What can you guys tell me about this lens? I'm looking for a low light lens for my Pentax K110D. These seem to be fairly common on the used market for very reasonable prices. Lack of AF is not an issue, the "A" lenses feature open aperture metering, which would make them compatible with my camera's metering correct? Any other gotchas to look out for when using one of these (or any other older, MF lenses) on a newer digital body?