I’ve just bought a pair of RadioPopper Cube, so here is a quick review of these units. What you get is just the RP Cube on the right, the JrX Studio receivers are sold separately with the cord. What the RP Cube does is enable you to adjust flash output levels ( on 3 separate flash groups ) right from your JrX Transmitter without having to run back and forth to your light sources for tweaking.
Radiopopper Cube are meant to work with their JrX Studio receivers, so the JrX Basic Receivers will not work. I found this out when the Cubes arrived so I had to send in my JrX basic receivers to be upgraded to the Studio version, which is $40/unit so its not too bad.
You flash will be attached to the Cube via the hotshoe, and the bottom of the Cube can be mounted on a lightstand, there is a mini-jack cable that runs from the Cube to the JrX studio receiver.
Your flash will need to be in TTL mode for the RP Cube to work so please refer to your manual to set it to this mode. For Canon 580 EX II see here.
The turning ON sequence is: attach the whole rig, turn on your flash, then turn on the JrX Receiver, then turn on your transmitter. However this is NOT enough to get it to trigger the flash when you take a picture. I had to turn the transmitter knob back and forth a little to make them “communicate” with each other, after that its all ready to go. Here are the test results!
It works great! Camera setting was ISO 320, f11, shutter speed 1/100. 8 exposures were taken when I turned the transmitter knob counter-clockwise in 8 rough increments and there seem to be a gradual and smooth increase in power. The transmitter knob direction is intuitive, just think of opening a “can of light”, the more you loosen it the more power will come out.
I felt there was enough fine-tuning in the power level for it to be practical when shooting, you can adjust the power until it’s just right. The setup is not too hard to get it ready, although the knob turning in the beginning is too much of a hassle I think. It would be great if you can turn it on any which way and its ready to go instead of having to memorize the sequence to get it to work. Despite that fact the Cube makes it very convenient for you to adjust power on the fly instead of walking back and forth to your light stand to tweak the flash output.
See also the related article for a DIY adding an mono-jack to Vivitar 285HV.