Noise vs grain

[spidermike]

I have seen many photos taken on film where the grain of a film added to the atmosphere of the shot or enhances the message (typical ones being of grimy backstreets or inside working steel foundries).
When explaining noise to newbies (of which I count myself as one), it is often described as analogous to grain yet the intention in post processing seems to be to remove noise wherever possible.

Has anyone used noise in a similar way to grain? Or is the 'character' of noise so different to that of grain that it doesn't work?

[stamper]

I have seen many photos taken on film where the grain of a film added to the atmosphere of the shot or enhances the message (typical ones being of grimy backstreets or inside working steel foundries).
When explaining noise to newbies (of which I count myself as one), it is often described as analogous to grain yet the intention in post processing seems to be to remove noise wherever possible.

Has anyone used noise in a similar way to grain? Or is the 'character' of noise so different to that of grain that it doesn't work?
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It certainly can be added to a B&W image. There are two types of noise in Photoshop. It is a matter of taste which you use. There are variations as to how you do it. The noise can be done via a layer and opacity varied and the noise can even be sharpened. The noise can be masked into certain areas. Some people add noise to a colour image to take away the "plasticky" look. Do a google search and they will be a lot of information for you to expiriment with.

[Dale_Cotton]

I'm aware of two main differences between noise and grain.

First: noise happens to individual pixels, while grain crosses pixel boundaries. In colour film "grains" are actually dye clouds which are much larger than the individual silver grains seen in b&w. But even for b&w film the grain does not line up such that a single pixel is either a single element of granularity or a single element on subject matter. In practical terms digital noise is more a pinpoint effect while granularity is more spread out.

Second: noise in Bayer pattern systems has a colour component as well as a luminance component. Noise Reduction software can be set to remove colour noise, while leaving luminance noise. This not only comes closer to resembling film grain; but also chroma NR involves much less detail smearing than luminance NR.

The upshot of all this is that digital noise tends to look very different from film grain.  To my eyes at least that look is less an organic part of the image and more an arbitrary intrusion to the image. More like measles and less like freckles. ;) But that's an aesthetic judgment and it may be that a generation that grows up with digital noise instead of film grain may have just the opposite response.