Problems with flash guns and Canon 7D

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tms789

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Hi

I have a 7D and two flash guns a Marumi ring flash and a 430EXii. Most of the time these flash guns both work perfectly but occasionally I get black photos depsite the fact the flash has fired. Looking at the histogram there is a very brief peak at the very left hand edge but nothing at all afterwards.

Any ideas please?
 
Oh yes the flash definitely goes off. The camera is set to manual and it is not working off any trigger only the shutter.
 
Should have added the flashes are seated in the hot shoe not off camera.
 
Are you using a shutter speed below 1/250?
I can't remember if it'll force a slower one in manual with a flash on the hot shoe or not but the speed needs to be below that for the flash to sync (unless it's in high speed sync mode).

Is there any pattern to when it fails to expose or is it completely random i.e. if it fails and you try the exact same shot with the same settings again will it then decide to work?

When you get a failed shot do you get the little green light on the back of the 430EX II?
 
Hi Dazjw

Shutter speed set at 1/125.

No noticable pattern - it seems to have a mind of its own. Sometimes I get 5 to 10 black photos in a row and then it suddenly works properly sometimes it works straight away. I don't change settings just keep clicking the shutter.

Little green light works when photo is correctly exposed when the photo is black no green light appears. As this happens with two flash guns I have rulled out error with flash guns ETTL etc.

Somewhat puzzled as there seems no logical explanation and would like to resolve so I don't miss good shots.
 
Are you firing off shots quicker than the flash/batteries can keep up with ?

What power/distance are the shooting at?
 
No i am not firing photos off too fast. Distances vary the marumi is a ring flash so this is macro work the 430 varies from 5 to 12 feet.
 
tms789 said:
No i am not firing photos off too fast. Distances vary the marumi is a ring flash so this is macro work the 430 varies from 5 to 12 feet.
Click to expand...
It would seem from the quote below that you're shooting before the flash has recycled. The flash isn't ready to fire till the light is on.
tms789 said:
Hi Dazjw

Shutter speed set at 1/125.

No noticable pattern - it seems to have a mind of its own. Sometimes I get 5 to 10 black photos in a row and then it suddenly works properly sometimes it works straight away. I don't change settings just keep clicking the shutter.

Little green light works when photo is correctly exposed when the photo is black no green light appears. As this happens with two flash guns I have rulled out error with flash guns ETTL etc.

Somewhat puzzled as there seems no logical explanation and would like to resolve so I don't miss good shots.
Click to expand...
Either that's a recycling problem (your firing rate) or your batteries. IMO it's a very logical explanation. You can't fire the flash before it's ready. From a full charge it's good for a small burst (depending on conditions) but until it's ready it won't fire.
 
Phil V said:
It would seem from the quote below that you're shooting before the flash has recycled. The flash isn't ready to fire till the light is on.
Click to expand...

Phil I think you're misunderstanding which light I asked him about. It's not the ready light, it's the green successful exposure light.

tms789 said:
No noticable pattern - it seems to have a mind of its own. Sometimes I get 5 to 10 black photos in a row and then it suddenly works properly sometimes it works straight away. I don't change settings just keep clicking the shutter.

Little green light works when photo is correctly exposed when the photo is black no green light appears. As this happens with two flash guns I have rulled out error with flash guns ETTL etc.
Click to expand...

If it's happening with two different flashes it suggests the issue is with the body so trying to get hold of another one to test with would be handy. I'd try it with a different lens too just to eliminate that.

If you can't get hold of another body, or if you can and you find the flashes work fine on that body, I think it's a case of write down everything you've done to test it and get in touch with Canon.
 
I have come across the problem I think.

In a few-hundred possibly pictures that I have taken with the 7D and the 580 exII attached directly on top, there have been 3 or 4 where the flash has activated, but the image is extremely under exposed.
The picture prior, and the picture after are both OK. The flash appears to be normal power for the situation, and there has been 5+ seconds between shots (more than enough for a recycle usually, as I don't tend to use the batteries when flat).

It just appears that for me, on a couple of occasions, the flash has happened at a different time to the activation.

For me, it is not common enough to try and get a service, as it is hobby pictures I can live with it. If it were paid portraiture work then that would be different.
 
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