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This came up tangentially in another question. A camera's sync speed is the fastest shutter speed for which the first shutter fully opens before the second shutter begins to close. This is important because if the shutter is never fully open, there is no moment for which the flash can expose the entire image.

While the advent of technologies like HSS(High Speed Sync) have allowed taking flash photos beyond the sync speed, they result in much less available flash power. What are the limiting factors that contribute to cameras not having a faster sync speed?

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May be a duplicate of What are the physical limits of a mechanical shutter?, or at least very related. –  dpollitt Oct 31 '13 at 14:55
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@dpollitt - good find, I searched on sync speed and couldn't find anything. I think a more all inclusive answer on that question could probably answer this one as well, but as it currently stands, I don't know that the answers directly correspond. The questions certainly are closely related though. –  AJ Henderson Oct 31 '13 at 15:01
    
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Not quite certain this is an exact duplicate of the potentials offered so far. Ironically, I think one of the reasons, manufacturers simply cheaping our forcing a lower sync to push customers into a higher price bracket for something like true 1/500th sync, hasn't been offered. Past low-end cameras actually used to have higher sync speeds than many do today...I think some low end cameras are 1/180th, when their predecessors were 1/200th, and their predecessors were 1/250th. That certainly isn't a mechanical or construction issue...its a brand bracketing issue. ;P –  jrista Nov 2 '13 at 20:30

2 Answers 2

up vote 8 down vote accepted

The shutter sync is limited simply by how fast the shutter can move in the same way there is a limit to how high a car engine can rev. Increasing these limits increases the demands placed on materials, design and longevity.

Another limit is the distance the shutter must travel (which is determined by the size of the sensor, a full frame shutter has to travel 24mm whereas an APS-C only has to travel 16mm in the same time (this is why some full frame models have slower sync speed).

A way round this limit is to move the shutter from the sensor or film plane to inside the lens. So called "leaf" shutters only have to travel the length of the lens aperture, which is often only a few mm, hence leaf shutters allows substantially faster sync speeds, although sync speed becomes aperture dependant - the wider the aperture the slower the sync.

The final way to break the sync limit would be to move from the mechanical to the electronic domain. Ultra fast electronic shutters already exist, but are expensive and thus reserved for specialist applications.

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By the way, I will mark this as accepted if there isn't another answer soon, I just wanted to leave it open for a bit to see if anyone had any additional insights we haven't covered yet between our two answers. I have a feeling we've probably covered it well though. –  AJ Henderson Nov 2 '13 at 20:36

Certainly one of the major factors is cost and physical limitations of the shutter. A shutter can only move so fast depending on the materials it is made of and the durability of the shutter mechanism.

High Speed Sync has also likely caused less emphasis on a fast shutter sync speed when it comes to design trade offs. Previously, the sync speed was a hard limit for using a flash. HSS might not be ideal, but it still is better than nothing and there are other places that may be able to better use the funds than making a faster shutter (which might also decrease durability.)

Another factor is that since CMOS sensors generally do not support a global shutter, electronic shutters don't work well for cutting off the exposure precisely. Specialized CMOS sensors and most CCD sensors (which aren't used in most, if not all, modern DSLRs) have global shutters which can lead to a second curtain unconstrained by physical speed, but they aren't widely used.

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