The following is a brief tutorial on removing image noise using Photoshop. Removing noise is a process of trial and error while making sure as much image detail is retained as possible.
1. From the Filter menu select Noise, then Reduce Noise.
2. This will open a dialog with an image preview and a number of sliders.
3. Set the Sharpen Details slider to 0, this will prevent the filter from applying sharpening. Any sharpening should be done afterwards using Photoshop’s dedicated sharpening filters (Unsharp Mask or Smart Sharpen).
4. Zoom in and check for random red, blue or green pixels. If any exist the image contains Colour Noise.
5. To clean colour noise set the Reduce Colour Noise slider to 0% and slowly increase the value until the noise is removed. You may find its not possible to remove all noise without removing detail from the image. In which case find a happy medium between the two.
6. The second type of noise is called Luminance. These are pixels of different brightness levels (Black, white and gray) to the surround pixels.
7. To remove Luminance noise first reduce the Strength slider to 0% and slowly increase the value until the noise is removed. Then use the Preserve Details slider to restore as much detail as possible without bringing back the noise