600EX RT overexposing in ETTL

[rcarvillephoto]

I am using a 5dMKiii with a 600 EX RT and a wizard connected via the sync port on the camera body.   (Wizard fires the room strobes I set up to as fill light for the entire room. 

While shooting events I the 600 is overexposing majorly and randomly.  I have had to knock the EV on the flash all the way down to -3 and occasionally it even overexposes on that setting.  I can't use manual mode on the flash as I am in a variety or distances and lighting situations.  

HELP!  I have searched the internet high and low and the only thing I foudn was that on ETTL the flash only meters via the center weight point.  So for example I focus on the eyes then recompose.  When I recompose the center weight moves to a black jacket.  So instead of exposing for the face it goes for the black jacket.  This makes sense to me.  My question is how do I change that to say lock the meter when focusing?

Thanks in advance!

Ryan

[Skirball]

It's a fairly complex issue to diagnose at once, and I don't use PW so I'm not sure I can help there.

First is the over-exposing.  Are you sure it's from focus-recompose, or is it possible that something isn't working properly?  I'd check to make sure everything works properly with the flash on-camera first.  Having to move down -3 eV is a lot.  Too much.

What camera mode are you using?  Using an auto camera mode is going to introduce even more variables, can you use manual?

I didn't realize that eTTL only works on centerweighted.  Truthfully I don't use eTTL near as much as manual.  But usually I keep FEC down a stop anyway when in ETTL.  I'd rather lean towards underexposed than over.

This probably isn't what you want to hear, but...  you own a 5d3 and you're focus and recomposing?  Put those other 60 AF points to use!

[rcarvillephoto]

Hey Skirball!

Thanks for your reply.

OK so first the wizard has nothing to do with the communication from the flash and body.  I just wrote it so you could understnad the set up.  

Second, I shoot only in manual on the camera.  Generally with events it is f/4 125 @ 1000ISO.  My first thought was that the flash unit was messed up.  3 or more stops is crazy!  But after speaking with a fellow Canon user using the same setup, he has the same issue.  

I wish I coudl use manual on the flash, but it just doesn't work when photographing dancing and candid when distance becomes a variable.  

[Skirball]

Interesting.  Where is your flash, on your person somewhere or on a stand?  Do you have another eTTL flash, that isn't a 600exRT, that you could try?  I could see overexposing a bit, but 3 stops makes it pretty much unusable, and people use off-camera eTTL all the time.

As I said, I don't use eTTL much, and when I do it's usually on-camera.  But I have done it before, on stands in modifiers, using Yongnuo 622s.  The exposure varies a bit, but I've never been 3 stops off.  Are you using the flash for side lighting or rim light, or something that perhaps gives the metering some issue?

I've also never used the sync port, I've always gone through the hotshoe, but I'd think that wouldn't matter either.

[rcarvillephoto]

I am using it on the hot shoe. On camera flash. The other flashes (elimchrom or profoto strobes) are controlled via the pocket wizard. So the only communication is between the camera and the flash directly. All I am using the 600 for is a front fill flash. Not a key light.

[Skirball]

Ahhh, ok.  I see now, I missed that in your original post.  So you're mixing the 600exRT with studio strobes. Are you using the Profoto B1 that has TTL?  What about the Eichrome, does it have TTL?

I don't know much about using studio strobes in TTL mode.  If they're manual I could see that's where the problem lies - mixing manual and TTL.  THe 600ex would first test the power needed without the strobes, think it needs a lot because it's dark, but then when it fires the studio strobes fire boosting up the ambient light. 

There's not going to be any way around that, other than adding a nice even ambient light with the strobes, and then trying to figure out how many stops of light the ambient strobes add and adjusting with a large FEC.  Kinda like what you're doing.

If you use that type of setup a lot you might consider investing in some extra eTTL strobes (they don't have to be 600exRTs) and using them for the ambient as well.

[TCampbell]

Your mixing ETTL and non-E-TTL flashes?  

Ordinarily, if you're going to have manual flashes working then you'd want to put the 600EX-RT into manual mode and control it's power level just like you do for the other strobes.

[rcarvillephoto]

Hey TCambell,

The non ettl strobes have no effect on the overexposing or the 600. They are set to about a stop under my exposure for room a little room light to mimic the actual ambient light that you can't get if you are shooting at those settings. Hope that makes sense.

I took it into a third party specialist two days ago and they told me to send it to canon. They couldn't figure it out. They're must be something broken inside the housing. Also a correction is that on the mkii is when I am having the issue. On the mkiii it works perfectly.

[Skirball]

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@rcarvillephoto wrote:
Hey TCambell,

The non ettl strobes have no effect on the overexposing or the 600. They are set to about a stop under my exposure for room a little room light to mimic the actual ambient light that you can't get if you are shooting at those settings. Hope that makes sense.

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Are they flashes or continuous light? If they're continuous lamps, then yes, it will have no effect on the 600.

But if they're flashes then they will have an effect on overexposing the 600.  The eTTL system on the 600 will test the light conditions without the strobes and decide how much power it needs for exposure, then it will take the actual photo, using the determined power level, but this time the strobes will fire and add in their power to the overall exposure.  Presuming that the 600 correctly determined the exposure level it needed for your subject, it will now over-expose by whatever amount the non-TTL strobes boosted the ambient.

[rcarvillephoto]

Skirball

Yes. I agree with this principal. However it doesn't apply to my set up. The room light (external non speed light strobes) only light the room. They effect they have on the subject is very little. The speed light on camera should exposure for the subject and light them. That is the only purpose for the speed light. The other strobes light background. So there is not crossover to up the initial exposure. I have shot like this for manyany years with no problem. (ie 430ex and 580II ex)

I think there is a hardware issue in the mkii. It has worked in the past but all of a sudden it is doing this. And as I said before the setup works perfect on the mkiii.