wireless ETTL, 1 master, 1 slave, ratios?

[Headcase650]

OK Im sure this is a repeat but I couldnt find it in the search.

I have a 550ex on camera as Master with flash turned on. I have Sigma 500 dg super as slave unit 1/A. They work together Im getting properly exposed pic's with both firing and with the master flash turned off and only the sigma firing. This is a big plus as I was worried because others have been having problems with blown out pics mixing flash brands.

I have read both manuals at least 3 times and something is eluding me about ratios. I understand how to set ratios between different groups of slaves. What I cant seem to figure out is how to set the master to slave ratio. I would like the master to be fill flash and the slave to be main light into an umbrella. I have tried dialing down the flash output on the master but I think what I am doing is dialing down FEC because it effects both flashes.

I know I can set the sigma as an optical and use the master in manual mode but thats not what I want, my vivitar slave do that just fine. I want ETTL.

Can someone more experiance with this point me in the right direction. I alread broused through the flash sticky thread but didnt see anything specifically explaining what I am asking.

Thanks,
Adrian

[robertwgross]

Adrian, you might be missing only a single step.

How about listing all of the settings you have for each flash unit.

Master/slave, channel, ratio, etc.

---Bob Gross---

[PacAce]

If you are using the 550EX as the master, what you need to do is set the EF500 as a slave in Group 2. You then press the SET/SEL button on the 550EX until the RATIO blinks. Then use the +/- buttons to select A:B. When you press the SET/SEL button again, the 1:1 ratio indicator should blink. Use the - button to set it to 1:2, 1:4 or whatever raio you want to set the flashes to. If you want the master flash to be the fill, the ratio has to be set to 1:x where X is a number bigger than 1.

All this is detailed in page 63 of the 550EX manual.

[Headcase650]

I think I figured it out. I read on here (redid my search) that the master unit is always group A (I still cant find that piece of info in the manual). I had my slave as group 1/A and this was my problem. My slave needs to be group 2/B with master set ratio to A/B = 1/2. Sigma groups are 123 while canons are ABC.

I did some test shots using my 300D because it already had a lens on it. The results are a little inconsistant, The exposure varies slightly from shot to shot. Does the wireless system work better with ettl-II. Ill have to give it a try with my 20D.

Does anyone know if a light modifyer on the master unit would interfear with comunication between flashes. I am considering getting a lightsphere-II. Would using it on the master unit prevent it from talking to the slave on a stand pointing into an umbrella.

Adrian

[PacAce]

Welcome to the world of the Sigma inconsistant flash behavior (I've experienced the same thing myself). :mrgreen:

As for the light modifier, as long as the slave can see the flash from the master, you should be OK. The only thing is that it'll cut down the distance you can have the slave away from the master but that shouldn't be a problem unless you're in a big ball room or something like that.

[Headcase650]

Here is something that bothers me about canon instruction manual. I read it again and all the slave ratio examples in the manual are with master flash off. and I still cant find where it states that the on camera master is group A.

[PacAce]

Here is something that bothers me about canon instruction manual. I read it again and all the slave ratio examples in the manual are with master flash off. and I still cant find where it states that the on camera master is group A.
Top of page 57, second bullet item.

[Headcase650]

I stand corrected.

I still think they should mention it again in the ratios section of the manual. But hey what do I know.

Thanks, all is well now. Im going to do some test shots with the 20D and am hoping for more consistant results with the ETTL-II. For some reason I dont think its a sigma issue because the 550ex is telling the sigma what to fire at. Hell I dunno, If anythhing the sigma makes a great back up for an on camera flash. All my testing with the sigma on camera have been flawless, performs just as well as the 550.

[PacAce]

I stand corrected.

I still think they should mention it again in the ratios section of the manual. But hey what do I know.

Thanks, all is well now. Im going to do some test shots with the 20D and am hoping for more consistant results with the ETTL-II. For some reason I dont think its a sigma issue because the 550ex is telling the sigma what to fire at. Hell I dunno, If anythhing the sigma makes a great back up for an on camera flash. All my testing with the sigma on camera have been flawless, performs just as well as the 550.
Try using the Sigma as the Master. If yours behaves in any way like mine did as a master, you're in for more than a couple of surprises. But I hope yours is more behaved than mine was. :)

[Headcase650]

well I just did about 20 different shots with the 20d using the 550 on camera and the 500 super off. It actualy turned out better than it did with the rebel. The shots are much more consistant.

To anyone considering adding a sigma to there line up as a back up or a slave to there 550 or 580 Ill give it a 9 out of 10 for fuctionality. Build is a little cheaper than canon's but so far Im actualy quite impressed.

The one thing I do like about it over the 550 I have is that the sigma can be used a an optical slave and I think thats great because I already have 2 vivitar 283 slaves. With the 550 on camera in manual mode I could have a very portable 4 flash set up or I could pc sync one of the vivitars and have a 3 flash setup.