Originally posted by reivax 
I should mention that you do have to manually set the aperture using the aperture ring on the lens, but the camera does set the shutter speed for you once you've done this. Another thing to note is that the camera will not automatically compensate when using flash (or I haven't figured out how to do it) so all of the shots are extremely over exposed when using flash (I'm sure this can be corrected with manual flash settings, but I'm trying to point out the lack of automatic function).
Hi,
Here are the facts (and they apply to any DSLR Pentax).
With an M or K lens you need to use the ‘M‘ setting and the ‘green Button‘ to get a reading of the light. If you use the ‘Av‘ setting you will be shooting wide open, regardless of the aperture setting and you will get no reading of the light by pushing the ‘green button‘, except for wide open. Shoot.
With a M42 lens, with a manual/automatic switch, you can set the camera to Av. If you prefer a bright, wide open viewfinder, then you switch the lens to the ‘Automatic‘ setting and focus the image. Then you switch back to the manual setting to read the light, do your +/- adjustments etc. — and then you shoot.
With a M42 lens without a Manual/Automatic switch (you might need to modify the lenses ‘automatic‘ pin at the rear end first or only shoot wide open!), you can also set the camera to Av. You get the aperture that you set and thus a darkened viewfinder. The camera will make a reading of the available light — and you can shoot.
Kind regards
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