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10-30-2013, 07:50 PM   #1
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K-50 metering not working well with super-takumar screw mounts

Hi All,

I'm new to the K-50. So I hope I'm just doing something wrong. But I can't seem to get the K-50 to meter using older Super Takumar screw mount lenses. I've got a 35 mm and 50 mm Super Tak and neither of them meter worth a darn with the K-50. I've followed the guidelines here on the pentax forums as well as the same recommendation on Ricoh's website. But every time I press the green button to meter through the lens, which by the way I've tried it with the lens Auto/man setting set to manual as well as auto. And with the lens set to manual with various aperture settings I can see in the viewfinder more or less light accordingly. Regardless pressing the green button has no affect on the shutter speed setting. And the shutter speed it does select is really fast for the amount of light I know is coming into the lens. I've also tried pointing the camera towards more or less light, and then pressing the green button just to see if the metering alters the shutter speed. Still the shutter speed doesn't change. If i release the green button and then take the picture it's so underexposed the seen is almost completely black. I can barely make out the subject matter. However, I can manually set the shutter speed via the e-dial to what makes sense and it'll take a good picture. Am I expecting too much to have the camera do this for me with the green button? Is there only a limited set of lighting conditions when metering works accurately? Is there a way to calibrate the metering with a specific lens? Or is using the EV button the only option? For the record my ISO is not set to auto when I do this. Also if I look through the viewfinder I don't see the EV meter reflecting any change in exposure when pointing to more or less light either. Should the EV meter change, with the green button depressed, when pointing to/from more or less light?

10-30-2013, 07:53 PM   #2
Ole
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Have you set custom function number 22 "Using Aperture Ring" to "Enable"?

The Takumar should be set to Manual - the camera cannot stop the lens down.
10-30-2013, 08:01 PM   #3
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I dug up my M42 to K-mount adapter, mounted a Super Takumar, and actually get the same results as you.

But Av mode works. No need to push the green button. Just set the aperture with the lens in M mode and shoot.
10-30-2013, 08:21 PM   #4
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QuoteOriginally posted by Ole Quote
Have you set custom function number 22 "Using Aperture Ring" to "Enable"?

The Takumar should be set to Manual - the camera cannot stop the lens down.
Yes. I'm setting it to manual. I was reading in another thread here people had success with using live view to meter. I tried it and in live view, pressing the green button renders a successful metering and shutter speed. If I then turn off live view, the shutter speed set in live view stays set. Then you can take the picture successfully. There was a post from kozlok. He got with Ricoh and it sounds like they're investigating the issue at least on the K-30. My guess is some software engineer thought this would be a nice "feature." LIve view only metering that is. ;-) Sorry. I test software for a living. I hear, "It works as designed", way too much. The design needs to be fixed. No excuse for this. This K-50 is my first ever Pentax camera. And I didn't expect to see problems like this. Rather disappointing.

10-30-2013, 08:24 PM   #5
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Av mode is much more convenient - I just tested it as mentioned above - it works.
10-30-2013, 08:43 PM   #6
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QuoteOriginally posted by Ole Quote
Av mode is much more convenient - I just tested it as mentioned above - it works.
Yep. You're right. Av does work. But I think it should work in Manual mode too. Maybe this is the way the chose to implement it. In Av mode I cannot manually set the shutter speed with the E-dial like I can in M mode. So maybe they figured Manual mode is just that. Entirely manual including no metering. But then why would they make Live view metering work in manual mode? Oh well. At least there are some work-arounds. By the way, thanks Ole for the quick response on this one. Much appreciated.
10-30-2013, 09:04 PM   #7
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I don't have a k-50 so this might be wrong, but I thought I read on here someplace that there were issues similar to this if ISO was set to 'auto'. Instead of changing the shutter speed when you hit green button it changes the ISO. Try setting a fixed ISO and see if the behavior changes.

Just a thought, I might be way off base....
10-30-2013, 09:30 PM   #8
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M mode with fixed ISO

Yes. I am using fixed ISO. Not ISO auto. You definitely want fixed ISO.

Based on testing of my own and others (kozlok, Ole to name a couple) here's the behavior on metering with the K-50 and I'd guess the K-30. The below assumes you've set the aperture ring to enabled and M mode with theTvShift. And if using M42 lenses, or I would think many other older lenses, with the man/auto setting on the lens set to manual:

1.) Camera set in M mode:

A.) live view will meter with green button.

