I think I am having shutter issues with my 5D mark iii. image is vignetting on top of frame.

[DanielZenker]

I think I am having shutter issues with my 5D mark iii. image is vignetting on top of frame. ( left side when shooting portrait).

does not happen all the time. shoot 20 frames, not a problem then will happen 4 or 5 in a row or every other shot for a few shots.

Studio situation with 4 lights but it is not a light issue. subject is dark also. all lights fire at full.  happens weather at 1/100 or down to 1/20. these 4 examples were shot at 1/50  f 10 iso 100. raw converted to jpeg. shooting teathered but I dont think that matters. has anyone else had shutter issues? can any one from canon give me any info or help??

[TCampbell]

It may be that the flash is firing as the shutter is opening... but if you're having an issue with a sticking shutter, the shutter isn't completely open when the flash fires.  

If this is the case then it wouldn't matter how long the shutter is open because the flash doesn't provide light continuously when the shutter is open... it only gives a burst.  That momentary burst is normally fired at the moment the shutter finishes opening up completely (but if the shutter is sticky and isn't completely finished opening when the flash fires... you'd have a dark edge.)

If you used 2nd curtain shutter so that it doesn't fire until the moment before the shutter is intended to close, you shouldn't see vignetting even if the shutter is sticking.

But this makes me wonder what the shutter count is on your body and if it needs service.

[Skirball]

The second pic certainly looks like curtain obstruction with flash (left side).  Both have the vignetting on the upper right, are all pics like that?  The subject looks similarly exposed to me.   It's hard to put a finger only on the shutter when you're using a 4 lighting setup, too many variables.  1/50 is far too slow to catch a curtain in a properly functioning system, but I don't know what triggers you're using.    If it's happening that frequently I'd recommend shooting some pics outdoors, on a tripod, in natural/continuous light and see if you can repeat the condition.

[DanielZenker]

currently using Pocket wizards to set off main light and built in slaves to trigger other 3 lights. went back in studio and set up hot lights and shot at many verious shutter speeds and no problems. Im thinkng its some type of shutter sync issue. the camera itself is less then a year old so I dont feel there should be a shutter count issue.

[Skirball]

That's good to know, and not totally surprising.  Next step is to narrow down exactly what is causing the issue.  What do you mean by built in slaves?  Are you using an optical trigger?  If so, that's probably where I'd look next.   I'd eliminate the optical trigger and see if that fixes it.  Otherwise I'd look to the PW.  Though hitting a curtain at 1/50 is really slow.  Hopefully there isn't something amis with the 5d3's timing.