I've set up a studio with two Profoto B10X on either side with soft boxes, however, I keep getting a light bar at the left edge of the frame on my images. It happens on the the same side every time, it just moves depending if I'm shooting landscape or portrait.

I've tried adjusting my shutter speed 1/100 1/125 1/160 as thought it might be to do with that but it stays the same. It doesn't show with natural lighting, or on camera flash only with external lights.

I use a Canon R5 and it is 1 1/2 years old. I have tested using different lenses, prime and zoom but still get the same issue.

Any ideas why this might be happening?

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  • 2
    Did you test you camera without any artificial lighting (go outside and find a white wall)? Looks like a shutter problem to me.
    – xenoid
    Mar 20 at 7:47
  • 3
    @ZeissIkon if the problem doesn't show outside of the studio, I have no answer :)
    – xenoid
    Mar 20 at 12:57
  • 1
    We need more information -- starting with what camera you're using to make these images. This looks like a focal plane shutter issue, but the orientation of the strip is wrong for the common ones.
    – Zeiss Ikon
    Mar 20 at 13:41
  • 1
    @Zelly Okay, Canon R5 -- now please edit that information into the question so it stays available after these comments are deleted. Also, it would be helpful to know what shutter speed (range) this occurs in. It looks like the kind of thing that could happen with a mis-triggered multi-flash for high sync speed...
    – Zeiss Ikon
    Mar 21 at 11:08
  • 1
    The Canon R5 offers three shutter modes: mechanical, electronic first curtain (EFCS) and electronic shutter. Which shutter mode are you using? Mar 21 at 19:26

2 Answers 2


It appears that you're using camera's mechanical shutter, and that your strobes are dumping all their power in a short amount of time (about 8 times faster than your shutter speed, roughly).

As the shutter opens, it exposes the top of the sensor first, and travels downwards. Before the shutter is even 1/8 open (roughly), the strobe is done. The shutter is exposing the remainder of the sensor to a scene that isn't being lit by the strobe.

Note that the bright stripe at the bottom of the image corresponds to the physical top of the sensor, because the image projected from the lens is inverted vertically and laterally onto the image. This is how all images are projected through a lens.

  • Mechanical focal plane shutters have a "sync speed" which is usually at least 1/125 on modern equipment (can be as high as 1/250 on top end gear). If you're at or below sync speed, the flash is triggered when the first curtain reaches end of travel, and before the second curtain starts. This will illuminate the entire frame evenly. You may want to edit in a mention that a slower shutter (than 1/125) will likely improve this strip.
    – Zeiss Ikon
    Mar 22 at 14:57
  • T0.1 flash durations are faster than x-sync shutter speed, and T0.5 are about 3x faster yet... flash durations≤ 1/4000 are common. Plus, there's a long flash tail that would prevent a hard line like this. Mar 22 at 15:26
  • @ZeissIkon OP edited their post that they tried 1/100. Also, the Profoto B1 strobe is capable of HSS
    – scottbb
    Mar 24 at 1:03
  • 1
    @StevenKersting I'm not sure I agree it's a "hard" line transition. IGBT-controlled strobes have a pretty short tail
    – scottbb
    Mar 24 at 1:04
  • 1
    Seeing as how the OP hasn't commented since 3/20, I'm going to go out on a limb and guess the OP discovered the trigger was set to TTL with the flashes set to manual power and it was kicking the B10Xs with the pre-exposure metering flash?
    – Michael C
    Mar 25 at 2:51

I'm guessing the R5 shutter travels from bottom to top of the mirror box; which is top to bottom of the image.

That looks like shutter bounce; the shutter bounces back open slightly resulting in a band of overexposure at the end of the exposure. It might need repaired...

EDIT: If the shutter travels from top to bottom instead then the only thing that makes any sense is a very early high speed sync timing.

In (true) high speed sync the flash pulses continuously to act as a constant light source and then it turns off. It is also running at a lower power with a shorter duration and a much shorter tail (T0.1). If the lights are turning off at the beginning of shutter travel you could get this type of effect

  • Wouldn't you expect to get the same effect in the other lighting conditions that the OP has tried and doesn't get that effect?
    – Peter M
    Mar 21 at 0:52
  • @PeterM, Not so much... flash adds a lot of light in a very short amount of time, so a quick re-exposure can compound the exposure significantly. Most ambient exposures it would show much less or not at all. The studio strobes probably have a lot longer/more powerful tail than the pop-up or speedlight. Mar 21 at 3:04
  • This looks a lot like a triggering problem. And I see the R5 is mirrorless, though, so no physical shutter at all.
    – Zeiss Ikon
    Mar 21 at 12:19
  • 1
    @EricS I'll take your word for it. If so, they're probably based on DSLR shutters which in turn are based on the last generation of film SLR shutters, which ran top to bottom, universally.
    – Zeiss Ikon
    Mar 21 at 18:15
  • 1
    @StevenKersting Right. So the bright line is at the start of shutter travel, not the end, so isn't shutter bounce. Mistriggering a multi-fire flash (the kind that lets a shutter with 1/125 or 1/250 sync speed use flash at 1/4000) could result in double flashing one stripe...
    – Zeiss Ikon
    Mar 22 at 11:03

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