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I am able to get HHS working on the Canon T6 with the Yonguno flash, but when I go to 1/4000, ISO 100, and f1.8, the picture comes out with a horizontal band that is lighter than the rest of the picture. I can't figure out if this is a defect in the flash, where it is pulsing to many times during the curtain sequence, or something with the camera. Using the Yonguno YN-E3-RT as the trigger.

Playing with settings, even at 1/1000, ISO 400 still getting that lighter horizontal band. When regular on board flash is used, no issues.

Any ideas? Could it be a hardware defect, or am I overlooking something?

  • Do you see the high speed sync indicator in thee viewfinder (flash symbool without the letter "H" at the left bottom side)? – agtoever Feb 15 '19 at 18:30
  • Is the band at the top, bottom, or in the middle of the frame? When you say "regular on board flash" do you mean the camera's pop-up flash (which isn't supposed to be capable of HSS at all) or the YN600EX-RT flash directly mounted to the hot shoe? – Michael C Feb 15 '19 at 19:03
  • Yes, the high speed indicator is on the transmitter LCD and the flash LCD. The band is towards the top of the frame. The on board flash does not fire when using HHS. I used that as an example to show that a "normal flash" photo doesn't have the band. – Chris Feb 15 '19 at 20:12
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If the frame is correctly exposed except for a lighter band, that may indicate an overlap, which might happen if the shutter is delayed in its travel. HSS fires the flash with extremely precise timing in order to make the band produced by the shutter slit at each flash exactly join to the next -- but if the shutter travels faster than the camera's computer expects, you'll get dark band(s) where part of the sensor didn't receive light from the flash, and if the shutter moves slower than expected, you'll get light bands where the flash lighting overlapped on the sensor.

In your case, if you're getting a single light band at 1000 and the same at 4000, it's clear the shutter isn't traveling slow for the whole frame (that would produce multiple bright bands at shutter slit width apart); rather, it's hanging on something at one point.

If your camera body has enough value, it may be possible to have it repaired -- this might be simply due to a foreign object lodged in the shutter's guide groove, or a bent leaf (I'm presuming it's a metal shutter; I've never heard of a cloth one that can shoot at 4000). It might be possible to repair the shutter for less than the replacement value of the body -- or it might not, if the body is more than a couple years old.

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Banding is a classic symptom of the shutter speed being too high for proper flash sync. The flash is firing too late to illuminate the full frame before the shutter closes.

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  • That's the exact condition that HSS is supposed to remedy, by firing the flash multiple times as the shutter slit moves down the gate -- when everything is working correctly, at exactly the right times to give matched, even lighting over the whole frame. – Zeiss Ikon Mar 26 at 18:50

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