How to reduce Noise in picture

Noise reduction through Image Stacking

We can reduce the noise in a image by using the Image Stacking. It is a method of blending together a large number of photos of the same subject. When you do this right, what the photos have in common is maximized and what is different is minimized. Since the noise pattern varies from photo to photo, the noise gets smoothed out, but you don't lose fine detail the way you can with noise reduction software.

The following photo is a stack of thirty-two consecutive exposures (of which the above photo was the first). Notice how much less noise there is, while the fine detail of the radio tower and the tree leaves is all preserved. Note that there is absolutely no other editing, noise reduction, or other post-processing.

These are the simple steps.
1) Take the photos. You want them to be as close to identical as possible, so a tripod is critical. More photos are better, especially in powers of 2 (i.e. 4, 8, 16, 32, etc).
2) Open all the images in your editing software. I use Photoshop Elements 5.
3) Select one image and paste it as a new layer into another image. If all your images are the same size and orientation, you won't need to fudge the alignment.
4) Change the new layer's opacity to 50%.
5) Flatten the image. You now have an image that has all the shared detail and 50% of the noise of each root image.
6) Close the image you copied from. You don't have to save the changes.
7) Continue to merge pairs of images until you have half as many images as you started with. Now merge pairs of these images, and so on until you have one, final image.
8) Save your final image.