Experimental and theoretical comparison of photon-counting and current measurements of light intensity.

The effect of gain variation on the integrated output-charge distribution of a photomultiplier tube is investigated experimentally and shown to be a predictable function of the multiplier single-electron response. Standardized or nonstandardized pulses recorded using either capacitive or digital storage are considered. Theoretical values for the moment-generating functions and variances (noise powers) of the charge distributions obtained in these four cases are given, and the role of these various distributions in determining the length of time required to achieve a given accuracy in a light-flux measurement is discussed. The experimental measurements adequately confirm the theoretical predictions. The work includes a critical discussion of the field of theoretical and experimental noise investigations in photomultiplier tubes with regard to their relevance in the present state of technology.