Shedding some light on the sources of image noise ...

RICHARD BUTLER, DPREVIEW:

"How would you react if I told you that the aperture and shutter speed you choose make more difference to image noise than the ISO setting? You might be surprised to discover that a lot of the noise in your images doesn't come from your camera at all: it comes from the light you're capturing.

"To really understand what's going on in your camera and, hence, how to get the best results out of it, it helps to understand a little bit about where noise comes from. Noise is widely misunderstood and yet it lies at the heart of most technical assessments of image quality and camera capability.

"In simple terms, noise is any variation from the true 'signal' that you're trying to capture. Visually it's immediately recognizable as pixels of unexpected brightness or color, most easily seen in areas where you might otherwise expect a smooth result. The first thing to realize is that there are several mechanisms that contribute towards noise and that all of them can play a different role, even within a single image.

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