I remember reading the higher flash sync is better achieved on the crop sensorsHaven't heard any rumors, but the 1D X only manages 1/250 s, same as the 1DsIII. I think the 5DIII will stay at 1/200 s.
Strange the 1d4 is 1/300 - usefull for the 70-200 on a 1.3
I don't believe this argument. If it was better achieved on the crop sensors, then why did the EOS 1, EOS 1n, and 1V all have 1/250 sync speed? If I am mistaken, I apologize but these are film cameras so the full frame versus crop sensor frame reasoning seems odd to me. If the argument of crop sensors only achieving this sync speed, then they would all have sync speeds of 1/200 or possibly less. Could you explain further why 1/250 worked on a film camera but only full frame digital cameras only allow 1/200?