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07-07-2013, 03:43 PM   #1
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Super Tak Metering Problem

I've been shooting with my Super Takumar 55/2 as my single in July. First time using an M42 on my K-30, but used them quite a bit on my KX (The Tak and a Helios).

When I place my K-30 in M, the green button metering seems to default to whatever the sunny 16 shutter speed would be. The button is set on Tv Shift, and it does change the shutter speed, but no matter where I set my aperture on the lens, and no matter what the light, the shutter speed chosen is the inverse of the ISO setting (i.e. the correct shutter speed for sunny 16). If I go to Live View, the green button meters correctly and chooses the correct shutter speed. If I put an M lens on, it likewise meters correctly. If I switch to Av mode, it constantly meters (correctly).

I'm pretty sure I used the green button to meter on my KX with success, and I recall that it was a more reliable way to control my metering process, since I could use it to lock exposure on a specific point. It's possible, and perhaps more likely, that I'm crazy and it never worked that way, but man, I really think it did.

Is there a menu setting I missed somewhere?

07-07-2013, 05:26 PM   #2
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Didn't this identical question come up just a couple days ago? For your K-30:
  • Aperture ring enabled
  • Lens A/M switch on M position with the lens set at the desired taking aperture
  • Camera in M mode
  • Green button setup to do stop-down metering using P(rogram) line. (I don't think that Tv shift is going to do the job here.)
When you push the green button the shutter speed should change to what is appropriate with the lens stopped down. It should stay at that speed until you change it manually (this is M mode after all) or push the green button again under different lighting.


Steve

Last edited by stevebrot; 07-07-2013 at 05:33 PM.
07-07-2013, 08:26 PM   #3
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Aperture ring enabled, lens set correctly, camera in M mode. My problems is that no matter what the aperture is set to, no matter what the light level is, the green button changes the shutter speed to a bit past 1/ISO. So if I set ISO at 200, I get 1/500 shutter speed. ISO 100, I get 1/250. Aperture doesn't matter. Inside, outside, point at the sun, point at a black hole. No difference.

Also doesn't matter if I set the green button to PLine or TvShift. Same behavior. Works fine with an M lens, only the M42 is acting stupid.
07-07-2013, 08:39 PM   #4
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QuoteOriginally posted by Kozlok Quote
Also doesn't matter if I set the green button to PLine or TvShift. Same behavior. Works fine with an M lens, only the M42 is acting stupid.
I'm still learning myself using manual lenses on digital cameras, but it should not make any difference what manual lens you are using, should it?

I mean, the camera has no clue if there is an M, A or M42 lens mounted, right? You set the camera to enable the aperture ring so it prompts you for focal length when you turn it on, then proceed to take pictures in manual mode.

I still haven't bothered with using the green button as you describe. I just select the correct or nearest focal length, compose the shot, meter for the light at the chosen aperture and select the correct shutter speed and press the shutter button.

Then I review the shot (how did we ever get by in the film days without this instant confirmation of our settings?), make adjustments and shoot again if needed or move on.

07-09-2013, 06:55 PM   #5
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Anyone have an idea if my K30 is just not working right? Is there some secret hidden setting somewhere?

I know for sure green button metering worked on my KX, but damned if I know why it won't on my K30?
07-09-2013, 07:10 PM   #6
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What adapter are you using? Are you toggling the auto/manual switch on the lens to manual so that the aperture actually stops down. If left on auto the aperture stays wide open no matter what you set the ring to. Your lens also has to be screwed in far enough so that the auto/manual lock release is depressed. Otherwise the switch will lock and you can't change it. Some third party adapters might not depress the lock release.

Using K-30 With Older Lenses | Pentax Support

To set up your PENTAX K-30 to use older PENTAX lenses:

Press the Menu button

Using the buttons on the four-way controller on the back of the camera, navigate to the [C Custom Setting 4] menu.
Navigate to [23 Using Aperture Ring] and select [Enable]. Press the OK button and then the Menu button to exit.

20120810-114611.JPG20120810-114626.JPG20120810-114631.JPG

(This setting allows the camera to operate with older PENTAX lenses which do not have an aperture controlled by the camera body such as PENTAX K-series and M-series lenses).

Press the Menu button

Using the buttons on the four-way controller on the back of the camera, navigate to the [Rec. Mode 4] menu, select [E-Dial Programming]. Press the right button twice on the four-way controller.

20120810-114646.JPG20120810-114658.JPG20120810-114729.JPG

Press the down button to highlight the line beginning with “M” and press the right button on the four-way controller. Highlight [P Line] and press the right button on the four-way controller. Highlight [Tv Shift] and press the OK button. Press the Menu button three times to exit the menu.

(This setting allows easy and accurate exposure metering using older lenses without an "A" setting on the aperture ring. When the Green button is pressed in Manual exposure mode, the lens "stops down", the camera's meter measures the light passing through the lens, and an appropriate shutter speed is automatically set based on that measurement).

Note: when using lenses without an "A" setting on the aperture ring, Manual exposure mode must be used. Exposure can be set by adjusting the lens aperture ring and/or adjusting the shutter speed on the camera.

Note: If Shake Reduction is enabled when using an older lens, you will need to manually select the closest matching focal length from the Input Focal Length menu. To do this:
Turn the camera off. Mount the non-"A" series lens. Turn the camera on.

