Why do I get a bright band and underexposure when using a bounce flash in E-TTL on my Canon DSLR?
Asked 12/16/2019
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2 answers
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I’m using a Canon EOS 1300D with a Neewer 562C flash. At 1/60s, f/9, ISO 800, the flash exposes normally when pointed forward in E-TTL, but when I tilt it up to bounce off a white ceiling in E-TTL, the frame is badly underexposed and shows a bright horizontal band near the top. In manual flash mode, bouncing at about 1/16 power gives a normal-looking result. I also tested the flash off-camera and saw the same behavior. At 1/40s and 1/80s the bright band disappears, but the image is still very underexposed; at very slow shutter speeds the frame is brighter overall but blurry. What could cause this?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
6y ago
2 Answers
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You can see the "bar of odd exposure" on your second image, too: it starts at the bluish disk above the "Star Wars" tool on the left. I don't see it in the first image without flash though it should be on-frame and I don't see it in the last image. The "straight-up" bounce shows a white clock face in that bright stripe, and it would appear that the clock face is more or less exposed correctly.
The camera is a DSLR. My personal guess would be that you have a shutter and/or mirror problem. The camera is probably not entirely new, and you may be getting a bit of the preflash exposure added to the top of the sensor.
Originally by user88491. Source · Licensed CC BY-SA 4.0
user88491
6y ago
0
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This points to a flash/camera timing problem rather than normal bounce-flash behavior.
The bright band suggests the flash is firing when the shutter is only partly open, so only part of the sensor gets the flash exposure. That’s why you see a correctly lit strip while the rest of the frame stays dark. Your slower-speed tests support this: with more ambient exposure the image gets brighter, but blur increases, which means the flash isn’t syncing at the right moment.
Because it happens with the flash on- or off-camera, and manual flash can look usable, the likely issue is mis-timing between the camera and flash in E-TTL/sync, or possibly a camera shutter/mirror fault.
In short: this is not expected from simply bouncing off a white ceiling. Try confirming with another known-compatible Canon flash or another camera. If the problem remains with other flashes, the camera may need service. If it only happens with this flash, compatibility or triggering timing is the likely cause.
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