5D flash sync limit with flash turned off

[uscpsycho]

I recently encountered a frustrating situation with my 5DmkIII and 600EX flash.

Like an idiot I didn't check my flash batteries and realized they were dead when I tried using the flash. However, even with dead batteries the camera was limiting my shutter speed to 1/200. Same situation with the flash power turned on and off, shutter speed limited to 1/200. Remove the speedlite from the camera and everything is back to normal, put it back on the camera and shutter speed again limited to 1/200 (even with flash power in off position).

After charging the same batteries there is no shutter speed limit when the flash is powered off and attached to the camera.

Is there some reason why my camera would limit the shutter speed when a flash with dead batteries is on the camera?

[diverhank]

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@uscpsycho wrote:

I recently encountered a frustrating situation with my 5DmkIII and 600EX flash.

Like an idiot I didn't check my flash batteries and realized they were dead when I tried using the flash. However, even with dead batteries the camera was limiting my shutter speed to 1/200. Same situation with the flash power turned on and off, shutter speed limited to 1/200. Remove the speedlite from the camera and everything is back to normal, put it back on the camera and shutter speed again limited to 1/200 (even with flash power in off position).

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Strange...I need to test this with my 5DIII tonight.  Last night I was shooting with a mounted flash on my 7DII and it didn't behave this way.  With the flash mounted but turned off, there was no speed restriction.

 I can understand that with the flash turned on - even with dead batteries, the camera still sees it as flash on.  The batteries may be low enough not to fire but there is still some power in the system.  What I don't get is with it turned off and the camera still thinks the flash is on.  

In many cases I mount the flash on my 5DIII camera all the time without turning it on. I can't recall running into this problem.  I'll report tonight or later when I have the camera to test it with.

[uscpsycho]

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@diverhank wrote:

Strange...I need to test this with my 5DIII tonight.  Last night I was shooting with a mounted flash on my 7DII and it didn't behave this way.  With the flash mounted but turned off, there was no speed restriction.

I can understand that with the flash turned on - even with dead batteries, the camera still sees it as flash on.  The batteries may be low enough not to fire but there is still some power in the system.  What I don't get is with it turned off and the camera still thinks the flash is on.  

In many cases I mount the flash on my 5DIII camera all the time without turning it on. I can't recall running into this problem.  I'll report tonight or later when I have the camera to test it with.

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Test this with dead batteries if you have any. If I'm using charged batteries in my flash then my 5DmkIII does not limite shutter speed if the flash is turned of. Just like your 7D. The strange thing is with completely dead batteries my camera limits shutter speed even when the flash is on or off.

I do not have any more dead batteries but I just tried to replicate this behavior with no batteries in the flash and the camera acted as one would expect - no shutter speed limitations whether the flash was on or off. So there is something specific to having dead batteries in there.

On the day in question, when I had dead batteries in my flash, I was able to replicate this several times by taking the flash off my body and putting it back on. Each time I put the flash on my camera with the flash turned off, my shutter speed was limited to 1/200. It's not like this was some bizarre one-time ocurrance.

[diverhank]

I tested on my 5DIII and with the flash mounted but turned off, it does not get limited.  I had 1/500 and it stayed there.  As soon as I turned the flash on, Tv went to 1/200.  Turned it off, the Tv went back up to 1/500.  This was how I remembered it and that how it worked on mine.  Not sure what happened to yours.

I don't have any dead batteries sorry so no test but as I stated earlier...dead batteries are relative...there may not be sufficient charge to power the flash but there is still enough juice to tell the camera that the flash is on...no surprise there.