Mine makes a very quiet, as you say, scratchy hum, when the shutter's open, with or without SR.

"loud scraping / buzzing noises" don't sound good, though.

Is it possible that the AF screw slot is worn, and didn't engage properly? Just clutching at straws.

Something with legs, moving. Very dark on my monitor.

Could it be a spider?

If you're going to buy it, start working out now.

I have the A version (McBrian's before me), and it's fab. But assuming it's the same size, it's a beast compared with the much smaller and lighter Sigma 400mm F5.6

To give you an idea, here are both of them (note, both hoods closed):

The Pentax Remote Control F?

It does work with B exposures (on the K10D at least). You just hold the button down for as long as you want the shutter open.

And, incidentally, don't pay any attention to the Pentax claim that the battery in the Remote Control F is not replaceable. Undo the tiny screws, take it apart carefully, and you'll find a standard size watch-type battery that can be replaced easily.

If you do find a cheaper generic one, ensure that it'll allow you to do Bulb exposures by holding the button down. The Pentax one does.

Incidentally, from Matt's reference:

"Today most manufacturers use a series of high frequent flash bursts (say 50 kHz) with reduced single light emission to simulate a (theoretically) long single constant flash burst."

50kHz for 1/180s is 277 flashes

If correct, it explains why the timing doesn't have to be precise at all, since each part of the frame gets exposed more than 10 times at 1/4000s.

I never doubted it

I didn't just mean you, trust me..

It's remarkable that it's so easy to forget that a 'shutter speed' 1/4000s is really nothing of the kind. Each part of the frame may only see light for that length of time, but of course the whole exposure presumably takes much the same time as the sync speed.

I wrote this:

and subsequently this:

As you say, it does seem amazing. I'd be interested to know where my assumptions or calculations are wrong.

No disagreement there!

By the way, did you notice/agree with my fag-packet sums about HSS flashing?

Does it really flash 20-odd times as the curtain-gap crosses the sensor?

Well I take your points. But I still think it's very weaselly of them not to update the manuals properly, or at least put unequivocal addenda on their web site.

The K10D manual says "Wireless mode is not available with the built-in flash". But as we know, firmware 1.1 added this feature.

All they said was, "Using the camera's built-in flash, you can now wirelessly control external Pentax flashes. Previously, you needed an accessory flash mounted in your camera's hot shoe, but now the built-in flash can act as a control flash."

Personally, I think if they're going to say "beforehand you couldn't use wireless but now you can", then it's not an unreasonable assumption to that the features described in the flashgun manual will work - otherwise, how are we expected to know how to use them?

But what they actually mean, but failed to say, is "but actually we haven't implemented all the features you'll find described in the flashgun manual, and we aren't going to tell you which we have and which we haven't."

I think this counts as bad communication.

There's nothing much wrong with the Samsung book per se. They've cut a few bits out that refer to the Pentax cameras, which is a shame, but otherwise it's virtually a word for word copy of the AF540FGZ manual.

So did wireless HSS work with the MZ-S?