I use Pocket wizard Plus II's.
They are amazing and I highly recommend them to anybody who want to go wireless. Essentially you need at least 2 of them. The Plus II's and the multimax's can go both ways (trans, receive). You put on on the hotshoe of your camera and then one hooks into your flash. How it hooks into your flash differs from flash to flash. Here is a link to the various flash cables you can use to connect the PW to the flash http://www.pocketwizard.com/HTML/cables2.asp
. I don't recommend using canon flash units since they don't have a good way to connect them to the PW. I made a miniphone to hotshoe connection for a 430ex I was using. You don't need the fancy flash unit anyways since when you use a radio wireless trigger, you loose a lot of the auto features that the spendy units offer.
You can also use the PW to trigger your camera AND your flash units from a remote source. Example of how I used that feature. I dug my camera into the snow at the end of a rail with 1 flash unit to the right and behind where the skier was going to be (for backlight). I had another flash unit to the left set up to provide fill flash to illuminate the face and front area. I got out of the way and just hit the remote when the skier was in the perfect spot.
You can find knock offs on ebay, but they are not as consistant and the range of the signal isn't nearly as good.
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