Why do I get black bands when using studio flash above my Canon 600D sync speed?
Asked 12/12/2012
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I’m using two Rekam NEO 200 studio flashes with a sync cable and adapter on a Canon 600D. At shutter speeds around 1/320s and slower, the flashes appear to sync normally. But when I set faster shutter speeds like 1/500s or 1/1250s, part of the frame goes black or the whole image is dark. Is there a way to make these flashes synchronize properly at those faster shutter speeds?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
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That is not a synchronisation problem, that's a limitation of a focal plane shutter, at speeds faster than 1/250s the shutter starts to close before it is fully open, therefore when the flash fires the shutter is not fully open and part of the image wont be lit by the flash, showing up black.
There is very little you can do about this, some flashes are able to pulse very quickly, effectively acting as continuous lightsources, but vastly reducing power output in the process.
Why do you need to use faster shutter speeds? If it is to freeze a moving subject then there is no need as the short flash duration does that for you, up to a point. For this to work the flash must be significantly brighter than the ambient light.
Originally by user1375. Source · Licensed CC BY-SA 4.0
user1375
13y ago
0
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What you’re seeing is the camera’s maximum flash sync limitation, not a fault with the flashes.
The Canon 600D uses a focal-plane shutter. Above its flash sync speed, the second shutter curtain starts closing before the first is fully open, so the flash fires while only part of the sensor is exposed. That creates the black banding, and at very fast speeds the frame can go almost completely black.
With normal studio flashes, there’s usually no way around this. Some dedicated flashes support high-speed sync by pulsing rapidly, but that greatly reduces power and is not typical of basic studio strobes.
If your goal is to freeze motion, you often don’t need a faster shutter speed when using flash. The flash burst itself is very brief and can freeze movement, as long as the flash is much brighter than the ambient light.
So in practice, keep your shutter at or below the camera’s sync speed and control exposure with flash power, aperture, ISO, and ambient light.
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