The Standard Reference Method or SRM is one of several systems modern brewers use to specify beer color. Determination of the SRM value involves measuring the attenuation of light of a particular wavelength (430 nm) in passing through 1 cm of the beer, expressing the attenuation as an absorption and scaling the absorption by a constant (12.7 for SRM; 25 for EBC). Auxiliary "deviation coefficients" (see Augmented SRM below) can pick up the remainder and are necessary for fruit beers and when subtle color differences in malt beers are to be characterized.