K5 built in flash

Hi Matt. That pretty much sums up what I think is going on and for any serious flash photography then i'll look at a separate flash anyway. It feels a bit frustrating though that i've discovered with my day old camera that I may have to use a p&s for indoor snapshots rather than the K5.

Looking at the menus it seems as though there's a specific setting for controlling other flash units wirelessly but maybe even on the standard setting there's something like you describe going on.

Oh well, this is the Pentax User Forum. You can always be sure an expert will be along in a minute.

In my own defence, I dont use the on board flash but usually studio flashes so I'd forgotten one of the reasons I eschew the built in firework display.

Thanks to everybody for your comments and help.

There is possibly one other explanation.

Many years ago I had a Zenit camera that had a knob which selected X (electronic flash) and M (flash bulb), if I remeber correctly.

Anyway if you left it on the M setting the picture was black as the electronic flash had already gone off. By sliding the knob around tpwards the X the amount of exposed film was reveiled, an going past the X meant the flash was too late.

Sorry for the ramble, but is it possible that the electronic flash on the K5 goes off towards the end of the 1/180th of a second and the 7D towards the begining of the 1/180th ie say 1/500 sec earlier.


regards
Bernard

You have the choice of leading or trailing curtain on the K5 (trailing = "Slow")

However, in both cases there is still the pre-flash which is what makes people blink!
Matt

Hi Bernard. I suspect that's exactly what is going on, based on the fact the flash duration is shorter than the flash sync shutter speed.

The more I've tested it the more it's frustrated me. Pentax Tech Support (087...) said "update the firmware and try it again, in the mean time we'll get back to you in a few days..."

Lovely camera. Lovely IQ - I just need to decide if I can live with the 'quirk'!

The flash duration will always be shorter than the given flash SSS - the actual duration of a flash is from around 1/500 sec to 1/30,000 sec.

You may be able to solve this problem with a simple diffuser or alternatively a snoot to direct the flash onto a ceiling or a wall. The pre-flash will then be far less obvious to the subject(s). You shouldn't really be firing it directly at your subjects anyway (without a diffuser) if you are aiming for high quality flash shots.

You could also try taking your own mugshot, (cable; remote; or just 2sec/12sec delay) and try and observe for yourself what might be happening.

I appreciate you may not want to risk total destruction of your gear, but in the name of research it's worth the risk.

Bernard

Indeeed - it's always driven me nuts. P-TTL is a complete PITA in that regard.

I've found that off-camera flash, especially if it's bounced, doesn't seem to make people so prone to blink. I guess cos it's not right in their eyes so much.

In any case, I get a lot less in the way of half-closed eyes with off-camera (even with all the pre-flash chitchat between the master and the slave(s)).