K100D optical preview

Just had my K100D a week and delighted with it, however I can't seem to get either the optical or digital preview to function. The book said you can select either, which I did from the menu, opting for optical preview, but when I rotate the shutter release collar having half pressed to focus, the optical preview and hence depth of field seems not to work (and I am selecting an aperture which is not wide open). I'm keen to use this plus I believe I need to use this to meter if I use older lenses which are not DA or A. Not fussed about digital preview but would like the optical option to work
Is my new baby faulty - or am I doing something wrong here?
Thanks folks

To get DoF Preview working all the time: In the Custom menu, set "Using Aperture ring" to "Permitted".

However, you don't have to use the The DoF Preview to use a non-A lens. In Manual mode, press AE-L to get a meter reading and set the shutter speed. You are free to vary the setting from there manually if you want some compensation.

Av mode is useable as well when the lens is wide open.

Pete
Thanks for the quick reply, however I'd already had that option set to allow the aperture ring to be used and I still don't seem to be able to get the optical preview (or digital for that matter) to work.

But yes, you are correct in that I don't actually need to operate it to meter with a older lens (depoite what the manual says!) So metering with my collection of older lenses is possible - but still no depth of field check with these or any other lenses at the moment.

On my K10d, the appature will not be stopped down on older lens set to the appature unless I am in Manual mode.

I would lets the function first with the digital priview option.

If the lens is set to 'A' then it should work - use apature priority mode to check.

Using ANY and ALL lenses set to a manual F stop (not 'A') on Pentax DSLR's imposes restrictions (This includes A, F, and FA series lenses and applies equally to older lenses having no 'A' setting). This does not apply to FAJ or DA series lenses because they have no aperture ring.

You can only use stopped down metering and DOF preview in M (manual), B (Bulb), and X (flash synch mode on K10D) modes.

In addition, you must set the relevant custom menu option for your camera model to allow use of the aperture ring.

Ok folks, thanks for that. As I was beginning to suspect, I have set the camera correctly - apperture permitted, Manual setting, Manual focus and still the optical preview does not work, although the meter does function correctly with the AE switch activated. So I guess there must be a fault with my new K100D. The digital preview also doesn't function, so I think the issue is probably with the ON/OFF/PREVIEW switch............So I guess my new camera will have to go back or I live without DoF preview :- (

I wouldn't live with it if it's faulty after such a short time. Take it back to the shop and don't leave until it has been replaced.

I would also take the lens and test the function in the shop!

With a KA-mount or autofocus lens, do you get the mechanical sound when you rotate the collar, or just nothing? It should work in all modes, and stop the lens down to the aperture selected in-camera.

Also, in Manual mode with a K-mount (M) lens, or any lens not set to auto aperture, the AE-L button stops the lens down, meters, and releases it again. That's the only way it can meter - so, when you say that it meters correctly, does it stop the lens down briefly then?