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08-16-2014, 07:06 AM   #1
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help with M42 135 mm CZS lens on KX

I just acquired a 135 mm f/3.5 Carl Zeiss M42 lens. Initial hookup to the KX was a failure due to a (I assume) cheap adapter, so I have ordered a better one. In the meantime, I have the lens fitted up with a few nylon ties.

Anyway, although I know AF is impossible, should I at least be able to get focus confirmation from the camera once the lens is adjusted for best focus? How would I do it?

I'm also missing aperture metering. I can set exposure time in the camera, but the live view of the image isn't changing, nor is the metering.

Thanks for your help.

08-16-2014, 07:28 AM   #2
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The CZJ lens has an auto/manual switch which allows open-aperture metering with m42 bodies. For use with other cameras, it has to be in the m position. You should then be able to see the aperture blades move when turning the aperture ring. IF not, they might be stuck.
I don't own a kx, so I wouldn't know how to get focus confirmation. Metering should work via the green button.
08-16-2014, 08:22 AM   #3
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Yes, you should be getting focus confirmation. Look for the green hexagon in the bottom of the viewfinder. Depending on your menu settings you may or may not be getting the beep that signals when you are in in focus. On my K-x I turned the beep off because it became extremely annoying. Check menu, screen 1 in tools, and then select Beep to see if your In-focus beep is on or off.
08-16-2014, 10:37 AM   #4
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Here is how to mount it:
-switch lens to M
-make sure the little pin on the mount is depressed/pushed in and not hanging out (if lens is set to A, depressing the pin changes aperture; if it is set to M, the pin should be limp, but it can still get in the way)
-make sure camera is set to MF, not AF. The little screwdrive on the camera mount can bump into electrical contacts on electro m42 lenses, then they can't be screwed in all the way
-insert and rotate the m42 adapter until it clicks into place
-now screw in the lens, gently, making sure no electro or aperture pin is bumping into anything.
I think the Auto m42 lenses are made for old German m42 cameras and offer no special automation on Pentax cameras. Just be careful, because some cheap adapters have odd holes in them, where electro pins can get stuck! The genuine adapter is quite safe, I think

Hopefully it will work

Metering.. just select Av mode on camera. Now turn the aperture ring to be wide open for focusing. Once you focus, choose the aperture that you want. This will stop the lens down
and automatic metering should take a new reading and adjust shutter/ISO. You should focus wide open, because the DoF is the shallowest then. This should give you the most precise photos.

Focus confirmation
! Yes, Pentax DLSRs allow this! Its called catch in focus, or focus trapping. To activate it, you need to have the camera set to the correct AF mode (AF.S, AF.A - depends on your camera, check your manual). Then you need to go to Menu and near the end choose Catch in focus and enable it. (Oh, and while there, make sure "allow aperture ring" is enabled, too) The other thing you might have to choose is to make sure you have Focus priority and not Shutter priority. After you have all of this selected and the lens mounted, you need to switch camera from MF to AF. This allows the AF contact to be shortened. The problem is that some old lenses either don't cover the contacts (like Helios 44-2, because its mount is too narrow), have a plastic mount or are coated in non-conductive paint (which can usually be scratched off). Anyway, once all of these conditions are met, you should be able to press and hold the shutter without the camera going off. The camera will only go off if the shutter is pressed and AF gets confirmed. Only works for centre point. You can even hold the shutter button while you move towards your subject, or you can hold the shutter button while focusing, or you can hold the button and wait for the subject to walk into focus. Burst mode can increase your chances of getting a well-focused photo.
Another thing you can try, if your camera has the function, is Focus peaking in Live view. It works great with fast prime lenses. Its not focus confirm, but it makes getting the focus just right much easier
Yes, there are many things, yes its sounds complicated, but after you do it a couple times it gets easy and can be quite helpful With Pentax you get SR and focus confirm with lenses made in the 60s!

