Trailing flash using built in flash on K5

Hi there,
has anyone used the built in flash on the K5 on trailing flash setting?
Been trying out new things recently and this was one of them.
Is it correct that the flash fires at both the beginning and end of the exposure? Focusing had already been done, was using self timer, pressed shutter release, when exposure started - flash - at end - another flash.
No mention of this in hand book. Has anyone else noticed this?
Thank you in anticipation

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Pentax K5,Sigma 10-20 f3.5,Sigma 17-70 f2.8/4, Sigma 70-200 f2.8

I'm only guessing, because I don't have a K5, but are you sure that the shutter was open when the first flash fired?

Often the built in flashgun fires a kind of 'testing' pre-exposure flash just before the shutter opens. It helps set up flashgun power and other things. I know that it is a damn nuisance when one wants to use a weak flash from the camera's own source in order to trigger a remote flash on a slave adapter: the slave flash gets triggered just before the shutter opens!

Try photographing a moving object (maybe a stopwatch) with a longish shutter time, and see if you get one or two images.

Just a guess!

Martin

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A few of my photographs in flickr.
Lizars 1910 "Challenge" quarter-plate camera; and some more recent stuff.

In P-TTL mode, there is always a preflash. The camera determines the proper flash power from the info it gathers during the preflash. In order to see the second flash, the camera needs to be set on 2nd curtain flash, and you need to use a rather long exposure. In regular mode, the preflash and actual flash are so close to each other, the eye "sees" only one flash.

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Yves (another one of those crazy Canucks)