580EXII as master

Janice · 6 Nov 2009

I have a 580 EXII and a 40d.

I can't use the 580 as a slave to set off by my onboard so am thinking of a lesser unit for the slave (ie, one of the ones that Flash in the Pan is doing).

If I used this as the slave off camera, and put the 580ex on the hotshoe to use as the master... am I able to turn the 580 OFF if I want so it just sends a signal to the slave and thats all?

jontucker · 6 Nov 2009

Errr, no, I don't think so. You can only do that with the Canon 480EX, 580EX etc.

If you're going to go the cheaper route and get a non Canon slave, you won't get ETTL anyway so you might just as well go the really cheap route and buy a set of RF602's off FITP so you can use your 580EXII off camera in manual mode.

Janice · 6 Nov 2009

jontucker said:
Errr, no, I don't think so. You can only do that with the Canon 480EX, 580EX etc..

It IS the canon 580ex that i was wondering about putting on the hotshoe and turning the flash off so it signals to the slave via its infrared or something. FITP's flashes have slave so they would be able to be set off by this wouldnt they?

onform · 6 Nov 2009

The 580ex will only act as master to either the 430,550 or 580 ex range methinks.. As mentioned you are far better getting a radio trigger and receiver set and using your 580 off camera, then if you so wish you can expand with any quantity or brand of flash you want providing you buy a receiver for each one!..

HoppyUK · 6 Nov 2009

Janice said:
It IS the canon 580ex that i was wondering about putting on the hotshoe and turning the flash off so it signals to the slave via its infrared or something. FITP's flashes have slave so they would be able to be set off by this wouldnt they?

Jon is right. The way to do it is with an RF-602 transmitter on the camera and receiver on your remote 580 flash. That will work fine, but only in manual.

You can disable the 580's main flash, but the way it sends slave commands to other E-TTL enabled units is with the pre-flash (people talk about IR, but it's actually normal visible light) which goes off fractionally before the main flash so fast you can't actually distinguish it.

The problem is that the slave flash would respond to the pre-flash and go off before the shutter opens. (Edit: there are ways around this with extra electronic jiggery pokery, but why bother.)

If you want to use more than one flash, you could easily add another of FITP's Yongnuos. They have a built in optical slave which would then trigger in sync when the 580 goes off (in manual mode, the 580's pre-flash is switched off).

Having said that, it might be easier to use another receiver to do that rather than rely on the built in slave. They are so cheap and don't have any range or line of sight triggering issues.

david1701 · 6 Nov 2009

Janice said:
It IS the canon 580ex that i was wondering about putting on the hotshoe and turning the flash off so it signals to the slave via its infrared or something. FITP's flashes have slave so they would be able to be set off by this wouldnt they?

they're optical slaves so only respond to visible light, not the ir coms but would get confused by the preflash.

I'd say get the radio slaves and use the 580 manual off camera as they're long ranged and reliable and the 580 is a very good flash

(manual flash isn't hard to learn just screw around till it looks right, practice makes this a lot quicker)

jontucker · 6 Nov 2009

Janice said:
It IS the canon 580ex that i was wondering about putting on the hotshoe and turning the flash off so it signals to the slave via its infrared or something. FITP's flashes have slave so they would be able to be set off by this wouldnt they?

Yes I meant with one of those Canon flash units I listed as a slave AS WELL as your 580EXII on the camera.

I think everyone has pretty much answered your question though so I'll leave it a that... unless you have any other queries?

david1701 · 6 Nov 2009

if ya wana buy a 430exII you can have remote ttl without the 580 firing but I'm used to manual flash and I like the reliability you get with radio and the constancy you get from manual control

HoppyUK · 6 Nov 2009

david1701 said:
they're optical slaves so only respond to visible light, not the ir coms but would get confused by the preflash.

I'd say get the radio slaves and use the 580 manual off camera as they're long ranged and reliable and the 580 is a very good flash

(manual flash isn't hard to learn just screw around till it looks right, practice makes this a lot quicker)

There is no IR invloved. All the master-to-slave communication is done with visible light transmitted as strobed morse code type signals in the pre-flash. It can strobe at up to 50,000 times per second.

That is enough time to fire an exposure calculating flash, measure it, then then send further commands to say when to fire the main flash, and at what power output. All in the fraction of a second between pressing the release and the shutter opening. It's friggin quick.

If you have a quiet half hour, here's the Full Monty http://photonotes.org/articles/eos-flash/

Janice · 6 Nov 2009

Thanks all of you! I have plenty to think about now.

david1701 · 6 Nov 2009

HoppyUK said:
There is no IR invloved. All the master-to-slave communication is done with visible light transmitted as strobed morse code type signals in the pre-flash. It can strobe at up to 50,000 times per second.

That is enough time to fire an exposure calculating flash, measure it, then then send further commands to say when to fire the main flash, and at what power output. All in the fraction of a second between pressing the release and the shutter opening. It's friggin quick.

If you have a quiet half hour, here's the Full Monty http://photonotes.org/articles/eos-flash/

aaaah I thought the comms were IR and the preflash was visible, which is why CLS is meant to be more reliable

HoppyUK · 6 Nov 2009

david1701 said:
aaaah I thought the comms were IR and the preflash was visible, which is why CLS is meant to be more reliable

I think all modern auto-TTL systems use only visible light by way of the coded pre-flash.

IR is a bit of a misnomer. Even when the pre-flash master signal is sent via the ST-E2 (or Nikon equivalent) it is just a dark red filter over the flash to prevent it contributing to the overall oxposure.