An image quality measuring method enables a biometric image to be evaluated to determine whether the biometric image data are adequate for identification processing. The method includes converting a biometric image to dimensionless image data, filtering the dimensionless image data with a band pass filter, identifying a plurality of portions in the filtered data as containing identification features, each portion in the plurality having an information measurement that indicates feature content greater than portions in the filtered data that are excluded from the plurality, and measuring clarity for the biometric image from the identified plurality of portions in the filtered data.