BL said:
What exactly gives one DSLR a sync speed of 1/500sec (e.g. a dated Nikon D40/D70, arguably an amateur camera) vs 1/180sec (e.g. Canon's 6D)?
Sensor size? Although I do recall the original Canon EOS-1D having a 1/500sec sync...
If you know, how a focal plane dual curtain shutter works, it becomes fairly obvious: the faster the curtains move, the faster speeds you can achieve without running in slit mode. From a physical standpoint, only light speed is the limit, but for obvious reasons shutters move more slowly. Fast moving shutters were considered a professional feature because they allowed you to shoot with flash in bright light with large apertures. Now idea how the D40 ended up with this feature except for Nikon showing off the beauty of smaller sensors.