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05-31-2011, 12:46 PM   #1
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Mounting and metering a Helios M42

Hi all.

I already own a Pentax A 50mm 1.4 which I can mount and meter on my K-x body properly, by setting the aperture ring to A and using the green button, the camera will move the lens blades to my desired aperture and meter as usual. No surprises there.

Today my Helios 44M arrived, in M42 screwmount together with it's adapter. I figured out how to mount on my body, all fine.

The problem is: on M mode, I set my aperture on the lens aperture ring (it doesn't have "A" setting, of course), but when I hit the green button the camera won't meter neither shot at my selected aperture, the lens just stays wide open.

If I'm not mistaken, the behavior shouldn't be this one. I think the problem may be that the lens is not being properly mounted with this adapter and the aperture pin is not being depressed, therefore nothing happens when I turn the aperture ring. Am I right?

If so, how should I mount M42 lenses with the adapter correctly?

Thanks


Last edited by hcarvalhoalves; 05-31-2011 at 01:23 PM.
05-31-2011, 02:12 PM   #2
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The aperture pin will never be depressed with most M42 adapters. You must use the A/M switch that is a feature of most auto-aperture M42 lenses. Fortunately, your Helios 44M has the switch. Other Helios 44M-n variants do not.

There are some stickies around somewhere regarding this, but here again are Steve's simple steps:
  • Make sure that Aperture Ring is enabled on your camera
  • Put camera in M mode
  • Flip the A/M switch on the base of your lens to the M position
  • Choose your shooting aperture and press the green button to meter the subject
  • Either flip the A/M switch back to A or manually change the aperture to full open to frame and focus
  • Stop down using the A/M switch (M) or manually (counting the clicks) and make your exposure
Repeat the last two steps as needed until either the light or the subject changes.

Very likely somebody else will post after me suggesting Av mode as a good alternative. You can do that, but be prepared for poor metering with significant underexposure wide open. This is due to quirks in the metering logic and is related in-part to the focus screen. Your K-x has correction logic that is applied in M-mode only. Outside of M mode YMMV.


Steve

P.S. I know the above sequence seems cumbersome, but that is how adapted M42 mount lenses have worked dating back to the first K-series bodies. It is easier and smoother in practice.
05-31-2011, 02:15 PM   #3
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Hi
Put the camera in Av Mode. Set the av adjustment to + 1.5 or 1.7
and Iso in auto.
Now just turn the F stop on the lens and the camera does the rest !
Same as any Takumar M42 lens.
Much easier than the M lenses.
05-31-2011, 03:10 PM   #4
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QuoteOriginally posted by stevebrot Quote
The aperture pin will never be depressed with most M42 adapters. You must use the A/M switch that is a feature of most auto-aperture M42 lenses. Fortunately, your Helios 44M has the switch. Other Helios 44M-n variants do not.

There are some stickies around somewhere regarding this, but here again are Steve's simple steps:
  • Make sure that Aperture Ring is enabled on your camera
  • Put camera in M mode
  • Flip the A/M switch on the base of your lens to the M position
  • Choose your shooting aperture and press the green button to meter the subject
  • Either flip the A/M switch back to A or manually change the aperture to full open to frame and focus
  • Stop down using the A/M switch (M) or manually (counting the clicks) and make your exposure
Repeat the last two steps as needed until either the light or the subject changes.

Very likely somebody else will post after me suggesting Av mode as a good alternative. You can do that, but be prepared for poor metering with significant underexposure wide open. This is due to quirks in the metering logic and is related in-part to the focus screen. Your K-x has correction logic that is applied in M-mode only. Outside of M mode YMMV.


Steve

P.S. I know the above sequence seems cumbersome, but that is how adapted M42 mount lenses have worked dating back to the first K-series bodies. It is easier and smoother in practice.
Thanks for the reply.

Actually, mine is a 44M-6, which unfortunately doesn't feature this A/M switch. By now, I figured out the only way people make it work "always-manual" is by gluing/bending the aperture pin inside.

Which is now making me wonder, what's the most elegant solution? I don't feel like disassembling a pristine lens or gluing stuff together, it will void the warranty. On top of it, messing with the M42 adaptor is a chore.

I'm also considering sending this lens back and getting a K-mount version of it instead. Better idea?

05-31-2011, 04:48 PM   #5
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hcarvalhoalves,
- refer to your camera manual on enabling aperture ring (on K-5 it's the 4th page in the custom settings menu, menu item #27). Get it enabled
- switch your baby to MF (manual focus). Otherwise your k-x won't trigger the shutter until it confirms you're in-focus (which sometimes doesn't work well; with MF it's really better to go with MF mode)
- using lens focus and aperture rings get it set to proper focus and DOF (this one is obvious and straight-forward)
- in manual (M) mode hit the green button to get cam's advice on proper exposure. From my experience it doesn't work in AV mode, though I didn't study it that deep
- adjust the exposure to your taste and experience
- go on with the shutter release button
- enjoy or repeat accordingly

Good luck,
Zig

P.S.
Re M42-K adapter: you can have the adapter spring removed and then using k-mount cap you can have it tightened to the lens and thus get semi-K mount lens. This have been discussed here on PF lots of time, you can go with 'm42 adapter spring' search.
05-31-2011, 08:52 PM   #6
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QuoteOriginally posted by hcarvalhoalves Quote
By now, I figured out the only way people make it work "always-manual" is by gluing/bending the aperture pin inside.
You don't have to use glue or bend the pin. The mount removes easily and you shim the pin with a short length of insulation off a fine gauge electrical wire or something similar. The result is a pin that is always depressed.


Steve
05-31-2011, 08:56 PM   #7
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QuoteOriginally posted by bobpur Quote
Set the av adjustment to + 1.5 or 1.7
and Iso in auto.
Can't comment regarding this approach on a K-x, but I can tell you that it doesn't work worth beans on a K10D or K20D. The meter response is not linear in Av mode except with A contact lenses. The camera manual uses less direct language, but the caveat is there.


Steve

(Nothing works on a K10D or K20D except chimping. Though some have reported good results with a *istD screen on those cameras.)
05-31-2011, 08:56 PM   #8
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Figured out how to use it correctly. Had to disassembly the lens and put something to hold the aperture pin in position. After that I was able to meter as usual, considering this lens is not preset.

EDIT: Right after posting I saw your response, stevebrot. That's exactly what I did to the pin!

My M42 adapter is still crap, though. I have to buy an original Pentax one.

This lens has a lot of character. It's razor sharp on the center (much more than the DA 18-55) starting at f/4 and I find the bokeh very unusual, pretty dreamy, gives a nice effect. I'm very happy with this acquisition. If I find a way to stick the adapter to it so I can mount/unmount like any K lens, it will see a lot of action.


IMGP2418 por hcarvalhoalves, no Flickr


IMGP2417 por hcarvalhoalves, no Flickr

Now I'm dying to take it out to shoot some night lights.

Thank you all for the help.


Last edited by hcarvalhoalves; 05-31-2011 at 09:08 PM.
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