High speed sync on AF540FGZ

Do we have any users amongst us using the above flash. Just been reading my manual for the Pentax AF540FGZ but find it a little confusing. I was researching High speed sync. Which I understand to a point. But I would have preferred to use it in manual mode. Though it seems it can only be used in P-TTL mode. Is this correct? Also It cant be used in this mode off camera it seems. Why ? Can anyone enlighten me..? No pun intended..

Hi Stub
For HSS to function the flash needs to operate in P-TTL. When you take the flash off camera, the HSS does not function unless you use a TTL lead. If you want to use P-TTL wirelessly, the only way to do it that I know of, is the Aotek trigger.

IIRC you can do wireless P-TTL HS when using an AF360 or AF540 as a master controller on the camera and one or more slaves.

My understanding is it's primarily due to the way HS has to work - by 'peppering' the frame with smaller bursts of light as the shutter curtain moves down the frame. The only pop-up that could do HS wireless was on the *ist-D. (Somewhere I read that the bursts of energy and resulting electrical noise on the power rails on the flash caused problems for SR - who knows!)

You can use manual camera exposure with P-TTL flash though and that does give a modicum of control

Matt

Thanks for the replies lads.. Looks like I could be struggling

What is the concrete challenge?

There is unfortunately no way around using a P-TTL flash connected to the camera (on the hot-shoe or using a cable), but you could use a Cactus V6 (or Cactus RF60) to optically trigger on the P-TTL flash and thus gain a radio trigger signal from the HSS flash.

You are then free to trigger as many off-camera flashes as you like. The Cactus RF60 offers an HSS sympathy mode that achieves HSS bursts for all manual levels, but you can also use pretty much any flash at full power because with most speedlites at full power the pulse is long enough to illuminate the whole frame.

Not strictly true, P-TTL is disabled when a pre-A series lens is used.

I'm not sure what you are objecting to.

Please note that my statement was made in the context of using HSS, i.e., the camera is using a shutter speed higher than 1/180s.

In such an HSS situation, the only way to obtain a trigger signal is optically from a P-TTL flash connected to the camera.

If a pre-A lens disables P-TTL then even that triggering opportunity is gone and in this case you cannot use flash beyond 1/180s at all.

I wasn't objecting to anything. It is however possible that I misinterpreted the meaning of your statement. Whether that was due to how it was written or my reading it incorrectly, who knows.