HS flash in Tv with K10D and AF360

I have a K10D (firmware 1.30) and AF360 flash.
The manuals seem to imply the High Speed (HS) flash sync will work in Tv and M modes.
With the flash on the camera and set to HS:
-In manual I can set successfully set exposures shorter than the sync 1/180, and the picture come out as expected.
-However in Tv the shutter speed dial will not let me set a speed shorter than 1/180
I would be grateful if someone could point out what I am doing wrong, or if the manuals are not correct, or if I should get my camera checked out.
Thanks Rob

I think you'll find that high speed synch refers to shutter speed, and it only works with shutter speeds faster than 1/180th.

When using shutter speeds up to 1/180th the shutter curtains are fully open (the sensor/film is entirely exposed) at the time the flash is discharged. Faster than that, and the trailing curtain starts to move before the leading curtain has reached the end of its travel. This means that the sensor/film is never fully visible therefore the flash has to fire a number of pulses to expose the entire sensor/film area.

I've never used HS Synch personally and if my perception of its operation is incorrect, Matt'll put it straight.

I think your camera/flash is operating correctly.

Peter we have moved to digital now, no curtains in the K10D you know

Rob, I will check it out tomorrow with the K10D and the AF540.
I mostly use full manual controll when using flash so don't know precisely but will give you the results of my findings tomorrow.

The magic latern guide says also that it works in Tv and M mode.

Oh yes there are Stefan. Well, they might be metal, rather than cloth, but they are still there and still called curtains as far as I know.

Take your lens off, set 2 second timer (mirror lockup) and look into the camera whilst taking a pic. You'll see the familiar shutter curtains.

Hi All
Thanks for your thoughts so far.
I think I have the answer-it would appear to be a bug somewhere in the firmware. With HS on the AF360, on the camera if ISO is set to Auto then in Tv the shutter speed cannot be set higher than 1/180, but switch to manual ISO and all higher speeds can then be used.
Cheers Rob

Yes Peter, you are right, sorry for the mistake.
I only wonder why they are still there, they aren't needed so far as I know since you can simply cut off the sensor when the time is over. The Panasonic G1 works without one for sure. Does the K20D also still has them?

Glad you found the problem Rob, you hardly ever need HS mode mostly only on sunny days and you want to use the flash. The UK can't be called a sunny place I believe

Point 'n shoot cameras use an electronic shutter (no moving parts) which is why so many of them use 'live view' in preference to a proper viewfinder. Some have both of course.

As far as I know the K20D has a real shutter and I'm guessing that it's required to achieve the very fast shutter speeds available on SLR's

The Panasonic G1, which is close to a DSLR can do 60 - 1/4000 seconds so don't think that's an excuse to use them.
Also mechnical parts are slower then simply stopping the electronic signal.

The only thing I can think of is because it's there to protect the sensor, might be handy to keep the dust and such out.

Rob,
You may find it easier if you map the ISO to one of the wheels in Tv mode (and Av mode). This enables instant access to the ISO. Pressing the Green button puts it into Auto ISO and adjusting the wheel puts straight into manual ISO
(Alternatively you can access ISO directly by holding down the OK button and moving the front edial. Again, holding down OK and pressing the green button will engage Auto ISO).
HTH!

Stefan,
Going slightly OT...
It depends on what type of sensor is being used as to whether a shutter (yes, with curtains) is needed. The sensors used in dSLRs (like the K10D, and most other makes too) need a physical shutter.

IIRC, they differ in the way the pixel values are read out. The dSLR reads out a column (or row) at a time, and because of this time lag needs a physical shutter. The compact digicam electronics can "freeze" the image and read it out when needed - and therefore do not need a physical shutter (it's done in electronics instead).

Wish I could find the web page describing it...
Matt

Matt, I will take your word for it.

Looked a bit for myself and found this.
- mirrors on all SLR and DSLR cameas are semi-transparent. If you lift the
mirror slowly up, you'll see another smaller mirror underneath, at 45
degrees, and AF and exposure sensors below, where these are located ever
since invention of SLR system.

- the fact that mirror is semi-transparent has nothing to do with live
preview - shutter curtain is still closed until you press the button.

- DSLRs have short lag because of the fact that CCD and CMOS (respectively)
are precharged and ready to capture.

- most consumer cameras have no mechanical shutter to speak of, they use
aperture iris for that function. That's why there is a big lag. When you are
looking at live preview, CCD is constantly refreshed, and iris open all the
time. When you press the shutter, iris closes COMPLETELY for a split second
to allow CCD to pre-charge, only after that iris opens to pre-measured
value, and image is captured. There is none of that process in DSLR, all
measurement regarding AF and exposure is done by external devices.

That seems to account for the annoying delay which occurs with some P&S cameras which means they fire somewhat after the thing you wanted to take a photograph has happened. I took my first digital camera to Switzerland and kept trying to take pictures out of the window of various trams, trains, cog railways and cable cars only to get a blurred picture of trees because the f... thing wouldn't fire.