Folks, The D1 etc have trouble with OTF flash metering because they have no F to meter off. Apparently the SB-xxDX flashes operate differently when connected to a digital camera compared to when they're on a film camera. What is the difference to their operation? Apparently they still do the preflash(es?) that are metered off the front shutter but what happens after that? -P.J.
If I remember right, the difference between the DX and the non DX is mostly electronic (primarily a slight voltage difference). Otherwise the system really works the same. Somebody can correct me if I'm wrong.
The DX flash electronics alows the D1 slr bodies to do the TTL metering during monitor preflash, not during the actual exposure as happens with other Nikon bodies. The DX does not fix the problem of metering reflected light off the imaging chip as the other answers hypothesize...
I had presume the SB-xxDX flashes have an extra mode where the camera will tell the flash the amount of energy to release before the main discharge rather than sending a "cut-off" signal during discharge. Mr Moose (sorry, I can's write that without smiling) says some interesting thingsabout flashes but nothing concrete. Then again it may be a Nikon trade secret.
I was surprised that the preflashes are not useful beyond 20 feet or so. Does this imply that 3D Matrix-balanced fill-flash is not possible beyond this distance?