Beginner High Sync Speed Flash - Why does it fail?

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Broric

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I'm using a 70D with a YN600EX-RT speedlite.

I'm using HSS and most of the time it work fine but occasionally the shutter will max out at 1/250 and massively over-expose the image. Any idea what causes this? There doesn't seem to be an obvious pattern to it. Turning the speedlite off/on stops it happening for a while but I'm wondering if I'm doing something else wrong?
 
Broric said:
I'm using a 70D with a YN600EX-RT speedlite.

I'm using HSS and most of the time it work fine but occasionally the shutter will max out at 1/250 and massively over-expose the image. Any idea what causes this? There doesn't seem to be an obvious pattern to it. Turning the speedlite off/on stops it happening for a while but I'm wondering if I'm doing something else wrong?
Click to expand...

Pure guess, but while the gun is recharging the camera reverts to normal x-sync and the gun will fire a normal flash during that time. That will be greatly over-exposed even if it's only 3/4 charged. Recharge times tend to be long with HSS because it uses so much power.

Edit: watch the shutter speed in the viewfinder and wait till it changes.
 
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Also your YN600 flashes will beep when charged and ready to fire again.
 
HoppyUK said:
Pure guess, but while the gun is recharging the camera reverts to normal x-sync and the gun will fire a normal flash during that time. That will be greatly over-exposed even if it's only 3/4 charged. Recharge times tend to be long with HSS because it uses so much power.

Edit: watch the shutter speed in the viewfinder and wait till it changes.
Click to expand...
Good lateral thinking and probably right. :) To help speed up recycle times an external battery pack would be beneficial.
 
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