Noise makes photos look kind of dull and introduces all sorts of artifacts in the images you capture. You most often see digital noise in photos shot in low light. Long exposures are also prone to it.
Unfortunately, unless you have full control over your camera’s settings, there is little you can do about noise. Even if you are in full control, you cannot completely avoid noise, especially in less than optimal lighting situations.
Now for the good news: To a certain extent, noise can be removed in post processing. This short guide will show you how.
Step 1. Working with Channels.
Open your image. You will be reducing noise in each color channel separately, so enable the Channels palette (Window>Channels).
Step 2. Applying Surface Blur.
In the Channels palette, select the Red channel, which is the first under RGB from the top. With the channel selected, go to Filter>Blur>Surface Blur. When the Surface Blur panel appears, set the radius and threshold of the filter until noise is hardly visible, detail is retained, and contours are still sharp. Radius controls the amount of blur, while Threshold controls the difference in tonal values for the blur to be applied.
TIP: Only select one channel at a time. The channel is selected correctly if the photo turns into black and white.
Step 3. Repeating the process.
Repeat the process described above for all the remaining channels, adjusting the surface blur settings to the amount of noise in the specific channel you are working with. Don’t overdo the blurring or you risk damaging the quality of your photo.
Step 4. Sharpening the image.
If you notice the image has become too soft after running the blur filter on the various color channels, you can apply a bit of sharpening to the image. Go to Filter>Sharpen and choose Smart Sharpen.
In the filter’s panel, set the desired amount of sharpening you’d like and radius values. Start with low values and increase them while using the preview. Check the “More Accurate” option for the best results.
Step 5. More filters to remove noise.
There are all sorts of alternative methods and tools to help you remove noise from your photos. A few commercial filters you can try are: Noise Ninja, Topaz DeNoise, and Neat Image.
It's just noise.
Don’t think of noise as you shoot or let it intimidate you. Even if total removal is impossible, noise can be reduced to acceptable levels. And remember that nothing compares to a clean photo: Try to create optimal lighting situations around you as often as you can, and keep your ISO as low as your camera allows.
Edited in Adobe Photoshop CS5.