Adding noise. The amount of noise.

[dognose]

I'd be interested in knowing how to do this as well. How to add just a little noise.

[magick]

The noise attenuation is fixed as constants in the magick/effects.c module in method GenerateNoise(). You can always add more noise by calling the noise command line argument more than once but you can't reduce the noise without modifying the source code at this time.

[anthony]

You could overlay a random amount of a random image...
See DIY random noise
http://www.imagemagick.org/Usage/canvas/#random
Of course -FX is slow, but +noise poisson isn't.

I may have to re-write that part of IM examples to use it

However you are right -noise and +noise could probably do with a rewrite.
Volunteers?

[anthony]

A special +noise Random method was created that will replace the current image with a purely and linearly random noise. This removes the need for using the very slow -fx to generate pure random noise images. From that start you can then modify the image to generate any noise pattern you like.