Originally posted by ricstew I have bought some Pentax extension tubes. They have the single contact for stop down metering.......which one day I will work out how to use
I'm not sure what you mean by "single contact for stop down metering." Stop down metering (required for pK-mount lens with no electrical contacts) does not require any contact. An extension tube that supports pK-A mount should have 6 or 7 contacts as in this photo:
From what I know, Pentax has never made any extension tube with pK-A mount.
For now, I assume your extension tubes have pK mount.
Originally posted by ricstew I have 2 A lens that I would like to use with them, 50mm 1.2 and a 35-105 ( 1/3.5 ). Now I have put them together and put the 50mm on but should I be able to focus with the focus ring? I can twirl that little ring both ways in and out and it seems to make diddly squat difference? Am I missing some thing? some thing very basic
An extension tube + lens combo does NOT focus to infinity. The point of using an extension tube is to focus at short (macro) distance. The lens's focus ring can be used, but it has very limited range. It's easier to focus by moving the whole camera setup back and forth.
Originally posted by ricstew Should I be using the A setting ( all I get is ---F ) or the aperture ring? I have the setting in the menu set cause I can use both lens without a hassle.
A pK-mount extension tube can be used only with lenses with aperture ring. In this case, the combo lens acts as a pK-mount lens. You have to use it in stop-down metering mode: set camera mode to M, use the lens's aperture ring to control the aperture, and use the green button or the AE-lock button (depending on the camera) to meter (note: if the camera is of K series, exposure will be off big time).
If you use a pK-mount extension tube with a lens without an aperture ring (or with a pK-A lens with the aperture ring set at A), there is no way to control the aperture. It's always at the smallest aperture.