Tamas970
Sorry for the delay in replying - been away for a few days.
The example of Hedwig's unit that I have seen was nice - much more sophisticated than the MOSFET version. I did make it work by firing the LED directly into the fibre optic bulkhead connector, but did not fit it to the camera as it mounts on the hot shoe....and mine is already used by the camera pressure lead detector.
The MOSFET circuit I am using has 2 x 12V LR23 batteries in parallel, with the 4 high power LEDs mounted in series. Hedwig uses 2 CR button cells of 3V each, and his LEDs appear to be in parallel.
Herewith pictures of my version. One shows the batteries and circuitry mounted under the camera tray, the other shows the hot shoe connector with the wiring break for the flash, and you can see the 4 LEDs mounted on a board directly under the bulkhead connector. Units are connected with computer plugs. Wiring is rather untidy - I will make another one when I have a minute and tidy things up.
Pete
Ah, the photos failed. I will try again.