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Canon EOS 550D on LiveView produces 2 exposures

 
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MacroB



Joined: 15 Nov 2010
Posts: 79

PostPosted: Thu Mar 19, 2015 10:46 am    Post subject: Canon EOS 550D on LiveView produces 2 exposures Reply with quote

Hello All,

Have just got the camera out ready for arrival of the Diptera with Spring.

When camera set to Manual & speed at 1/250th using a PocketWizard PlusX transceiver to fire an Einstein 650 studio flash I get 2 exposures in Digital Photo Professional. The first exp is black and the second is a normal flash exp. I am triggering the camera on PC monitor via EOS utility.

Have tried using the EOS 550D inbuilt flashgun to fire the Einstein, which drops the speed to 1/200 but then produces ONE perfect exposure instead of the 1 blank and 1 normal.

Unfortunately the size of normal photo stacks would, I'm sure, burn out the inbuilt flash, which was the reason for buying the Pocketwizard.

Mirror lock up is enabled and it is almost as if the first blank exp is when the mirror goes up.

If some kind sole can see what's happening I would be most grateful.
Best wishes,
Bob
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Charles Krebs



Joined: 01 Aug 2006
Posts: 5564
Location: Issaquah, WA USA

PostPosted: Thu Mar 19, 2015 12:01 pm    Post subject: Reply with quote

Bob,

Could you clarify something...

Quote:
I am triggering the camera on PC monitor via EOS utility.

Quote:
Mirror lock up is enabled


When you trigger the camera is it in "live view" mode (as would be suspected if you are using a PC and the EOS utility).

Unless you are using a Canon "dedicated" flash (or internal flash) no flash sync signal is given by the camera when it is triggered while in "live view", so the Pocket Wizard would not fire. (Somehow I suspect this is related to your problem).

As far as I know the "mirror lock-up" custom function does not really do anything from "live view" (the mirror is already up). It is useful when the camera is not in "live view" mode, and then two release signals are needed... one to flip the mirror up, and a second to trip the shutter.

I'm not familiar with the Pocket Wizard units, but getting two exposures (one "black: one with the flash) is puzzling.
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MacroB



Joined: 15 Nov 2010
Posts: 79

PostPosted: Fri Mar 20, 2015 10:14 am    Post subject: Reply with quote

Hello Charles,

Thought it might be the MU causing the trouble so worked through all the other possibilities. Unfortunately that did not make any difference so it looks as if it will not fire studio flash while in LiveView.

Have emailed PocketWizard to see what they suggest. Ten to one it will mean an upgrade.

Many thanks for responding it's always good to know there is someone out there when things don't work.

Best Wishes,
Bob
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Charles Krebs



Joined: 01 Aug 2006
Posts: 5564
Location: Issaquah, WA USA

PostPosted: Fri Mar 20, 2015 11:43 am    Post subject: Reply with quote

Quote:
it looks as if it will not fire studio flash while in LiveView

No Canon cameras with electronic first shutter curtain will provide a flash sync signal while using the electronic first curtain. In the Digital Rebel series this is always the situation from live-view as EFSC is always used from live-view.

With higher end Canon models you can turn off EFSC. Then, what happens from live-view is that the shutter's mechanical first curtain closes and immediately re-opens, and an appropriate flash signal is given. With the Digital Rebel series, if the camera senses an active dedicated flash attached, it will then abandon the EFSC mode and do the same thing, also providing a sync signal.

Quote:
Have emailed PocketWizard to see what they suggest. Ten to one it will mean an upgrade.

I doubt there is anything they can do if since there is no flash-sync signal is given from live-view with your camera unless a Canon dedicated flash is used.

My "work-around" has been one of two methods. Optically slave the main flash. Use a Canon dedicated flash on the camera (or attached via a dedicated cord). Set the flash to very low manual power setting (like 1/64 or 1/128... batteries last a LONG time and no real concern about overheating flash). This way the camera will turn off the EFSC and cycle the mechanical first shutter curtain... and provide the signal to the Canon flash... which then triggers the main.

When you are not using live-view), you can use the mirror-lock up custom setting and provide two release signals to the camera. The first flips up the mirror, the second releases the mechanical shutter (with flash sync signal).
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rjlittlefield
Site Admin


Joined: 01 Aug 2006
Posts: 17395
Location: Richland, Washington State, USA

PostPosted: Sat Mar 21, 2015 11:52 am    Post subject: Reply with quote

MacroB wrote:
When camera set to Manual & speed at 1/250th using a PocketWizard PlusX transceiver to fire an Einstein 650 studio flash I get 2 exposures in Digital Photo Professional. The first exp is black and the second is a normal flash exp.

Charles Krebs wrote:
but getting two exposures (one "black: one with the flash) is puzzling.

I think I can explain this apparently bizarre behavior.

On my T1i (500D), when I shoot in Live View there is a short interval following each exposure during which the camera mechanics are not in Live View.

If a second exposure is taken during this short interval, then the external flash triggers just as it would if the camera had not been in Live View to start with.

I think MacroB is describing a situation in which Mirror Lockup is ignored in Live View mode, so the first shutter pulse takes a picture instead of just raising the mirror which was already up, and then a second shutter pulse arrives during the critical interval, triggering both a second exposure and the external flash.

As far as I can tell, this behavior is not actually related to Mirror Lockup at the hardware level, but it can appear to be from the human's standpoint because two shutter pulses close together is standard operating procedure in Mirror Lockup mode.

--Rik
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MacroB



Joined: 15 Nov 2010
Posts: 79

PostPosted: Tue Mar 24, 2015 8:26 am    Post subject: Reply with quote

Thank you Charles and Rik,

Was already using the 430EXII flash at 1/64 to trigger the Studio flash but wanted to cut down on the stray light flashing about.

Have returned the PocketWizardPlusX transreceivers and will contend myself with a snoot on the studio flash.

One usefull thing has come out of this - I now realise I do not need to enable Mirror lockup in LiveView!

Thank you for yor help and info.
Best wishes,
Bob
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pierre



Joined: 04 Jan 2010
Posts: 224
Location: France, Var, Toulon

PostPosted: Tue Mar 24, 2015 10:56 pm    Post subject: Canon EOS 550D on LiveView produces 2 exposures Reply with quote

Hello,

Have you try using flash on 2nd curtain?
It works using LV
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Pierre
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MacroB



Joined: 15 Nov 2010
Posts: 79

PostPosted: Wed Mar 25, 2015 1:27 am    Post subject: Reply with quote

Hello Pierre,

Thanks for the suggestion but have sent the PocketWizard back now.

I did not have any trouble with the Canon flash on camera setting off the studio flash. It was just a case of wishing to cut down on use of flash.

One good thing is that not having to worry about MU in LiveView it will speed things up just a bit.

Best wishes,
Bob
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