Going to try and do a shoot underwater. I'll be about 3 feet deep max shooting down, at a angle, onto a model about 4-8 feet deep. I have 4 Einsteins. I plan on using a cybersync to fire them. Camera is in a case that has room for the cybersync. I know light fall off will go quick. Any other input from anyone?

Thanks

Also, if range is a concern as others think, line of sight is best for radio signals. With you maybe even below the Einsteins, consider hanging them upside down if that is a more unobstructed path.

The problem is not so much of range, but attenuation. Water will attenuate radio signals rather effectively. Line of sight issues as far as what side of the light the reciever is on pales in comparison. 6-12" is about as much as you can hope for, and is certainly not guaranteed.

A hypothertical solution: If your camera can set the pop up to manual, do that and set it as low as possible. You can then attach an optical slave to the CST and place it in a clear water tight case (WalMart, <$10 in the fishing and camping section). You can float the case over the camera. If you tether the case to your camera housing with a string, it will not float off.

Do you have any other speedlites? If so, put one on "M" on the camera. Put the SB900 (SB800 and some other Nikons will also work) in SU4 mode and connect the CST to the SB. The SB will act as the optical trigger.

If you can do the shoot without submerging the CST, then the case will not be an issue.

Ok thanks. Let me make sure I understand. I have 6 SB-900s. So put a SB-900 on the D3S on manual inside the case (I can do that). Put a second SB-900 in SU4 and connected to the CST above water either in a clear case or on the side of the pool. This will trigger the optical on the Einsteins.