Why can't my camera sync flash at 1/1000s, and is there any flash that will work at that speed?

Asked 3/29/2017

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My camera’s flash sync speed is only about 1/60s. If I set a faster shutter speed, flash exposures are partially dark because the shutter doesn’t fully expose the frame at once. I know old FP flash bulbs could be used with focal-plane shutters at higher speeds, but they are single-use. Is there any electronic flash that can be used at around 1/1000s on a camera with an FP sync port, or is the limit determined by the camera rather than the flash?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

9y ago

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That camera with 1/60 sync (and says ASA) must be at least 40 years old. :) More modern cameras commonly allow 1/200 second shutter with flash.

But this limitation (of not allowing flash with 1/1000 second shutter) is due to the type of shutter in the camera. It is not a property of the flash, electronic or bulb. It is a property of the camera shutter.

Focal plane shutters back in the 1960s were 1/60 second sync, but the focal plane shutters have gotten faster now, 1/200 second sync is common.

There is (or was) a FP sync flash bulb, called FP sync (for Focal Plane), which is a longer burning bulb, which allows any faster shutter speed. The issue is that when faster than sync speed, the focal plane shutter becomes a narrow slit moving across the film. At speeds less than sync speed, the shutter is fully open, which allows flash, even very fast flash. But at faster shutter speeds, it is just a narrow moving slit which is all that gets illuminated by the fast flash. Shutter speed is too fast to sync with flash.

The longer burning flashbulb allows any narrow slit to move, to occur at any point of the slit travel (the longer burning bulb will still be burning there). The faster shutter speed slit does of course seriously reduce the light, you have to open aperture to compensate for the lost exposure time.

In electronic flashes, there is a flash mode called High Speed Sync (HSS), which mimics the longer burning FP sync bulbs, to allow any fast shutter speed. The HSS flash "burns continuously" for the entire shutter slit travel time. It is NOT fast flash, the opposite, continuous like daylight, it cannot stop any motion. But it is High Speed Sync, meaning it does allow any fast shutter speed. Both the camera and the flash have to support HSS, and must be compatible with each other too.

Originally by user38978. Source · Licensed CC BY-SA 4.0

user38978

9y ago

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AI Answer

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The limit is mainly your camera’s shutter, not the flash itself.

With a focal-plane shutter, speeds faster than the camera’s sync speed are made by a moving slit between the shutter curtains. At that point, there is never a moment when the whole frame is uncovered, so a normal electronic flash burst will only light part of the image. That’s why your camera tops out around 1/60s for flash sync.

Older FP flash bulbs worked because they burned long enough for the slit to travel across the film.

Modern solutions are:

  • a camera with a faster normal sync speed (many newer cameras are around 1/200–1/250s),
  • a leaf-shutter camera/lens, which can sync at much higher speeds,
  • or a flash/camera system that supports high-speed sync (HSS), where the flash pulses repeatedly during the exposure.

So, for your current camera, a standard electronic flash on the FP socket will not give true full-frame sync at 1/1000s unless the camera and flash system specifically support a high-speed-sync method.

UniqueBot

AI

9y ago

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