[jeffkrol]

Seems there is a solution to the fact that you can't shut dark frame noise reduction off in the k20 Bulb mode.
Re: K20d bulb problem: Pentax SLR Talk Forum: Digital Photography Review
found a way how to shoot lightnings!

Put to *M*
- F8 (depends on weather conditions)
- Shutter - 4s
- and wireless shutter locked like in bulb mode.
And K20d is taking pictures one after another without that feeling to have NR.
I forgot to write that you must set it to "continuous shooting".
For longer exposures:
4 seconds - no noise reduction (camera saves image right after closing shutter)
6 seconds - no noise reduction
8 seconds - no noise reduction
10 seconds - noise reduction ON (it needs about 7s to edit and save image to card)
So all above 8 seconds is useless.
I think this is only way to shoot lightnings and not to miss it
Regards,
D.
Seems like it would introduce some mirror shake though.

[vizjerei]

really take them a long time to write a hot fix in a firmware to fix that eh?..

[LeoTaylor]

really take them a long time to write a hot fix in a firmware to fix that eh?..

If you are waiting for a firmware fix remember us K100D owners have waited years for Pentax to provide a Remote Assistant for our cameras. I've given up checking the web site to see if they announced something between version 1 (istD) and version 3 (K10D and up). There must be some reason they can't get R.A. to work reliably with K100Ds. I suppose I should give up complaining about it, they don't seem to be listening.

An otherwise happy owner.

[lock2nl]

Well, it looks like it works indeed. Ari from Finland checked it, and as I suggested, he even combined it with the multi exposure- option. This effectively lengthens the total exposure time to as high as about 72 seconds in stead of the 8 seconds limit.
Unfortunately, I have not been able to check it myself cause I already returned my k20d after having tested it for a week. This very thing, the forced NR, was one of the reasons I was not going to purchase it.

lock

[falconeye]

Put to *M*
- and wireless shutter locked like in bulb mode.

This explaination was also added at dpr:

I used shutter pressed all the time.
It's like in bulb mode, when you "lock" shutter and it's alweys pressed.
You must set time for few seconds and not to use bulb mode.

With the Multi Exposure comment above. Maybe, it even works in Av mode and +2EV exposure compensation to get at 32s?