B.) Non live view will not meter with green button. The shutter speed is simply set to an approximate 1/ISO based on fixed ISO setting.

2.) Camera set in Tav, Av, Tv, or scn mode (each of which simply renders only Av mode, based on aperture ring enabled setting, as best I can tell):

A.) With either Live view or no live view the camera meters correctly via the green button. It'll even meter correctly if you extend the built in flash. It'll raise (make faster) the shutter speed accordingly.

3.) Camera set in U1 or U2 mode selected it gets even better . Still the camera is in Av mode but now you're a bit closer to fully automatic. i.e:

A.) If the ISO was fixed it will move to ISO auto and you can meter (green button) with or without live view. So in this mode both the ISO and shutter speed change based on the metering. And extending or not extending the built in flash unit will also affect the shutter speed/ISO. with or without live view.

So User modes 1 or 2 would be the way to go unless you're looking to have more manual control over the shutter speed/EV, etc.

So I humbly retract my earlier complaints. I think I see a method to the engineers madness.

Try it and let me know if you find the above to be true.


Last edited by ssokolich; 10-30-2013 at 09:39 PM.
04-06-2014, 02:40 PM   #9
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No manual metering in M mode with screw mt

I'm having the same problem. I made the recommended setting adjustments (allow shot without A lens, set green button to Tv shift in M mode), using screw mount Takumar with genuine Pentax M42-K adapter. Meters OK in Av mode with both fixed and auto ISO. In M mode, change F-stops on lens (set to M on lens), visually confirm lens opening is changing, push green button to meter, but shutter speed does not change. I think the lens is still usable, as using Av mode is actually a little more convenient as I don't have to press green button, just shutter, and I can also use auto ISO. However, I'm wondering why M mode does not work the way other people say works well.

On older K-mount lenses, like 50mm and 38mm M's, different behavior is found. Av mode works only at full open F-stop no matter what is set on lens (as expected). When M mode is used, needs to me on fixed ISO, then can meter with green button just fine. Thus behavior with M style K-mount lens is per Pentax instructions.

Also, when I do get metering to work, it seems to underexpose. I needed +1/3 or 2/3 EV comp to get what I thought was a well exposed shot.

Am I doing something wrong?
04-06-2014, 02:56 PM - 1 Like   #10
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QuoteOriginally posted by OldChE Quote
I'm having the same problem. I made the recommended setting adjustments (allow shot without A lens, set green button to Tv shift in M mode), using screw mount Takumar with genuine Pentax M42-K adapter. Meters OK in Av mode with both fixed and auto ISO. In M mode, change F-stops on lens (set to M on lens), visually confirm lens opening is changing, push green button to meter, but shutter speed does not change. I think the lens is still usable, as using Av mode is actually a little more convenient as I don't have to press green button, just shutter, and I can also use auto ISO. However, I'm wondering why M mode does not work the way other people say works well.

On older K-mount lenses, like 50mm and 38mm M's, different behavior is found. Av mode works only at full open F-stop no matter what is set on lens (as expected). When M mode is used, needs to me on fixed ISO, then can meter with green button just fine. Thus behavior with M style K-mount lens is per Pentax instructions.

Also, when I do get metering to work, it seems to underexpose. I needed +1/3 or 2/3 EV comp to get what I thought was a well exposed shot.

Am I doing something wrong?
Green button metering does not work as advertised when the mounted lens has a non-conductive base (most m42 lenses). This is one of several related issues known to affect the K-50 and other models that has been discussed at length on this site. Ricoh is aware, but there has been no relief in the form of firmware changes. The solution is to use Av mode and make do with somewhat unreliable meter readings -or- create a conductive surface to short the body contacts (I am not sure which ones).

Your underexposure with M42 lenses is part of the unreliable metering you can expect in Av mode. This behavior dates back to the K10D (my camera) and is a pain in the rear. You may find that accuracy improves when using moderate apertures (say f/4 or f/.6). At f/2 and wider you can expect significant underexposure of at least 1-2 stops.

As for non-A contact K-mount lenses not stopping down in Av mode...that is expected. M mode is required and you can expect fairly consistent and appropriate green button metering for those lenses in that mode. Are we confused yet?


