Originally Posted by ivzhao
i tired to use my newly purchersed R2a to shoot some studio shots, but it didnt work. i tried plugin the cable into the Synchro Contact(the one on the side), and i also tried plug in the cable into the hot shoe(is it what it called? the one on the top) with a convertor, but neither worked?
Don't worry, there's nothing wrong with your camera or studio flash unit!
The reason your studio flash didn't work is that the flash sync circuit on an R2a (or R3a) is polarized.
That means the flash's trigger current will flow through it in one direction, but not the other.
Old cameras didn't have this problem because their sync circuits used a mechanical switch. Many modern electronic cameras use a transistor instead -- faster-responding and more reliable, but it does introduce this polarity problem.
Easy fix: If your studio flash unit uses a sync cord that plugs into the power pack via an "H" prong connector (common on American-made flash gear; looks like a regular household plug) then just turn the connector over and plug it back in. This will reverse the polarity of the sync circuit.
Harder fix: If your studio flash unit uses a sync cord with a coaxial plug (common on European flash gear) then you'll either have to order a "sync reverser" from the flash manufacturer, or snip the cable and switch the two wires inside to reverse the polarity.
Alternate solution: Buy a "sync isolator" such as the Wein Safe-Sync. This uses its own switching circuit to isolate the camera's sync contacts from the flash circuit, and should enable your flash to work without regard for polarity.
Another alternate solution: Put a very weak hot-shoe flash in the camera's hot shoe and use a slave-eye unit on the studio flash to fire it.
People don't normally have this problem with hot-shoe flashes because the polarity of these is fairly standardized. With studio flash gear, though, there's no dominant standard, and there's no dominant standard for cameras, either. When I ran into this problem myself (with my R3a and Epson R-D 1) I found that both the Voigtlander and Epson require one polarity, and my Nikon D-100 requires the opposite polarity. So, I've had to mark my power packs with which way the H plug needs to face for each camera, and have wired up two different sync cables for the portable unit I use that has a coaxial sync connector.