Originally posted by rosettaquarrier I do wonder what this round translucent plastic piece is that came in a Pentax pouch? Anyone have any ideas?
I remember getting one of those with some of my Pentax film camera bodies. I think I may have one or two still around. The spacer is, as several have indicated, a "tripod spacer." Although the majority of pan-tilt heads have a locking ring so the mounting screw does not have to be twisted deep into a camera body, ball heads must be threaded in until they are tight, and their mounting thread might be too long. I remember distinctly reading the instruction manual (back then you could actually read through once and remember everything about the camera operation) that specifically described the spacer as a way to deal with over-long tripod head mounting screws, not oversize lenses. There was even a diagram to show the problem, with a permissible maximum length for a tripod-head mounting screw. I have one old manual that might have such a diagram. I'll check on it.
NO! My memory was not correct. I'm allowed at my age.
OK, just did some searching and I was in error. The LX manual specifically states that the spacer is intended for use with lenses that have a large diameter where they fit against the front of the camera body, such that the rearmost part of the lens extends below the base plate. Chances are the Pentax people had certain specific existing Pentax lenses in mind that did not have a tripod foot and when mounted on an LX extended slightly below the base plate right at the front of the camera body.
I did some more checking and looked up the manual for an ME Super, which was my first K-mount Pentax and like the LX came with one of those white spacer rings. On the page for mounting on a tripod, the instructions first warn not to use a tripod head with a mounting screw longer than 5.5mm (0.22 inches) as that was the maximum depth of the tripod socket on the camera. Immediately after it advises using the spacer for lenses of large diameter. So the problem of a Pentax lens with a rear section that could extend below the level of the camera's base plate goes back at least as early as the ME camera body. Again, there must be some specific Pentax manual focus lenses that had this problem with the very compact Pentax Film Era cameras. Perhaps it was some of the near-normal FL lenses with a very large aperture such as a 50mm f1.2, or perhaps it was specifically the 28mm shift lens, perhaps both.