Help with Wireless ETTL Requested

[scottbergerphoto]

I am using two 550EX's, a light stand and an umbrella as a portable lighting kit for my 10D and 1D Mark II. I use wireless ETTL. When I use ratios, all works as it should. I am now trying to use FEC on each flash instead of ratios as described in Vincent Laforet's article in www.sportshooter.com. (http://www.sportshooter.com.) It seems no matter what I do, regardless of what FEC I put on the Slave flash, it gets overridden by the FEC on the Master. As a test after much frustration, I pointed the Slave at the subject and the Master at the Slave so as not to fall on the subject . I set the Slave to +3FEC and the Master to -3FEC. The picture was grossly underexposed. I then set the FEC on the Master to 0. The picture was normally exposed(remember the Master is not pointing at the subject) Clearly the Master is overriding the settings on the Slave. I have the Mark II in Manual Mode so there is no automatic fill flash reduction and it is turned off in Cfn.s on the 10D.
Can someone tell me what I am doing wrong?
Regards,
Scott

[scottbergerphoto]

Bob Gross where are you when I need you? :shock:
Scott

[Jon]

Couldn't find the article you referenced at www.sportsshooter.com (http://www.sportsshooter.com). The other is a target-shooting site, which certainly won't help! Could you maybe point us to it a little more clearly so we can see what you're trying to make work?

[scottbergerphoto]

The 550EX's in ETTL Mode with one set as Master and one as Slave are supposed to allow for FEC to be set individually on each flash. For some reason I am finding that the FEC set on the Master is overriding the FEC on the Slave. That is not supposed to be the case.
Here is the link:
http://www.sportsshooter.com/news/450
Regards,
Scott

[robertwgross]

Bob Gross where are you when I need you?


(1) I don't own two 550EX units.
(2) I don't own either of those cameras.

So, there isn't much to say.

---Bob Gross---

[Jon]

I'll have to re-read that carefully with a 550 and manual in front of me . . .

Just a thought - could having the Mk II in Manual Mode have anything to do with it?

[Quinn Porter]

I don't have a manual with me, but could the problem be with your group settings? Perhaps the two flash units are in the same group, but they need to be in different groups as they would be for ratio use.

Just a thought.

[Mark Kemp]

There is always the low tech solution, set all the flashes to full power and move them backwards and forwards to change the strength.

Hopefully someone can help you out with the flash settings but in the meantime it might help out.

[scottbergerphoto]

I don't have a manual with me, but could the problem be with your group settings? Perhaps the two flash units are in the same group, but they need to be in different groups as they would be for ratio use.

Just a thought.
Master is A by default, slave is set to B. I know the Manual by heart!
Thanks anyway,
Scott

[slin100]

The manual does certainly imply that it should be possible to set FEC on a slave (pg 70), so I don't know why the Master is overriding the slave. :?: Try turning flash ratios on or off. One of the settings may allow FEC to be uncoupled.

Another possibility is to put the slave in group C. The manual explains that setting the (A:B):C ratio is actually done in terms of FEC. The adjustment is done on the Master by adjusting the group C FEC, not the main FEC.

If you are trying to obtain a FEC difference between two groups greater than 3 stops (i.e. ratio greater than 8:1), I have a feeling that that's not possible, so you may as well stick to using ratios.