I have some Olypus lenses that were used with my OM20 camera that I would like to use on my Pentax K-r camera. Is this possible, and what would I need to do it?
A Google search for "pentax olympus adapter" turns up "Leitax", a provider of replacement mount that you have to screw onto the olympus lens.
You will also need to turn the Pentax camera into a mode where it works with the missing aperture lever that regular Pentax lens provide for measuring. This mode is called stop-down metering. You can read more about this on this pentaxforums page.