Posted 09 January 2010 - 02:24 PM
Grain has to do with the size of the silver crystals in film and how they clump within the emulsion layer, whereas noise is an electronic phenomenon whereby the desired signal is destroyed by electronic noise. Grain tends to be more uniform across an image (at least into the midtones) as is evident in the first image of Tim's whereas noise tends to manifest more in the shadows and in underexposed parts of an image. Film will exhibit characteristic grain pattern for that film irrespective of under or over exposure. Grain patterns vary according to the emulsion and developing process, which is why in the film days photographers may have preferred the look of one film over another. As far as I am aware noise patterns do not vary in appearance, say from sensor to sensor, except in the degree of noise, and pixel size.
Sure grain was not always desirable, but at times it was actually desired to impart a certain textured look to the image, noise is rarely desired in the same way. That is why filters still exist that impart the look of one film or another to digital images. Underwater photography probably has fewer situations where the textured look of grain is desirable, except possibly wreck photography. Topside I would frequently choose to impart a grainy appearance to images in both landscape and portraiture situations.
There are certainly similarities in that both may detract from the image, and both impart a granular appearance, but the textures they impart certainly look different to me.
Edited by loftus, 09 January 2010 - 02:32 PM.
Nikon D800, Nikon D7000, Nauticam, Inons, Subtronic Novas. Lens collection - 10-17, 15, 16, 16-35, 14-24, 24-70, 85, 18-200, 28-300, 70-200, 60 and 105, TC's. Macs with Aperture and Photoshop.