A quick question for you all :smile:. The IR bracket that Nikon sells to block the pop up flash light while using remote flashes seems to be out of stock all the places I have looked. What do you all use if not that one?
A 35mm film roll container can be used. Cut a window out of it that contains some unexposed developed film (completely dark) and at a 90° angle a slit so you can shove it over the flash head.
It's not pretty but it's effective.
You can just turn the pop up flash off. It will still trigger the remote flashes. Set it to "- -" (D300 manual page 294)
I thought the pop-up flash communicated with OCF's via different pulsed flashes... Wouldn't covering it up prevent it from doing this. You can just set it to master mode and change the output to nil like YoMoe ^ said.