Regular readers will be familiar with the noise levels graph that we publish in selected camera tests, but you may have wondered how we arrive at the figures shown in the graph. To produce the data that we plot, a stepped 'wedge' is photographed by the camera on test at every available ISO sensitivity setting, and these images are examined in a scientific analysis program. The wedge (see example on the lower right) is a grainless target, lit by uniform lighting from behind. Theoretically, in the final image the pixels should be the same tone in each segment. If some pixels have a different tone from the rest, they represent noise. To measure the amount of noise, the analysis program counts the number of pixels that are not of the expected tone and produces a figure as a percentage of the total, shown on the y axis of this graph.
Turn to pages 71-73 for AP explains... in-camera noise reduction, where you'll find an explanation of how digital cameras are designed to minimise noise, and how you can use your camera's settings to reduce noise in your images
This is an example of a stepped wedge. The wedge that AP uses is a transmissive sheet, with several segments that go from being totally opaque to completely transparent
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Compared to film cameras, digital cameras are easy to use, fun and extremely versatile. Every day there’s more features being designed. Whether you have the cheapest model or a high end model, digital cameras can do an endless number of things. Let’s look at how to get the most out of your digital camera.