Two questions about RB67 lenses

[xtolsniffer]

Hi all,
I have two quesions about RB lenses that I would appreciate some help with.
Firstly, does anyone know the bellows extension at which the exposure compensation changes on a 140mm Macro KL when using tubes? I have a very poor quality pdf and I can't read at which bellows extension the change from +1 to +1.5 with tube no.1 happens, +1.5 to +2 with tube no.2 and +2 to +2.5 happends with both tubes. Someone was kind enough to give the info for the RZ version of the lens, and I'm assuming it's the same optical formula so it should be the same factors?

Secondly, I picked up a very nice but very used 65mm Sekor C for a bargain price. Unfortunatly the ring in front of the floating element ring keeps rotating a little when I screw in a filter or take the hood off. I've found the screws to tighten it under the aperture ring (you have to remove the finger grips to get at two of them), but tightening them doesn't do the job completely, just helps a little, so I was wondering how to take the ring off totally and put some thread lock on it to stop it rotating. It's not a fatal flaw, just annoying and not worth the cost of a CLA. But if I undo the screws completely, they won't come through the holes on the aperture ring as they seem to big, and the front ring (with the filter thread on it) won't rotate more than a quarter turn before making a worrying grinding noise. Any advice?
BTW, this seems a common issue on this lens, I've seen a few on that big auction site that seem to have the same problem.

 

[epatsellis]

Check your PM's...


erie

 

[max_ebb]

Does the 65mm Sekor C have a floating element? I have one, and I thought that ring was just a depth of field scale.

 

[xtolsniffer]

It does indeed have a floating element, though I have tested the effect it has, and it is quite marginal, but it probably makes the difference between 'outstanding' and just 'superb'. The 65mm is my standard lens and it's a gem (aside from the minor problem with mine that is!)

 

[epatsellis]

The C does, the non C does not, and contrary to general folklore, the non C is quite a nice lens. This image was shot with one:

While the C version is sharper, with proper shading, and a more conservative DOF scale than on the lens, they can give quite satisfactory performance, especially at the prices they're selling for these days.

erie

 

[max_ebb]

Wow, good to know. I recently bought a 65mm C lens to use on my RZ (wide angle Z lenses are outrageously expensive). I've only used it once so far, and I have no idea where the floating element was set (the resulting images were great though). I'll have to remember to set the floating element whenever I use that lens.