Sale on canvas prints!
With film cameras this was known as ‘grain’. I went through a phase of using high speed b+w film and did certain things during the darkroom print developing process to get grain - the more the merrier as it was fashionable at the time. Now noise has become the bugbear of many photographers. There are various ways to avoid it during processing/editing, but it is best to try and minimize it initially in the camera because it's impossible to completely eradicate once present. Observing the following simple procedures should assist in eliminating most visible noise.
1. Shoot in RAW mode and convert to 16 bit tiff files for all editing.
2. Make sure there is plenty of light to illuminate the subject or scene.
3. Long exposures in dim light can generate noise but more recent dslr cameras allow for high ISO values so noise in dimly lit situations is not such a problem.
4. Use the lowest ISO setting possible - overriding your camera’s auto ISO setting can often be a good idea but a tripod may be required in those situations.
5. Where there is a lot of contrast of light and shaded areas in a subject, try different exposure value settings (EV) to establish which one gives good rendition of both light and shaded areas - an alternative is the use of high quality ND filters or graduated filters to cut down the contrast
using a tripod and taking several different exposures of the same subject, then layer blending them in Photoshop can also yield good results by choosing the best exposed parts of each image.
6. After transferring your shots to the computer and converting the RAW data, do as little processing as possible that generates noise. Changing colours of things and monotone conversions can whip up a storm noise-wise, so care should be taken to prevent this alteration of pixels if a smooth outcome is desired. Usually, the more that is done of a general nature to an image during processing, the worse the degradation can get, so experimentation and practice is required to find out what suits you and the situation best - and that can differ from image to image. HDR work can produce lots of noise also, but that's another story.