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03-31-2014, 08:33 AM   #1
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K-50 with SMC Pentax-M 50mm f/2.0

Greetings! I am a new owner of the K-50 and I have been trying to use an old Pentax-M 50mm f/2.0 lens with it. After having followed the necessary steps listed on the Pentax website for using old lenses with the K-50, I am still baffled about how to set aperture. When I mount the lens to the camera, the aperture blades are pulled wide open as the lens clicks into place and while the lens is mounted I am unable to change f-stops even though I am able to turn the aperture ring. What am I missing?

Thanks in advance for any help.

03-31-2014, 08:48 AM   #2
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It is held wide open until the picture is taken, this makes for easier focusing.

However it can't meter wide open, this is what the green button is for. It temporarily closes the aperture, meters the light and sets the shutter speed.

Make sure you're in M mode, in Av it will stay wide open when taking the shot.
03-31-2014, 09:06 AM   #3
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Apparently M-series lenses cannot be used with K-500, K-30, and K-50. Here is what Ricoh Imaging Support told me:

Using Older Lenses on a K-500, K-50, K-30
When using a lens without an "A" setting on the aperture ring (M-series, or screwmount with adapter), these (K-30, K-50 and K-500) cameras do not display the exposure scale in Manual exposure mode and the Green button cannot be configured to do a Tv shift. A-series or later lenses can be used in all exposure modes on the K-30, K-50 and K-500.

:/
03-31-2014, 09:23 AM   #4
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QuoteOriginally posted by oculus Quote
Apparently M-series lenses cannot be used with K-500, K-30, and K-50. Here is what Ricoh Imaging Support told me:

Using Older Lenses on a K-500, K-50, K-30
When using a lens without an "A" setting on the aperture ring (M-series, or screwmount with adapter), these (K-30, K-50 and K-500) cameras do not display the exposure scale in Manual exposure mode and the Green button cannot be configured to do a Tv shift. A-series or later lenses can be used in all exposure modes on the K-30, K-50 and K-500.

:/
Perhaps they should read their own support pages...

Using Older Lenses on the PENTAX K-50 | Ricoh Imaging Support

Make sure the camera is not set to AutoISO when you are in M mode. The camera has to be set to Manual ISO. The camera should turn off AutoISO in M mode automatically, like it does on every other Pentax that is not a K-01/K-30/K-50/K-500...

03-31-2014, 09:32 AM   #5
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Thank you, boris cleto! This was the answer. I was still in auto iso. Now everything is working smoothly. Many, many thanks.
03-31-2014, 09:32 AM   #6
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QuoteOriginally posted by oculus Quote
Apparently M-series lenses cannot be used with K-500, K-30, and K-50. Here is what Ricoh Imaging Support told me:

Using Older Lenses on a K-500, K-50, K-30
When using a lens without an "A" setting on the aperture ring (M-series, or screwmount with adapter), these (K-30, K-50 and K-500) cameras do not display the exposure scale in Manual exposure mode and the Green button cannot be configured to do a Tv shift. A-series or later lenses can be used in all exposure modes on the K-30, K-50 and K-500.

:/
...and your camera manual tells you something similar. That being that:
  • K-mount lenses without the "A" contacts offer a limited set of functionality on your camera
  • You cannot control the aperture from the camera body
  • You must use M mode only with no exposure automation features. This includes auto-iso* and other similar wizardry.
  • Stop-down metering is available using the green button
Translation? Your camera will behave in much the same way as the Pentax Spotmatic of 45 years ago.

That is not a bad thing. Think of it as the entry ticket into the realities of another age of photography.


Steve

* Too bad that Pentax did not continue the behavior of earlier models and have auto-iso disabled in M mode.

Last edited by stevebrot; 03-31-2014 at 09:39 AM.
03-31-2014, 09:35 AM   #7
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QuoteOriginally posted by stevebrot Quote
...and your camera manual tells you something similar. That being that:
  • K-mount lenses without the "A" contacts offer a limited set of functionality on your camera
  • You cannot control the aperture from the camera body
  • You must use M mode only with no exposure automation features. This includes auto-iso and other similar wizardry.
  • Stop-down metering is available using the green button
Translation? Your camera will behave in much the same way as the Pentax Spotmatic of 45 years ago and that is not a bad thing.


Steve
Thanks, Steve. The Auto-ISO was the issue. My 50 is nifty again.
03-31-2014, 09:42 AM   #8
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QuoteOriginally posted by oculus Quote
The Auto-ISO was the issue
Auto-ISO is evil, in my opinion.


Steve

03-31-2014, 10:51 AM   #9
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QuoteOriginally posted by oculus Quote
Apparently M-series lenses cannot be used with K-500, K-30, and K-50. Here is what Ricoh Imaging Support told me:

Using Older Lenses on a K-500, K-50, K-30
When using a lens without an "A" setting on the aperture ring (M-series, or screwmount with adapter), these (K-30, K-50 and K-500) cameras do not display the exposure scale in Manual exposure mode and the Green button cannot be configured to do a Tv shift. A-series or later lenses can be used in all exposure modes on the K-30, K-50 and K-500.

:/
I'm surprised nobody has linked to this article yet:
https://www.pentaxforums.com/forums/54-pentax-lens-articles/110657-how-use-me...k-x-k-7-a.html

Check out the text and the video. The steps to use manual lenses on your K-50 are the same as on the K-01 shown in the video.

Adam
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03-31-2014, 11:10 AM   #10
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QuoteOriginally posted by Adam Quote
The steps to use manual lenses on your K-50 are the same as on the K-01 shown in the video.
But despite the similarity of the processors,
the K-01 and K-50 are slightly different
since the K-01 only has one e-dial.
This makes the menu lines look different.
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