The shutter ratio of a proximity focused ITT F4128 microchannel-plate (MCP) photomultiplier is investigated for gated photocathode-to-MCP gap voltages. At counter potentials of greater than 3 V, the shutter ratio is better than 1013 for incident light with a wavelength longer than 600 nm.

The noise factor of the HAMAMATSU R 928 circular cage photomultiplier has been measured. It is demonstrated that the optimum mode of operation with respect to the noise is the one with constant interstage voltage distribution. Different effects contributing to the overall noise factor have been identified.