The Input Focal Length screen will appear. Use the rear e-dial to select a focal length which is closest to the focal length of the lens you are using. If you are using a zoom lens, choose a focal length close to the midpoint of the zoom range of the camera. Press the OK button when you have made a selection.
07-09-2013, 07:59 PM   #7
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A/M switch on the lens is correct. I know for sure that the aperture is working. I used M42's for many many shots on my KX. I'm pretty comfortable with it.

Camera is set correctly for Aperture Ring Enabled and Tv Shift, using M. ISO is set to manual.

The thing is, after pressing the green button, I get the same shutter speed if I point it at the sun, or put the lens cap on, so the camera isn't metering at all. It's just giving me a shutter speed larger than 1/ISO (at ISO 200 I get 1/250, ISO 400 gives 1/500, etc).

Also, If I set green button to Pline or Disable, it still gives me Tv shift to the same fixed value.
07-09-2013, 08:14 PM   #8
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UPDATE. If I switch to live view and press the green button, the camera meters correctly. If I then switch live view off, then the green button will shift the shutter speed based off of this value if I change ISO. Say the Live View meters to 1/20 at ISO 100 in Live View. Switch Live View off, press green button, shutter speed stays near 1/20 regardless of aperture and actual light levels. Change ISO to 200, shutter speed goes to 1/40, ISO 400 give 1/80, etc. Turn camera off, back on, press green button, back to 1/125 at ISO 100, 1/250 at ISO 200, etc. I think the green button is not metering at all in normal operation, but is working fine in Live View. I'm thinking something is wrong with my camera?

Also tried a different M42 lens (Helios), same behavior.

07-09-2013, 08:32 PM   #9
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You said that green button metering works fine in M mode with your M-series lens, but not with your adapted M42 lenses. I am with Racer X...The camera has no way of knowing that the difference between a M-series and adapted M42 lens.

You also said that you get "sunny 16" settings regardless of amount of light hitting the sensor. What happens if you meter in a dim room with no lens on the camera?

Might you try resetting the camera to factory settings and start over with the only change from factory being to enable aperture ring?

If the camera is still on warranty, you might try Pentax telephone support.


Steve
07-09-2013, 10:14 PM   #10
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Lets go back a step. You said it meters correctly in Av mode? Or was that your Mseries lens?

The real interest for many people using M42 lenses is to work in Av mode. Working in M mode with M42 lenses should be the same, but with metering active only when you press the button, assuming it is not reprogrammed some how
07-10-2013, 07:41 AM   #11
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An M camera touches the contacts. Pressing the green button activates the aperture lever. With an M42 lens, the contacts are not shorted, so the camera does know the difference.

Yes, metering to with the m42 lens works fine in Av mode. Green button metering does not work, and my personal experience is that green button metering, at least on my kx, was more reliable.

I may try a factory reset.
07-10-2013, 09:42 AM   #12
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QuoteOriginally posted by Kozlok Quote
An M camera touches the contacts. Pressing the green button activates the aperture lever. With an M42 lens, the contacts are not shorted, so the camera does know the difference.
Ummmm...pressing the green button ALWAYS activates the aperture lever. At least, it is supposed to. Whether contacts are shorted or not should not make a difference since there is a wide variety of conductive vs. non-conductive M42 and K-mount flanges. I have examples of both K-mount and M42 lenses on my shelf with both conductive and non-conductive bases.


Steve
07-10-2013, 01:52 PM   #13
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QuoteOriginally posted by stevebrot Quote
ALWAYS activates the aperture lever. At least, it is supposed to. Whether contacts are shorted or not should not make a difference since there is a wide variety of conductive vs. non-conductive M42 and K-mount flanges. I have examples of both K-mount and M42 lenses on my shelf with both conductive and non-conductive bas
I don't think that's true. Wasn't true on my KX, and definitely not true on my K30 Take the lens off, hit the green button, no motion of the aperture lever, I'm sure.
07-15-2013, 02:37 PM   #14
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My experience with my k-r is the same as Kozlok. Painted flanges on most M42 lenses mean no electrical connection and green button DOESN'T work (with any of my half dozen M42's).
I use A mode but then the issue becomes bizarrely large exposure compensation (as much as 2.5 stops)...
the pentax web site specifically mentions "abnormal metering with M lenses used in A..."
More than a few of us have latched on to the "foil trick". ie placing aluminium foil between the lens flange and the mount over the contacts. For me: new problem!! "Mirror flapping".
So far my best experience : foil trick but just the data contact thats the one at the six o clock position (approx).

Let me know how you get on.
07-15-2013, 03:19 PM   #15
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I have been corresponding with Marcus about this. My K-X doesn't behave the same way as Kozlok's.

For me, pressing the Green Button has no effect at all when an M42 lens with adapter K or a Pentax K T-mount (with either non-conductive surfaces or a lens whose mount does not touch the contacts) is on the camera.

However, touching the Exposure Compensation Button (as indicated on the Pentax support Web-site) when the camera is in M mode mostly does what I would expect pressing the Green Button would do; it adjusts the exposure according to the current aperture (when it works; sometimes the camera chooses an exposure of 0.3 seconds instead).

The non-intuitive behaviour, and the different behaviours of different Pentax (and Samsung) cameras, look to me to be evidence of software bugs, especially as the foil trick can lead to the camera displaying a bogus aperture value, which it clearly shouldn't.

Perhaps it would help to build a table of observed behaviours, camera models and firmware revisions?
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