Noise is random.

来源: 于 2007-02-22 11:06:46 [博客] [旧帖] [给我悄悄话] 本文已被阅读：次

For example, at a certain pixel, assume its signal is 100 and noise is 10 in one photo (so total value on that pixel is 110). On a second photo, the signal is still going to be 100, but noise could be -5, so that the total value for that pixel is 95.

When you add the two photos, you get the pixel value of 205 (signal 200, noise 5).