Glossary of Light Microscopy Terms

Binning

Binning is a process used to increase the sensitivity of a CCD camera by combining the charge from adjacent pixels to boost the signal-to-noise ratio in the image. If we imagine a hypothetical camera (see below) with a chip consisting of 4x4 pixels and we apply a binning factor of 2x then 2x2 arrays of adjacent pixels will be combined together to form an array of 'super pixels' that are four times the area of the originals and contain the combined charges of the adjacent pixels. This improves the signal-to-noise ratio because CCD camera readout noise often obscures low signals. If the readout noise of the hypothetical camera below is 25 grey levels then most of the signals in the image on the left will be indistinguishable from noise. By combining the charges from adjacent pixels the readout noise threshold is easily exceeded in most of the pixels in the image on the right.

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