This is a photo I took, in the cellar of a winery, with no flash. Some other ones (like this one, and this one, both taken in slightly brighter light) came out with the effect I was seeing - but the cellar was just too dimly lit , so I ended up with a lot of noise. Did I expect a great photo? No. What I expected, and got, was a good learning experience - an idea of how much under-exposure I can compensate for in the post-processing phase.

Eliminate Noise From Your Photos

The ability to change your Digital Camera's ISO level is a mixed blessing. Increasing the ISO allows you to capture sharp pictures in low light by increasing the camera's sensitivity, but it also adds unwanted digital noise to your picture--which looks like the grain you'd see in a print made from very fast 35mm film.

[Via Digital Photography Blog: Eliminating Noise From Digital Photos]