And when you input the focal length for the SR, make sure it is written as on the lens. Don't do any "equivalence" calculations, as that will give you wrong results. 135mm is 135mm. If you cannot select the exact number of the lens' focal length, choose the nearest wider one, so the SR undercompensates rather than overcompensates


Last edited by Na Horuk; 08-16-2014 at 11:00 AM.
08-16-2014, 11:20 AM   #5
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QuoteOriginally posted by PLC3 Quote
The CZJ lens has an auto/manual switch which allows open-aperture metering with m42 bodies.
Huh? The A/M switch is there to allow backward compatibility to bodies that don't support the automatic aperture (stop-down at exposure) time. TTL metering is always done stop down with M42 lenses on a Pentax dSLR.

With the K-x, I would suggest trying Av mode* using the following flow:
  • Set desired aperture on lens (switch in A position on lens)
  • Focus with lens wide open
  • Flip A/M to M position and note shutter speed. If too fast/slow, adjust the aperture to suit.
  • Make the exposure
This procedure is essentially similar to what you might do if your were shooting the same lens on a Pentax Spotmatic back in 1970.


Steve

* At least I think Av mode will work on that body
08-17-2014, 01:33 AM   #6
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Hmmm, sounds complicated! Anyway, I have to wait because the cheap M42 adapter I tried wouldn't lock into the Pentax, so I had to order a different, supposedly better, one. Once it arrives, I'll check back here for the tips. The focus confirmation will be the most important feature for me to have. If I can get that working, the rest won't be as important.
08-17-2014, 11:30 AM   #7
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QuoteOriginally posted by ctron Quote
The focus confirmation will be the most important feature for me to have. If I can get that working, the rest won't be as important.
No problem. It sort of comes with the package.


Steve
08-17-2014, 04:41 PM   #8
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Na Horuk, Thanks. I followed most of your instructions and was able to achieve focus confirmation with the KX. This will be a big help with astronomy especially as that's what I intend to use this set up for. I'm still awaiting the good M42 adapter to arrive, but for the focus tests I simply nylon tied the lens to the front of the camera for now.

Ok, didn't try Av mode earlier for metering, but just did now. Seems to work fine. Good, so now have the focus confirmation and proper exposure. Sweet. Thanks also Steve for helping out with the Av part.

Of course, for astronomy, I'll be on manual with dark frame disabled. The only thing I'll need is focus confirmation and thank goodness it works in debug mode as well.

08-18-2014, 02:36 AM   #9
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QuoteOriginally posted by stevebrot Quote
Huh? The A/M switch is there to allow backward compatibility to bodies that don't support the automatic aperture (stop-down at exposure) time. TTL metering is always done stop down with M42 lenses on a Pentax dSLR.
Steve, you are right. Thats what happens when I type in a hurry and don't really think your answer through
What I meant to say is obviously that the aperture stays open until you meter/ expose.
08-18-2014, 03:22 AM   #10
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Oh, astrophotography? Focus confirmation needs some light, ti cannot work in darkness. I am not sure the faint starlight will be enough. I suggest you find where the lens' infinity focus is and simply focus on the lens without even looking at the viewfinder.
Some adapters are thick and they change where the "infinity" is on the focus ring. Lenses that were poorly calibrated or fiddled with might also have the infinity somewhere other than the infinity mark

Edit: Also, 135mm for star photos will be difficult, because it is a tele lens. Stars move, and the more tele the lens, the less time it needs for starts to go from point sources to trails. This is why people use ultra wides for astrophotography, so you can have an exposure of 10, 20 seconds without startrails. I expect anything over 4 seconds will have startrails with an 135mm lens. You can use high ISO to compensate, but higher ISO creates more digital noise. Also, make sure you use the 2sec timer, so that pressing the shutter button doesn't cause blur. There are a couple threads about astrophotography, so feel free to look for them.
Good luck, and I hope to see some photos
08-18-2014, 03:38 AM   #11
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QuoteOriginally posted by ctron Quote
Of course, for astronomy, I'll be on manual with dark frame disabled. The only thing I'll need is focus confirmation and thank goodness it works in debug mode as well.
Confirmation? Do you think that focus on the moon and stars could be anything else short of infinity?
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