The light you trigger with your PC sync cable will set the second light off via optical light sensor. If the flash doesn't have one, you can buy one to slide into the flashes hotshoe or can plug into the flashes PC port.
Are their any downsides to using the optical light sensor?
Lag?
Flashzebra.com sells splitters. Very good company..Lon takes great care of his customers.
I highly recommend upgrading to a 5D. I went from a 20D->5D nearly two years ago and haven't looked back. It's just perfect for me, and you can't beat the image quality. Also, check out my old blog: hawkeyedownunder.blogspot.com ...Every pic on there was with my 5D from my Tasmania trip.
Wow I really want a 5d those pictures look great! makes me want to get a job just to buy one
Great link, could you link me to splitter I fail at webbing because I couldnt find it.
I'm thinking about going from PC port to RCA jack that way I can can order 10 ft. cables for $2. Any tips on how to go about doing that?
I think I want to get
LINK Then cut it in half an hook a RCA jack to it and I'll do this to 2 cables that way I end up with 4 converters. This way I can use a RCA splitter for the 2 lights
I do plan on getting a cheap radio set, but I would rather have a hardwire set that will be my back-up system later. This way I don't need to worry about broken radios or dead batteries, etc.
Cost
Wired: under $10
Radio: around $30 - $40 + Batteries