Originally posted by jon.partsch Yeah, I really don't get it either. The shutter is definitely the thing that limits sync speed. Flash strobe duration is usually somewhere between something like 1/50,000 sec for preflash and fill flash in some applications to 1/1000 sec for full flash. There is no reason the strobe unit should have an impact on sync speed. The rumored 1/180 or 1/250 sync speed with certain strobes on the K-5 sounds like a firmware trick to force us to buy more expensive P'tax brand strobes if we want the 1/250 sec sync speed.
My conjecture is, shutter speed is one of the things, but not the
only thing that limits sync in a modern system. With a TTL flash, you're doing more than simply communicating the sync signal. And while it's a valid point that if higher speed was available why would they make it available, here's just as valid of a question: Why go through the trouble of disabling the center pin above X sync? That's a SW choice, and it makes me think that it works, just not as consistently as they wanted. Maybe some comm or timing issue when they were making the P-TTL system. Maybe that's why it's not super consistent? And rather than fix it initially, they slowed down the com, said, "1/180 is max", giving the system plenty of buffer time, and called it a day. Maybe that why new flashes are required to exploit it? Maybe (probably) this is all wrong.
Pocket Wizard had a chart on their site showing Canon's flash system, and how much slop there was in the timings, even at a higher sync speed, and how they're wringing better efficiency out of FP sync on that system with more precise timings. That also makes me think Pentax can do a lot with SW tweaks.