) using the default raster size and a quarter of the default. In both cases, the image has not gained but actually lost detail. Mind you, I used high-res images (a 6MB camera) of grainy surfaces (sandstone).

Is digital noise an effect inherent to the CCD, and what factors determine its proportion? What's the deal?