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06-21-2018, 11:22 AM   #1
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Pentax M 50mm f1.7

Hi, I just got this new lens and it is seems to be in perfect condition in every way. The problem is that when fully attached to a k-70 and k-50 it is not possible to stop down the aperture - rotating the ring has no effect, lens stays at max aperture.

Is this a common problem and is there an easy way to fix it?

Thanks
Tiago

06-21-2018, 11:35 AM - 1 Like   #2
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This will get you started
How to use/meter Manual & M42 Lenses on all Pentax DSLRs (K-1, K-3, K-5, K-30, etc) - PentaxForums.com
06-21-2018, 11:36 AM   #3
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The lens stays fully open until the photo is taken, then it closes down.
You can see the effect of stopping down if you program the Raw/Fx button for DoF preview.
Cheers
06-21-2018, 12:23 PM - 1 Like   #4
dms
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QuoteOriginally posted by bertwert Quote
The lens stays fully open until the photo is taken, then it closes down.
You can see the effect of stopping down if you program the Raw/Fx button for DoF preview.
Cheers
And you must be in M exposure mode for K mount lenses w/o an A setting (i.e., pre A/F/FA, etc. lenses)

06-21-2018, 12:26 PM - 1 Like   #5
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In short - put the camera in manual mode, select an aperture and press the green button. The camera will stop down the lens, take a meter reading and set the shutter speed. You can then override this speed if you want to. Compose, focus and press shutter button to take the picture, as per usual.

Great lens, by the way. I have one that I picked up for $20, attached to a broken Chinon camera. Some prefer it to the M 50mm f/1.4. I have one of those as well and I am still trying to make my mind up.
06-21-2018, 12:28 PM - 1 Like   #6
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K-mount lenses without "A" contacts only stop down in Manual Mode - when you press the green button for stop-down metering, take an exposure or operate the optical DOF preview. The lens will also stop-down in X or Bulb mode when you take an exposure or DOF preview. The green button does not work in X or Bulb mode.

See the thread linked above by paulh on how to meter using the green button in Manual mode as well as this one:
Manual Metering on Pentax DSLRs with Manual and Automatic Lenses - PentaxForums.com
06-21-2018, 12:40 PM - 2 Likes   #7
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The short answer is:
  • The aperture ring must be enabled in the custom menu settings. Doing so will allow the camera to stop the lens down for exposure, DOF preview, and stop-down metering.
  • Stopdown for is only possible in M, X, or B modes. Any of the auto-exposure modes will default to Av mode with the lens remaining wide-open at all times.

Steve
06-21-2018, 07:35 PM - 2 Likes   #8
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What stevebrot said. BTW, that lens is the greatest dollar-for-dollar value in the world. Yes, it is a bit soft at 1.7. Other than that, it is a winner. Sharp, almost zero distortion, decent bokeh, the clicks "feel" right, etc.

06-22-2018, 12:14 PM   #9
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Thank you all!


The slightly long process seems to be work but, in manual mode is there a quick way to set ISO?? Changing ISO in Manual mode on my K-70 is a pain especially because I use the pad for changing af points as default. Too many clicks, a serious interface issue, unless there is a workaround?
06-22-2018, 01:14 PM   #10
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QuoteOriginally posted by Tigs Quote
The slightly long process seems to be work but, in manual mode is there a quick way to set ISO?? Changing ISO in Manual mode on my K-70 is a pain especially because I use the pad for changing af points as default. Too many clicks, a serious interface issue, unless there is a workaround?
Why would you need AF points for a manual lens?


I change the ISO on my K-30 with the ISO button and the rear dial, the only way it could be simpler would be with a dedicated ISO dial.
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