silk tree w/50mm
For zooms, I found a 28-100 f/4P early on, but it had some issues that super-glue resolved. It also seems to have optical issues, its contrast is mighty poor - plus at 600g it's just not going to get out much. In seeking a replacement I've won bids on two other Rikonon-P zooms, the 35-135 and 28-80 f/3.5-5.6. When they arrive I'll update this page, pick out a winner and let the others go, and maybe seek another Rikonon to dethrone it.
In my searching for lens information, I found a great site for Rikenon data - check it out here. I wish I had found this page earlier, as it shows the 35-135 weighs 500g, still a lot but perhaps it will do. Both the lenses I ordered have 58mm filter threads, so my current polarizer will work with them, saving both expense and hassle. I knew the 35-200 and 60-300 weighed a lot, so I've resisted those two.
Ricoh has been in the camera business for a long time, and they used both M42 and PK mounts in parallel with Pentax. In several cases I've heard claims that early Pentax and Ricoh lenses are identical other than the SMC optical coating; I cannot verify that and feel no need to research it.
One item that's noteworthy is that some Ricoh lenses have a strongly-projecting pin on the mount that needs to be removed, otherwise it pops into Pentax' AF screw-drive slot and the lens gets stuck! Some lenses have just a gentle, rounded button that slides past the drive slot, but others will be nearly impossible to get off the camera if the pin stays on the mount - so be careful! Also note that Ricoh seems to have been a source for Sears, Montgomery Ward and other 3rd-party vendors, so look carefully. A contact pin/button on the auto-aperture lenses is expected, but a separate pin should be matched up to the mount to see where it will fall, and removed if it's not intended to touch the Pentax body's contacts. Just remove the bolts on the PK mount and invert; it seems a couple of tiny screws hold the pin down, so unscrew one, twist the retaining bracket aside and push the pin out through the back - or just remove both bracket and pin. This is what I've encountered on a single lens, so I cannot claim they all look like this..
I'm looking forward to trying out these lenses against the 28-100. I also have a Promaster 28-70 that is functional and lightweight (and is a true A-type mount!), but has a lot of play in zoom and focus. I'll see how they fare soon, and I'll let you know! As with all tests, these are single copies from which I shall make wild claims; your copies will not likely do what mine do, nor is what I shoot a match for your interests - so let's not get carried away on this. My tests will be casual in any case, seeking sharpness bokeh flare and ease of use - and little else.