We work on high accuracy detection efficiency at photon counting levels. This is a particularly difficult task as photon-counting detectors can only handle very low levels of light before saturating or being destroyed, (that is 10-10 W) while typical detector calibrations require significant amounts of light (10-4 W) so that the noise of the detector does not lead to inaccurate measurements. To bridging this gap we have created some very high gain but very low noise detectors to be used as transfer standard devices to allow the efficiency of photon-counting detectors to be accurately determined. If you have an interest in such accuracy we would be very interested in a potential collaborations.