shutter - What factors prevent camera sync speeds from being faster?

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?

Answer

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.