BetterPhoto Q&A
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Flash Sync

I just need to find out how a focal plane shutter works when using flash with one select a shutter speed that is higher than 1/60 sec. As previously a focal plane shutter can only sync at 1/60 sec. but now most camera sync at 1/250 sec. Is it because of a different type of shutter use or is it because of a more advance flash unit that make it possible.
From what I know, at higher shutter speeds the second shutter starts moving before the first shutter has fully open up thereby creating a slit.
So I was wondering whether previously at 1/60 sec. the first shutter was able to fully open up before the second shutter starts moving. But now there have created a shutter whereby the first shutter was able to fully open up before the second shutter starts moving at a speed of 1/250 sec. Or is it because of the flash?
Please enlighten me on this.
It would be very much appreciated.

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January 11, 2001

The flash sync speed for a focal plane shutter is the fastest speed at which the shutter is fully open on the full film frame. For most SLR's it is between 1/60 and 1/250. At higher shutter speeds the first and second curtain of the focal plane shutter form a small slit that moves across the film frame. The duration of the flash of an electronic speedlight is only about 1/10,000 second. If the shutter speed is higher than the flash sync speed, then the flash will affect only that small slit opened on the film when the flash fires.

The flash sync for most entry-level autofocus SLR's is 1/90. It's usually 1/125 for mid-level SLR's and 1/200 or 1/250 only on professional models.

Note that point-and-shoot cameras can flash sync at any shutter speed because the shutter is combined with the aperture (leaf shutter) rather than a focal plane shutter.

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January 14, 2001