Using 540FGZ on K10D

I'm a beginner to flash photography and am confused by the 540 operating manual. It seems to suggest that for general use P-TTL with leading curtain sync is the preferred mode, but it also says the latter can only be used with X-sync or slower on the camera. So that makes me think I should go for High Speed sync, but that can't be used it seems with P-TTL or P-AE mode on the camera. So for GENERAL USE, what is the best combination between the various settings you have to make on the flash and the camera, i.e. (i) P-TTL, TTL Auto, Auto, Manual; (ii) leading, trailing, high speed sync; (iii) P-AE, Sv, Av, X-sync etc. :

For general/beginner use, the best auto combination with the K10D and the AF540 is P-TTL, leading curtain sync (the default), and Program mode (or X).

Better even than that is fully manual, until you've got your head round how it all works, because then all the things that affect whether or not your photograph is correctly exposed will at least make sense, even if (like me) you can't remember to bear them all in mind all the time.

All the X-sync speed is, is the shortest exposure (that is, the fastest shutter speed) for which the shutter is completely open for the whole exposure.

Therefore the flash, whose duration is far, far shorter than that time, will illuminate the entire frame, while the shutter is open.

Only if you absolutely have to have a shorter exposure than this, do you need high speed sync, in which mode the flash emits a burst of flashes during the transit of the gap between the shutter curtains across the frame.

(If this is not entirely clear to you, it might be an idea to read up on how focal plane shutters work, in particular at exposures shorter than the X-sync speed, since not much will make sense unless you understand this.)

The sections in the K10D manual on flash photography are also worth reading, despite the fact that it's now slightly out of date since Pentax introduced some new features with recent firmware releases, notably the ability to use the built-in flash as a wireless master.

And read Matt's excellent article here.