Steve

Last edited by stevebrot; 04-06-2014 at 03:05 PM.
04-07-2014, 07:17 PM   #11
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QuoteOriginally posted by stevebrot Quote
Green button metering does not work as advertised when the mounted lens has a non-conductive base (most m42 lenses). This is one of several related issues known to affect the K-50 and other models that has been discussed at length on this site. Ricoh is aware, but there has been no relief in the form of firmware changes. The solution is to use Av mode and make do with somewhat unreliable meter readings -or- create a conductive surface to short the body contacts (I am not sure which ones).

Your underexposure with M42 lenses is part of the unreliable metering you can expect in Av mode. This behavior dates back to the K10D (my camera) and is a pain in the rear. You may find that accuracy improves when using moderate apertures (say f/4 or f/.6). At f/2 and wider you can expect significant underexposure of at least 1-2 stops.

As for non-A contact K-mount lenses not stopping down in Av mode...that is expected. M mode is required and you can expect fairly consistent and appropriate green button metering for those lenses in that mode. Are we confused yet?


Steve

Yup, my head is spinning
04-07-2014, 09:10 PM   #12
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QuoteOriginally posted by rwingsfan Quote
Yup, my head is spinning
Good, that is the expected behavior.


Steve
04-30-2014, 07:22 PM   #13
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QuoteOriginally posted by stevebrot Quote
Green button metering does not work as advertised when the mounted lens has a non-conductive base (most m42 lenses). This is one of several related issues known to affect the K-50 and other models that has been discussed at length on this site. Ricoh is aware, but there has been no relief in the form of firmware changes. The solution is to use Av mode and make do with somewhat unreliable meter readings -or- create a conductive surface to short the body contacts (I am not sure which ones).

Your underexposure with M42 lenses is part of the unreliable metering you can expect in Av mode. This behavior dates back to the K10D (my camera) and is a pain in the rear. You may find that accuracy improves when using moderate apertures (say f/4 or f/.6). At f/2 and wider you can expect significant underexposure of at least 1-2 stops.

As for non-A contact K-mount lenses not stopping down in Av mode...that is expected. M mode is required and you can expect fairly consistent and appropriate green button metering for those lenses in that mode. Are we confused yet?


Steve
Steve - Sorry it has been so long since your post, but thanks. When I read your comment about the non-conductive mount, I remembered reading some discussions here about that (before I got my K-50 and the lens mount adapter). Given all these issues, would metering be much easier and more accurate if I got some Pentax-A lenses instead of the M42 or Pentax-M lenses that I do have? Or even some of the earlier autofocus Pentax-F lenses? When I started buying old lenses on Ebay I stayed away from Pentax-A since I could not also use them on my Pentax Spotmatic (which I've used since I got it new in 1970) nor with an adapter on my Sony NEX 5N (which by the way meters just fine in almost any mode with the M42's and Pentax-M's in stop down mode).
05-01-2014, 10:21 AM   #14
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QuoteOriginally posted by OldChE Quote
Given all these issues, would metering be much easier and more accurate if I got some Pentax-A lenses instead of the M42 or Pentax-M lenses that I do have?
Yes, any lens having the "A" contacts on the mount will allow you to use all metering modes on your camera. Your Pentax-M lenses should work just fine using stop-down (green button) metering in M mode. As for your NEX...I don't own one, but it is my understanding that support should be the same for any K-mount lens having an aperture ring. Those without require a special adapter with an aperture ring as part of the adapter.


Steve
05-01-2014, 11:10 AM   #15
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QuoteOriginally posted by OldChE Quote
(which by the way meters just fine in almost any mode with the M42's and Pentax-M's in stop down mode).
and I can say the same about my Panasonic Lumix G1. But thats one of the +1's of mirrorless. Metering is straight off the sensor, not intermediate mirrors etc.
BTW metering inaccuracies aren't limited to M and M42. I was using sigma miniwide 28mm and tokina RMC 28mm the other day, both PKA, in Av. Consistently a 1eV difference in metering between the two. I was always about +1ev with the RMC, and spot on or -0.3eV with the sigma.
Go figure....

I find I have to learn the metering relationship between my Kr and each MF lens, they are all a bit different. But as Steve says the big PITA is the huge inaccuracies with M42. I am normally stuck at or close to +3eV with M42, though lately I have been experimenting more with a T-mount with anodising taken off to make electrical contact, and with a plated rather than black rimmed adapter. But then we're back into mirror flopping..
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