because I don't want any on camera flash because that flattens images and getting light from the pop up flash not to hit the subject but still reach the optical slaves would be a pain.
Radio would be nicer but the effect of the on-camer flash on the subject can be controlled to nearly zero.
I use a small on-camera strobe (a Nikon SB16) turned backwards to hit the back wall or up at the ceiling. Typically I can use 1/16th power. so my on-camera trigger flash is maybe 4 or 5 stops below the other lights so it has no noticeable effect.
Now that I have a power pack system I connect the optical slave to the power pack with a long PC sync cord and I'll mount the slave on the back wall and aim the SB18 directly at the slave. With this setup I can run the on-camera strobe at the lowest setting. The best part is the re-cycle time is near zero.
Radio would be nicer. With my medium format camera I used a wire. The Mamiya RB67 lacked a hot shoe and only had a round sync terminal. There is really nothing wrong with a 25 foot cord
I have an underwater system too. On that system my external strobe has an optical slave but I block the on camera slave with a metal plate and run an optical fiber cable from in back of the plate to the slave sansor You are right, I absolutely did not want the on-camera light to hit the subject.
