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updated: 6/6/03

So try this experiment at home:

1. Put the D1 or D100 in Rear Sync mode.
2. Use Shutter-priority exposure mode.
3. Select an exposure that has a shutter speed of 1 second or longer.
4. Set your on-camera flash to D-TTL flash mode.
5. Set your wireless off-camera flash to Automatic wireless mode.
6. Take a picture.

What you should see is that the wireless flash triggers with the pre-flash from the camera (the first set of flashes). At the end of the exposure both flashes probably trigger again (the remote wireless flash might not flash again if it hasn't refereshed).

If you have a flash meter, try metering all this and see what you find (you'll have to isolate the light from each flash so the meter only sees one at a time). I've found that you can manipulate the heads to sometimes get a proper exposure, but it's a safe bet that it's not the flash exposure the camera is calculating.

The problem is the pre-flash. The D-TTL pre-flash contains 18 discrete pulses arranged in a time pattern:

              ooo oooo oooo oooo ooo ...(camera calculates)... Flash!

The wireless flash tries to match what the camera is doing with the main flash. It starts firing with the first pulse and stops with the last. Then starts up again when the main flash occurs. This has a couple of consequences:

• The pre-flash reflections measured by the camera are "augmented" by the wireless flash. There's a tendency for the meter to get confused by the extra light during the pre-flash.
• The wireless flash may not recycle fast enough. The response to the pre-flash causes the wireless flash to fire once, then it's asked to fire again very shortly thereafter. Depending upon battery condition and the amount of time before the second response, the wireless flash may not have enough oomph to match what the main flash is doing.

So forget about using D-TTL for wireless without help (keep reading). The best wireless solution you can obtain with the D100 and D1 series and all-Nikon equipment would be to put the on-camera flash in Automatic flash mode and the remote in Automatic wireless. The best wireless solution you can obtain with the D100's internal flash is to put it in Manual flash mode (through the custom settings), and put the remote wireless flash in Manual wireless mode. This, of course, means that you have to do precise manual flash calculations, especially since the internal flash always fires at the same value when in Manual flash mode.

That said, there are two ways I know of to get passable "quasi D-TTL" wireless results (though it seems to vary a bit with flash units):

1. Use an SB-26 as your remote wireless flash. Make sure that it the switch on the front is set to the "D" (delay) position.
2. Set the on-camera flash to Standard TTL. Set the flash exposure compensation for this flash, as desired (it will be reflected in the remote flash, too!).

or

1. Get a Wein Hot Shoe Slave (model HS Digital), which acts as a remote wireless trigger that ignores pre-flashes.
2. Plug any D-TTL flash into the Nikon digital body, and set it to Standard D-TTL.
3. Plug the remote flash (it doesn't have to have it's own wireless ability) into the Wein slave and set it to Automatic flash mode.

In general, I've found that this second solution tends to work best if you use the Wein-based flash as your primary light (remember, it's in Automatic flash mode) and the on-camera flash as your fill light. That means that I often dial down the flash exposure compensation for the on-camera light (another reason I want to be in Standard D-TTL; in balanced fill flash modes I lose the ability to control the exact flash level)>