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04-13-2014, 12:14 AM   #1
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Rikenon 50 mm f 1.4 A setting issue

I have just received this lens, and have made several test shots with K-7 and K-5II. Overall, it is a well-built lens with tons of sharpness and beautiful out-of-focus background. I expect to use it for portraiture, along with the 77 limited.

This is the Rikenon-P (Ricoh) lens, which I take to be equivalent to the Pentax-A lenses. However, the Rikenon-P function does not work on my cameras. The lens only functions as an M-type lens. I am still happy to have it since M type usage will be my primary application. However, I will appreciate any comments on this lens and why the P function is not working.

04-13-2014, 12:37 AM   #2
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The Ricoh P and Pentax A were different. That is what the Ricoh pin is for, it has no use on Pentax.

Some third party lenses have both the Ricoh pin and the Pentax A contacts, but I don't believe any Rikenons do.
04-13-2014, 01:39 PM   #3
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QuoteOriginally posted by ivanvernon Quote
This is the Rikenon-P (Ricoh) lens, which I take to be equivalent to the Pentax-A lenses.
Unfortunately, they are not the same. They were competing systems to allow programmed auto-exposure at the time they were made. A close look at the mount will reveal that there are no contacts that match those on your camera. There is just a single pin (the infamous "Ricoh Pin") or ball-type contact. Yours is probably the ball-type.

The Ricoh P variant of the K-mount has been a long-standing problem for Pentax AF camera owners. For some reason Pentax engineers placed the AF drive of their cameras at the same location as a protruding pin present on a common type of K-mount lenses (those supporting the Ricoh P mount). The pin may extend into the AF drive well on lens mount resulting in the lens being "stuck" on the camera. This is a dire situation when it happens because the lens be almost impossible to remove.

Therefore it is always a good idea before mounting a vintage non-Pentax K-mount lens to take a careful look-see to ensure compatibility:
  • Does the lens say K/R, K-R, or Ricoh anywhere on the barrel or mount?
  • Does the lens have "P" on the aperture ring?
  • Look for any spring-loaded pin or protuberance in the region of the AF well?
To make matters even more complicated, there are to versions of the Ricoh Pin. The first is an actual spring-loaded pin that protrudes when the aperture ring is off the "P" setting. That is the deadly kind. The other variety is a spring-loaded ball or round-headed pin that is less likely to fall into the AF drive well and cause grief.

As noted above, some 3rd-party lenses supported both systems and have both "A" contacts and the Ricoh pin. Those usually have an "R" somewhere on the mount or barrel and seldom have an "A" on the aperture ring. "P" or "Auto" or "AE" may be used instead.

Since you have not had any problems with your Rikenon-P, it is probably safe to assume that you have the benign form of the pin. Whew! As such your lens will work quite nicely though as a non-A K-mount lens on your camera using M mode and green button (stop-down) metering.

One final note for completeness: Most Rikenon lenses are perfectly safe and compatible on Pentax AF cameras. It is only the Rikenon-P models that have the potential to cause problems. XR Rikenon, Auto-Rikenon, and just plain Rikenon are perfectly safe.


Last edited by stevebrot; 04-13-2014 at 01:48 PM.

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