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08-26-2016, 10:10 AM   #1
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Aperture ring not working when attached to the camera

Hi!
I have a Porst 1:4.5 75-260mm tele zoom working on my Pentax K-50.
I was taking some pictures today and I noticed that the only mode that it allows me to operate the camera is the Av - not even Manual mode I can use. It measures automaticaly the light and actually makes nice pictures, but always with the aperture ring set on 4.5. I tried many times to set it on the other stops, but the lens does not react.
Then I unmounted it, checked if the ring was working properly (it was), set on 22 and mounted back to the camera. The ring is automatically wide open again when attached and I don't know what to do.
I tried searching some informations about this problem, but it seems that almost nobody owns the same lens and couln't find any solution.

08-26-2016, 10:34 AM   #2
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All the info you need is found here:
https://www.pentaxforums.com/forums/54-pentax-lens-articles/110657-how-use-me...k-x-k-7-a.html

You should only use M mode.

Note that the aperture will only close when you actually take the photo or press the green button. This is normal.

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08-26-2016, 11:12 AM   #3
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QuoteOriginally posted by Adam Quote
All the info you need is found here:
https://www.pentaxforums.com/forums/54-pentax-lens-articles/110657-how-use-me...k-x-k-7-a.html

You should only use M mode.

Note that the aperture will only close when you actually take the photo or press the green button. This is normal.
Am I doing something wrong?
I have done all this settings before, but I still cannot make the camera working on Manual mode. Even when I select "M", it says Aperture Priority.
I just took some pics using 4.5 and 22. They have the same Shutter Speed (as the camera is aperating it automatically) and the same Aperture, although I changed it. The green button is not of any use.
08-26-2016, 11:12 AM   #4
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QuoteOriginally posted by felipeamaciel Quote
I noticed that the only mode that it allows me to operate the camera is the Av - not even Manual mode I can use.
Welcome to the Pentax Forums!

Set the camera to fixed ISO to allow M mode when using the lens aperture ring.

Auto-ISO and M mode on your camera is a strange mix, particularly when setting the aperture from the aperture ring. The strangeness goes like this:
  • When controlling the aperture from the body (most modern lenses), M mode with auto-ISO defaults over to TAv mode. This make sense from the functional perspective (TAv is functionally equivalent to M mode + auto-ISO).
  • When using the aperture ring, all automated modes (TAv included) default to Av with wide-open aperture only
  • Because of the point above, when auto-ISO is enabled,and a K-mount lens is mounted and the aperture ring is used, Av (lens wide open) is the only option*
Go figure...


Steve

* Things get interesting when fully manual aperture lenses (e.g. screw mount Takumars) are mounted. Behavior in that case is the same as Av + auto-ISO.

08-26-2016, 12:01 PM   #5
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QuoteOriginally posted by stevebrot Quote
Welcome to the Pentax Forums!

Set the camera to fixed ISO to allow M mode when using the lens aperture ring.

Auto-ISO and M mode on your camera is a strange mix, particularly when setting the aperture from the aperture ring. The strangeness goes like this:
  • When controlling the aperture from the body (most modern lenses), M mode with auto-ISO defaults over to TAv mode. This make sense from the functional perspective (TAv is functionally equivalent to M mode + auto-ISO).
  • When using the aperture ring, all automated modes (TAv included) default to Av with wide-open aperture only
  • Because of the point above, when auto-ISO is enabled,and a K-mount lens is mounted and the aperture ring is used, Av (lens wide open) is the only option*
Go figure...


Steve

* Things get interesting when fully manual aperture lenses (e.g. screw mount Takumars) are mounted. Behavior in that case is the same as Av + auto-ISO.
oh god, I could never expect that only this ISO setting would make such a difference! well, that's what I got for getting so used with my Super ME :P
Thanks, steve!
08-26-2016, 12:12 PM   #6
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Yup, that one gets a lot of people. Auto ISO can be enabled in M mode on select Pentax bodies, in which case you'll see TAv instead of M.

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08-29-2016, 09:31 AM   #7
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Auto ISO in M mode ..... It seems almost like a contradiction in terms! I'm assuming my K7 is not one of the cameras that has this, as I don't recall any option for it and certainly I've never noticed ISOs suddenly changing. When it is, as described by Steve there, functionally the same as TAv, it makes you wonder why it is there at all.... Just to confuse?
08-29-2016, 09:59 AM   #8
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QuoteOriginally posted by mcgregni Quote
Auto ISO in M mode ..... It seems almost like a contradiction in terms! I'm assuming my K7 is not one of the cameras that has this, as I don't recall any option for it and certainly I've never noticed ISOs suddenly changing. When it is, as described by Steve there, functionally the same as TAv, it makes you wonder why it is there at all.... Just to confuse?
The K-7 doesn't have it because it has the TAv mode dial setting.

Cameras without TAv on the mode dial (K-01) as well as entry-level cameras without a dedicated ISO button (all other PRIME M bodies) do allow auto ISO in M mode, which is how you access TAv on those cameras.

And yes, it's certainly confusing and really only justified on the K-01. I've seen some users go as far as thinking that their camera is broken because they couldn't get in M mode when the mode dial was set to M...


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