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11-30-2012, 01:35 AM   #1
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K-5 with old manual lens does not want to move the aperture

Hello everyone,
I have almost the same problem like LarsW in his post https://www.pentaxforums.com/forums/pentax-beginners-corner-q/186690-aperture...nual-lens.html, except my aperture won't stop down in any situation, it stays still wide open.

Until now I was using my K-5 just with AF lenses or M42 lenses and everithing was just fine. Yesterday i bought MC Petri 135mm f3.5 like this one Pentax K fit Petri 135mm 1:3.5 MC Telephoto Portrait lens | eBay . Lens apears to be in great condition with just few pieces of dust in it.
  • Focusing moves nice and smoothly
  • Aperture ring moves also pretty nice and the aperture is closing and opening respectively, when not on camera.
  • Aperture blades are dry and clean.
  • The stop-down lever moves with nature resistance and returns back in default position with the speed of light.
  • The "Using aperture ring" in camera menu is set to "Permitted"

Everithing seems to be set well, but the aperture stays still wide open and I don't have a clue why. I've tried Tv,Av,TAv, M modes .. still the same result. Please tell me, that I've just missed something and my camera isn't broken.

Thx, Kousalik

11-30-2012, 05:00 AM   #2
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dose this lens have "A" setting on aperture ring?
11-30-2012, 05:11 AM   #3
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No, it's full manual. Just aperture ring.
11-30-2012, 07:10 AM - 1 Like   #4
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The lever on its mount will set to the desired aperture once you press the shutter. Try to make two or three shots with different aperture, same speed and same ISOto check that its working.

11-30-2012, 07:20 AM   #5
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If it's a typical Pentax K mount, it should have an aperture arm on back, right beside the locking notch. If you hold it with the red dot on top it should be about 4:00 position. Look through the lens and push that arm, the aperture should open. If not, something inside is stuck and the camera is not able to stop it down when taking a picture. The camera holds that arm in the fiully open position so you can have enought light to focus, then stops it down to the aperture set on the ring when taking a picture. Sticky aperture blades can cause it to not close down properly. Watch it when looking through the lens, it should snap back to minimum aperture very quickly. If it moves slow, that's your problem.
11-30-2012, 07:39 AM   #6
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If it's a fully manual lens, you pretty much have to use it in M mode, using the green button for stop down metering. You can use Av, but it will only shoot wide-open. (assuming the lens is working properly)

Last edited by paulh; 11-30-2012 at 07:47 AM.
11-30-2012, 07:50 AM   #7
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If it is k mount, you have to use M mode to shoot, otherwise, it is pretty much wide-open metering. If it is m42 mount with A/M switch, then you can turn the switch to M for stop-down metering using the A shooting mode.
11-30-2012, 08:34 AM   #8
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Preview method should be set to "Optical" (Select "Button Customization" in the Rec. Mode 5 menu - Select "Preview Dial" - Select "Optical Preview")

In Manual metering mode the diaphragm should now close down when you operate the Preview Dial. This should also activate Stop-Down Metering and you can use the meter bar to set your exposure. This is really the only time the diaphragm will actuate on non-A K-mount lenses outside of releasing the shutter.

Also if you go into the E-Dial Programming you can set the Green Button for TAv & M to TV Shift. This allows the camera to set the shutter speed in Manual mode when you press the Green button.

11-30-2012, 08:40 AM   #9
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QuoteOriginally posted by soulman Quote
The lever on its mount will set to the desired aperture once you press the shutter. Try to make two or three shots with different aperture, same speed and same ISOto check that its working.
This would normally be the answer. To spell it out:

1)K- and M-lenses will work poperly only in M-mode.

2) The aperture will stay fully open until you actually press the shutter and take the picture or until you press the Green button or use the on-off lever for preview.

So, set you camera to M-mode, stop down you lens as much as you can and press the green button while you look through the vew finder. If the view dims momentarily while the camera measures the light, your lens and aperture coupling mechanism are both fine. If not, I would look for problems with the aperture coupling lever in the lens before anything else.
11-30-2012, 05:12 PM   #10
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Hi all, first off all, thank you for your responses!
I've read many articles about shooting with manual lenses and I'm using M42 lenses regurarly without problems in M mode. This one is original Pentax K-mount and I was trying to get it work in every possible mode. In most of the time in M mode. As I wrote in first post, aperture blades are moving without any sign of resistance, it moves like new lens when not on camera. I've tried many combinations of settings, many different exposure times, pushing the green button like thousandtimes on every aperture number, but nothing....still wide open. When it's on camera it just will not move. I'am starting to be afraid, that the problem is the mechanism in my camera :-(. It's like "there is the one last thing, I missed out to get it work". There is no sound, no sign of the camera trying to move with aperture. I think I'm just missing something obvious.

And by the way, sorry for my english. I hope, I'm expressing myself clearly.
Kousalik
11-30-2012, 07:28 PM   #11
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As I recall there was a post on the diaphragm control lever getting stuck on one of the K DSLR bodies and how to fix it. This could cause the some of the problems you are seeing. You can probably check this by dismounting the lens, turning on the camera and seeing how the lever moves on the camera when you actuate the Preview in Manual Mode.

Another possibility is the lens may have been disassembled and reassembled incorrectly so that the diaphragm control lever is out of alignment. Or it could just be bent. I had this happen to one of my Minolta MD lenses. You could open and close the iris off the camera by moving the lever but on the camera the lever was in the wrong position to actuate properly.

M42 lens use an entirely different system (not supported on K-mount bodies) for the auto-diaphragm. So if the problem is with the camera body it would not be apparent using screw-mount lenses.
11-30-2012, 07:42 PM   #12
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mount up a known good lens (one of your AF lenses is fine) and see if the depth-of-field preview function works while looking into the lens...
11-30-2012, 08:58 PM   #13
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The aperture won't stop down until you actually shoot or meter. Can't believe nobody has posted this link yet

https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html

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12-01-2012, 03:23 AM   #14
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gabriel_bc: when DOF previewing with my AF samsung, everything is ok, aperture is stoping down. When doing it without mounted lens, it makes some short creepy noise like "bzz" - same noise with manual lens and without this noise with AF lens, so it may be the clue.

Adam: as I posted before, it is not stoping down nor when mettering, nor when shooting. I've followed many similar "how to's", so I think everything is set well.

I can't see difference between stop-down levers on my AF lens and manual lens. They're both in same positions, moving smoothly and moving with aperture.
12-01-2012, 05:12 AM - 2 Likes   #15
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The lens also will not stop down if the camera doesn't detect that a lens is in place. If you try the "preview" lever without a lens in place nothing happens. The lens mount must be clean and conductive so that the electrical contacts can tell it is mounted. Some 3rd party lenses have anodized mounts that don't make electrical contact. Some people report "sandpapering" the back of the lens where it meets the electrical contacts to correct this problem, and others have tried a piece of foil over the contacts. Both methods report success - that the lens will then stop down.
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