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06-23-2018, 12:05 PM   #1
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Aperture problem with manual lenses

Hello,

I have just got a K-3II and it's fantastic but I'm having a problem with my manual Pentax lenses which have aperture rings. I have tried a few lenses and I'm getting the same problem so I'm fairly certain there's nothing wrong with the lenses.

I can see the aperture blades opening and closing when the lens is off camera, but as soon as they get attached to the camera they open fully up and will not change despite what the aperture ring is set to.

My new 18-55mm WR kit lens works perfectly and after reading lots of reviews for my old manual lenses I thought they would work perfectly too.

Does anyone have experience of this problem? If so then is there a solution?

Thanks in advance!

Sam

06-23-2018, 12:13 PM   #2
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First "use aperture ring" must be enabled in the settings.

Then, lenses not set on "A" or without contacts will only stop down in Manual mode when the exposure is taken or the green button is pressed to stop-down meter or when the optical DOF preview is operated. With the K-3II in manual mode when you operate the optical DOF the iris will stop down to the setting on the aperture ring and the exposure bar can be used as meter readings - adjust shutter speed with the eDial and f-stop with the aperture ring.

All other modes except X and B will default to Av and meter and shoot wide open.

See these articles:
https://www.pentaxforums.com/forums/54-pentax-lens-articles/110657-how-use-m...-k-30-etc.html
https://www.pentaxforums.com/forums/53-pentax-dslr-camera-articles/100260-ma...ic-lenses.html
06-23-2018, 12:46 PM   #3
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QuoteOriginally posted by sjwomersley Quote
Hello,

I have just got a K-3II and it's fantastic but I'm having a problem with my manual Pentax lenses which have aperture rings. I have tried a few lenses and I'm getting the same problem so I'm fairly certain there's nothing wrong with the lenses.

I can see the aperture blades opening and closing when the lens is off camera, but as soon as they get attached to the camera they open fully up and will not change despite what the aperture ring is set to.

My new 18-55mm WR kit lens works perfectly and after reading lots of reviews for my old manual lenses I thought they would work perfectly too.

Does anyone have experience of this problem? If so then is there a solution?

Thanks in advance!

Sam
The aperture will only stop down to the value selected on the aperture ring when you go to take a photo. That's why you have to follow the procedure linked above to get a correct exposure.

Adam
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06-23-2018, 12:49 PM   #4
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QuoteOriginally posted by sjwomersley Quote
Does anyone have experience of this problem? If so then is there a solution?
Several people on this site in the last week or so, but usually not that many.

As noted above, the solution is to expect that your camera will work much like a fully manual film SLR when matched with any lens where the body cannot control the aperture*, but only if the menu setting is correct (menu --> C4 --> 24. Using Aperture Ring --> Enable) and only in modes without exposure automation (M, X, and B). Metering is always of the stop-down variety (as with the original Spotmatic film camera) and may be done using several different approaches, all of which do the same thing -- stop the lens down to allow either you or the camera to set an appropriate shutter speed.** Metering is limited to either center averaged or spot. There are special rules and approaches for M42 lenses due to the full-manual aperture of adapted lenses. Yes, the subject is broad (can take many words to explain), but how things are done are fairly simple.


Steve

* If the body is not able to detect the so-called "A" contacts on the mount and the "A" contact in particular, it will display F--- instead of aperture setting and will not be capable of exposure automation except at maximum aperture.

** The options, very quickly, are: green button stopdown and DOF (on/off/DOF switch) stopdown when using the optical viewfinder and green button stopdown in live view. The first two tend to have less reliable metering, while the third is essentially equivalent to green button + M mode with a lens having "A" contacts.

06-23-2018, 01:24 PM - 1 Like   #5
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Make sure you have the camera set to manual mode. In any semi-automatic mode full manual lenses will only be operated in Av-mode with full open aperture.

You can check the manual for more info on compatibility on old manual lenses.

Last edited by Fogel70; 06-23-2018 at 01:36 PM.
06-24-2018, 02:07 AM - 1 Like   #6
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Thanks everyone for your quick help!

I had the camera set to enable use of the aperture ring but I was in auto mode and just expected it to work. Tried it in manual and it's fine now! I've decided to programme the U1 and U2 profiles to be for specific manual lenses (Pentax-A F2.8 Macro 50mm and Tamron SP F3.5-4.2 35mm-210mm) I have so can just get on with using them next time.
06-24-2018, 04:55 AM   #7
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The Pentax-A should work in all modes as long as the ring is set to the "A" position. The limitations are manual focus (obviously) and only center focus point can be used.

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