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12-11-2015, 11:21 AM   #1
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Old K lenses on K50

After retiring and starting to run out of projects I decided I wanted to get back into taking some good photos. I broke out my old Sears KSX (Ricoh) film camera and four old K lenses. Early eighties. Did a search and discovered that most old K lenses could be used on the new Pentax DSLRs. After reading several posts and reviews on the subject I ordered a K50 body only.My question is in regards to the aperature operating lever on the back of the lens.I have two lenses that this lever locks or has limited travel depending on the aperture setting is this normal. I didnt want to damage the operator in the camera if this is a problem before using them. The lenses are Sears 50mm 1.1/7 and a Focal 28-80mm 1/3.5-4.5. The other two lenses that the lever operates freely and has full travel in all aperature settings are a Sears 80-200mm 1:4.0 and a Focal 28mm 1:2.8. I have read all the instructions and believe I have all the correct settings for the use of old k lenses. Do you think I can use these lenses without causing harm to the camera. I should mention that the first two lenses that have restricted operator movement do have full travel in the higher aperture settings (16). Thanks in advance for any advice. Ken

12-11-2015, 11:52 AM   #2
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Normal operation is that the aperture lever is held at the wide open position (lowest f number) by the camera. On pressing the shutter release, the aperture lever is released, and being spring loaded, will jump to the f-stop you have set on the aperture ring. Try it yourself. At each f stop the movement of the lever is restricted to that range.
This, I should specify, is in "M" mode on the dslr. If you try to use Av (aperture priority) the camera doesn't release the aperture lever, all your pics will be wide open aperture. This is because the KAF2 mount is missing the connection to the second mechanical aperture communication lever - the one in a slot opposite the sticking out lever. Av only* works if you have a PKA mount lens with an A position on the aperture ring. Now when you lock the aperture ring on such a lens on A, you should see that you can now see f-stop numbers displayed on the cameras lcd's, and aperture is adjusted using the speed dial on the camera. If your lens is set on A (or f22 with a PKM mount lens, no A) then you will be able to flick the aperture lever through the whole range of movement.

*there is a trick: only partially mounting the lens.
12-11-2015, 04:12 PM   #3
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QuoteOriginally posted by Mnwild Quote
I broke out my old Sears KSX (Ricoh) film camera and four old K lenses. Early eighties. Did a search and discovered that most old K lenses could be used on the new Pentax DSLRs.
One strong suggestion is that you check the lens mount for presence of the dreaded Ricoh "pin" before mounting other than a Pentax-brand K-mount lens to your K-50. During the 1980s, Ricoh sold a number of cameras that featured full program exposure automation using a Ricoh-specific variant of the K-mount. Those lenses feature a small spring-loaded pin or ball located at about the 7:00 position on the lens' mount face (when facing towards you). On some lenses, that pin/ball may intrude into the AF drive well on Pentax bodies and cause the lens to be "stuck" on the camera. Once stuck, the lens may be very difficult/impossible to remove without cutting something.

The pin is found on all Rikenon "P" lenses and on many third-party and store-brand (e.g. Sears) lenses dating from the mid-1980s. With third-party product, it is often in combination with a set of Pentax "A" contacts to allow compatibility of both Pentax and Ricoh cameras of the day.

Google "Ricoh pin" for images and articles describing the problem. There are also numerous threads and posts on this site. Note that the ball-type contact is far less likely to jam, though YYMV and caution is advised.

QuoteOriginally posted by marcusBMG Quote
Av only* works if you have a PKA mount lens with an A position on the aperture ring.
The rule goes like this...
  • Lens has "A" contacts ==> All exposure modes on your K-50 are supported with adequate support for PTTL flash
  • Auto-focus lens ==> All exposure modes + full PTTL support
  • No "A" contacts ==>
    • Must enable aperture ring in custom setup menu
    • Must be in M, X, or B mode for lens to stop down for exposure
    • All other modes will default to Av, but with no automated stop-down for exposure
In regards to the "partial mount" trick, there is a recent thread on the subject where the pros and cons and risks are fully explored.

https://www.pentaxforums.com/forums/58-troubleshooting-beginner-help/309332-q...n-m-trick.html


Steve
12-12-2015, 05:15 AM   #4
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Thanks for helping me understand the mechanics of the aperture lever and operator. I became concerned after reading about the warranty issues of the camera operator and the differences in the mechanical limitations of the operating lever on the 2 lenses. I was aware of the pin on the old Ricoh lenses and mine dont have those.

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