How to remove or reduce noise by selecting tonal ranges. This is primarily for microscope images, although it is useful for images from other sources. Not available on earlier versions of Photoshop: the Image Size method is recommended.
How to Reduce Surface Noise in GIMP
A similar tool is called Selective Gaussian Blur:
Filter > Blur > Selective Gaussian Blur
In dialog box, change Delta amount and Radius to get a small degree of blur but to remove overall graininess. Check split screen to better view result and use + symbol to save Preset
How to Reduce Graininess in Image J
- Under Plugins, select A Trous filter.*
Start by using default settings, then change coefficients iteratively.
- Filter will likely work best if hot pixels are removed first.
*To load plugin: Load the A Trous plug-in (A Trous.class) to Image J: Locate plugin folder in the Image J program and drop in.