(Moved here from chat) I faced a trouble with my Canon 6D and a Canon SpeedLite 430ex II...

I took some shots and here is the result I've had : enter image description here

I've used the very same shutter speed as I was using on my previous camera, a Canon 450D. I was using 1/250.

It looks like I have some shutter/curtain problem, such as them closing too quickly and I can see them on the picture (something related to this)... I therefore tried to decrease my exposure speed to 1/160 and then it worked perfectly...

I'm a bit confused by this tho...

  • How can my 450D be better than my 6D ?
  • There should be a compromise that Canon did regarding that parameter but I have difficulties to understand properly the whole concept...

I mean, since my flash is powerful, I could simply get slower, it probably won't change the exposure of my scene. But,... If I'm using a long lens, let's say my lens has a focal of 400, I'm using a flash and for some reason I want to handhold it (probably stupid example but let's pretend)... I need a shutter speed that is faster than 1/400 or I'll get blur because of my hands shaking... If I cannot go faster than 1/180 (I've found this value as maximum shutter speed synchronisation for my Canon 6D), how will I manage to do that ?

  • Also could be your shutter sticking Jul 14, 2014 at 12:06
  • @ElendilTheTall Oh yeah, looks like a duplicate of your link... However, is there a way to check that it is indeed not my shutter sticking (it's unlikely i guess, the camera is two weeks old)...
    – Andy M
    Jul 14, 2014 at 12:19
  • I'm not convinced this is absolutely a duplicate - in general, you shouldn't be able to set your shutter to faster than the sync speed (unless you have HSS enabled). If you're able to set the shutter speed to faster than 1/180s, I think something else is going to a bit wrong.
    – Philip Kendall
    Jul 14, 2014 at 12:33
  • 1
    OK, definitely not a duplicate in that case :-)
    – Philip Kendall
    Jul 14, 2014 at 14:23
  • 2
    It is a duplicate - the sync speed of the 6D is 1/180s, shoot faster than this and you'll see the shutter curtains. Case closed.
    – Matt Grum
    Jul 15, 2014 at 12:54

1 Answer 1


At 1/250, you are trying to exceed the x-sync speed of the 6D (which is 1/180, as you have found), which explains the black bar.

Don't forget that on the 450D, as a crop-sensor camera, the shutter has less distance to travel, so doesn't need to move as fast to give the same exposure time, which explains why some full frame cameras have a slower x-sync speed than crop sensor models.

The only way to get your shutter speed to the 1/400 you suggest as an example would be to use high speed sync (HSS) flash, to allow you to shoot faster than the x-sync speed, though you might struggle with how far out the flash will reach with HSS enabled.

  • Or you could shoot at 1/160 with a tripod.
    – Michael C
    Jul 15, 2014 at 3:56
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    Plus using flash as the primary light source for a scene (like in the example) will mean the exposure time will in practice be the flash duration and not the shutter time so going for a slower shutter and disabling HSS should give a sharper result due to the shorter flash duration. Jul 15, 2014 at 9:08
  • Basically what @JamesSnell said. It's worth noting that with the Canon 430EX (and similar speedlights) reducing the flash power also reduces the flash duration, making it better at freezing motion (but make sure you're still able to overpower the ambient light or you'll get blur).
    – Matt Grum
    Jul 15, 2014 at 12:58

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