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The signal-to-noise ratio (SNR) is used in imaging as a physical measure of the sensitivity of a (digital or film) imaging system. Industry standards measure SNR in decibels (dB) of power and therefore apply the 10 log rule to the "pure" SNR ''ratio'' (a ratio of 1:1 yields 0 decibels, for instance). In turn, yielding the "sensitivity." Industry standards measure and define sensitivity in terms of the ISO film speed equivalent; SNR:32.04 dB = excellent image quality and SNR:20 dB = acceptable image quality.〔ISO 12232: 1997 Photography – Electronic Still Picture Cameras – Determining ISO Speed here〕 ==Definition of SNR== Traditionally, SNR has been defined as the ratio of the average signal value to the standard deviation of the background: : However, when presented with a high-contrast scene, many imaging systems clamp the background to uniform black, forcing to zero, artificially making the SNR infinite.〔 〕 In this case a better definition of SNR is the ratio of the average signal value to the standard deviation of the ''signal'' : : which gives a meaningful result in the presence of clamping. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Signal-to-noise ratio (imaging)」の詳細全文を読む スポンサード リンク
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