Noses, That F. wrote: > With a software running on the source device and a light sensor attached to > that device, you know when the source device sent the picture and you see > when it appeared on the screen. > At least in theory, if the sensor if fast and accurate enought. Is it...? Right, but a serious approach would be to use a light to voltage/current sensor connected to something like a CRO. The sensors in an i1d3 are far from ideal for this (they are L2F), and it has unknown firmware and USB delays. Graeme Gill.