After the posts on pre flash and flash triggers I have given some thought to the subject.
I see Duncan has got there before me with a couple of experiments so I will throw mine into the pot.
I had a read of my instruction book to ensure that pre flash would be triggered and set the D100 and the D2X up for an experiment. The basis of this experiment was after a flash test, as I was unable to notice the pre flash then its output power is a lot less than the main flash. If this was true then would a black flag as per the attached graphic work. The black flag should in theory shield the remote sensor from the low powered light yet allow triggering by the main flash.
I was unable to prove this, and attach two pics from the test. My slave is so insensitive that no matter what I did I was unable to get it to trigger through pre flash. This does show at least that 1) pre flash is indeed low powered, and 2) there is a sensitivity difference between remote triggers, in that some are blind to the pre flash.
Two pics attatched.
Camera settings on both cameras was Program Mode, 3D Matrix metering and the SB80-DX was set to DTTL.
1) Slave flash OFF. The slave trigger is highlighted in this shot and the Metz 45 in the background is what it is connected to. On camera flash distance to the trigger was 30 inches. So plenty near enough to get preflash trigger when the Metz was turned on. Positioning of the Mez was such that we could see in the image if it fired on time, or was triggered by the pre flash, in which case it would register as OFF. ie fired before the shutter opened.
2) Slave Flash ON . The underexposure here is because the Metz is a far higher powered unit than the SB80-DX that was on the camera. The camera has given correct exposure for the Metz flash reflector. You can see the light from it in the models chimney.
The conclusion from this is, that we need someone with a different remote trigger to try a black flag experiment. Black flag would be a bit of card or such taped to the unit to shied the remote sensor from direct line of sight from camera flash.
Don