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06-01-2016, 06:42 AM   #1
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Voigtlander Lens with a K Mount, not working correctly

I am trying to use a CV-125 APO with a Pentax K mount. I have other Voigtlander lenses (90mm APO [2 types], 40mm Ultron) in the Pentax mount, and they work fine. When I mount them, I turn the aperture dial to the narrow end, press a little tiny button, and move it to the "A" spot. At least this is what the Pentax folks call it. Once I have done that, I can change aperture and shutter. However, on this CV-125, I move it to the "A" spot, but nothing happens. Is continues to only show up as wide open. Any ideas please?

06-01-2016, 07:29 AM - 1 Like   #2
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I am unclear as to what you mean by "only show up as wide open". Are you saying that the viewfinder and other displays show "2.5" and that you are unable to change the setting? Or are you saying that the lens will not stop down regardless of what aperture you set from the body? Or are you saying that you are not able to set the aperture from the body. The last is the most common and what follows assumes that is your problem.

With the aperture ring in the "A" position the lens identifies itself to the camera that it accepts aperture control by the body. It does this through on of the contacts on the mount. If the aperture ring is not in the "A" position, "F---", rather than the aperture, is displayed on the top LCD, in the status display (rear LCD), and in live view. If "F---" is displayed, the lens will not stop down at exposure time or for DOF preview unless in M mode.

Rarely, "F---" will be displayed even with the aperture ring in the "A" position. Possible causes:
  • The contacts on the lens' mount face are not clean. These may be cleaned with a microfiber cloth.
  • The lens may be slightly out of align in the mount or is not fully engaged in the mount. Confirm that the lens is locked into the mount and wiggle it back and forward a few times to see if the the "F---" changes to a number.
  • The aperture ring may be a little "touchy" about that last position. Try moving it in/out of the locked state at the "A" position beyond the minimum aperture a few times.
  • There may be an internal fault in the lens such that on of the contacts (specifically the so-called "A" contact) does not signal properly to the camera
If you can't get the "F---" to go away, your immediate option is to shoot in M mode using the lens ring to set the aperture and the front e-dial or green button to set the shutter speed.


Steve

Last edited by stevebrot; 06-01-2016 at 08:29 AM.
06-01-2016, 09:47 AM   #3
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QuoteOriginally posted by stevebrot Quote

Rarely, "F---" will be displayed even with the aperture ring in the "A" position. Possible causes:

If you can't get the "F---" to go away, your immediate option is to shoot in M mode using the lens ring to set the aperture and the front e-dial or green button to set the shutter speed.


Steve
What you write is very clear. Thanks.

The lens (Voigtlander 125mm APO) as the "A" mark, but will not behave properly, no matter what I do. So, it is behaving like a lens with no connections, which I have as well.

The problems is that I need LiveView and it shows me only the lens wide-open, even if I turn the aperture ring on the lens itself to f/16. I need LiveView to reflect the aperture I set. Any thoughts?
06-01-2016, 10:37 AM   #4
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Interesting. I'll check mine when i get home tonight.

06-01-2016, 10:40 AM   #5
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QuoteOriginally posted by MichaelErlewine Quote
The lens (Voigtlander 125mm APO) as the "A" mark, but will not behave properly, no matter what I do. So, it is behaving like a lens with no connections, which I have as well.
That is not good but is probably fixable.

QuoteOriginally posted by MichaelErlewine Quote
The problems is that I need LiveView and it shows me only the lens wide-open, even if I turn the aperture ring on the lens itself to f/16. I need LiveView to reflect the aperture I set. Any thoughts?
From your comments on the other thread, think you mean that you want live view to provide some indication of DOF for the set aperture. For lenses having an "A" position on the aperture ring, you have two options.

Aperture ring on "A" position:
  • Manual focus
  • Live view
  • Set aperture on body. Mode should be B, M, X, Av, or TAv to allow this.
  • Use DOF preview (on/off switch far over) to stop lens down. You should be able to freely adjust focus.
  • Release the DOF preview to change to a different aperture. Aperture cannot be set from the body while DOF preview is active
  • The live view display will dim according to the set EV +/-.

Aperture ring off the "A" position (also Pentax-K and M series lenses):
  • Manual focus
  • Live view
  • Set aperture on lens
  • Use DOF preview to stop lens down. You may focus and change aperture at will using the lens rings.
  • The live view display will adjust to a uniform brightness even with the lens stopped down
It is not possible to have the lens stopped down full time with most K-mount lenses on any Pentax film or digital body. The exceptions are:
  • Full manual/fixed aperture (rare)
  • Pre-set aperture (rare)
  • When using bellows or extension tubes lacking coupling for aperture actuation
A short, extension tube with no aperture coupling or coupling defeated may be your best bet if you need fully manual aperture with your V/C lens. Something like the shortest tube (12mm) of this set might work for you:

http://www.bhphotovideo.com/c/product/896117-REG/Dot_Line_dl_mex_pk_Man_Ext_Tube_Set.html


Steve

Last edited by stevebrot; 06-01-2016 at 10:47 AM.
06-01-2016, 02:29 PM   #6
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Thanks Steve. Will try that in the morning. Good thoughts, well put.
06-02-2016, 08:09 PM   #7
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QuoteOriginally posted by MichaelErlewine Quote
I am trying to use a CV-125 APO with a Pentax K mount. I have other Voigtlander lenses (90mm APO [2 types], 40mm Ultron) in the Pentax mount, and they work fine. When I mount them, I turn the aperture dial to the narrow end, press a little tiny button, and move it to the "A" spot. At least this is what the Pentax folks call it. Once I have done that, I can change aperture and shutter. However, on this CV-125, I move it to the "A" spot, but nothing happens. Is continues to only show up as wide open. Any ideas please?
Hi,

I would check your copy if I were you - mine works fine. Maybe the contacts are dirty. I am using CV 125 and K-1. I can control aperture from the body, and live view works fine.
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