will the Canon Speedlite 580EX II work off camera with the 5D Mark III?

[Skirball]

Without additional hardware?  No.  There's no internal flash for optical triggering, and no manufacturer is currently making radio triggers built into the camera body.

I recommend the Yongnuo RF-622 for triggering off camera.  If you don't need eTTL then save some money and get the RF-602.

[diverhank]

I concur with Skirball.  My solution is an optical one, I got a Canon ST-E2 to control the 580EXII remotely

[WahoGT]

For flash off camera, I usually prefer one of the long 33ft ETTL cords from Syl Arena's OCFgear.com . Your camera doesn't know the flash isn't on the hotshoe, so it gives you full functionality (ETTL, HSS, second curtain sync, can still act as a master, etc) and its probably one of your cheaper options as well, since you don't need anything extra on camera to act as a master flash (your corded master can be your key/fill/kicker/whatever). It also lets you use the LCD of the camera to change settings, so you don't have to keep walking over to your flash to change settings while shooting, like with manual triggers.

[TCampbell]

A 580EX II can work off-camera but the camera has no "built in" way to tell the flash to fire.  There are several options.

The Canon brand option is to use any other speedlight or speedlight controller capable of communicating via IR (the 580EX II's only "internal" way to communicate remotely is via IR).  The downside of IR is that it requires line-of-sight (IR will bounce off walls and ceilings in enclosed situations but that obviously isn't going to work in large open spaces or outdoors.)

You can buy a Canon ST-E2 which is the IR based commander.  You could also buy a 2nd 580EX II or the new 600EX-RT (the 600EX-RT can link either by RF or IR -- with a 580EX II you'd like it via IR).  

You can use 3rd party radio triggers such as the PocketWizard MiniTT & FlexTT (note these come in Nikon-specifc and Canon-specific versions so you'd want to be careful to get the correct versions.)  The 580 has been a bit troublesome for the Pocketwizard FlexTT because some 580's put out enough RF interference to reduce reliability (there are several "shielding" options to fix this as well as a service which internal fixes the 580 so this is no longer a problem.  A stock 580EX II can have a problem.)

If you don't use TTL modes then there's no problem -- a PocketWizard Plus II or Plus III should work reliably.

You can also use a sync cord.  The 5D III and 580EX II both have standard sync terminal sockets on them (on your 580EX II it's covered by a round rubber flap on the lower left side just above the foot.  On your 5D III it's under the rubber flap on the left side of the body marked by the lightning bolt symbol.)

If you were going to invest in a remote triggering option, I might just go for buying a 600EX-RT and using it as a commander.  This gives you (a) a 2nd flash and (b) starts building up a system where you can use Canon's radio system while (c) also allows you to remotely control the 580EX II.

While at a nearby camera store last week, I noticed they had a small pile of PocketWizard Plus II's in their "used" gear display cabinet. I asked about them and their answer was "Yeah... a lot of guys having been trading these in ever since Canon came out with the 600EX-RT."  (I own a pair of 600EX-RT's and completely understand why... it's a very nice system.)

[dr_d]

So, there's a great cheaper solution to this problem that you can access without buying any more speed lights (if that is your wish).  Use a lower cost [MOD NOTE: Link removed per FORUM GUIDELINES]

[RobertTheFat]

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@dr_d wrote:

So, there's a great cheaper solution to this problem that you can access without buying any more speed lights (if that is your wish).  Use a lower cost [MOD NOTE: Link removed per FORUM GUIDELINES]

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It's not altogether clear who you're talking to here, with or without the censored reference. This thread was last updated four years ago, and a lot ot equipment has come and gone in the intervening time period.