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03-11-2017, 04:13 PM   #1
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M42 Lens problem

Firstly - if this is in the wrong place, please move it :-) I couldn't work out a better sub-forum.


I have recently acquired (from difference sources) a couple of M42 lenses - A Carl Zeiss JENA Tessar 50mm F2.8 and a Kaligor 28mm F2.8.

Then I bought a cheap M42-PK adapter off that well known auction site and tried both out on my old K100.

The Zeiss seems to give reasonable results (see below for aprox 1/10 crop), but the Kaligor has trouble focusing. For a similar shot from the same position (about 6ft away from the bush) and with both on F2.8, I get very different results (again - below).

The Zeiss focus ring read where I would have expected, but I could only get the Kaligor to focus at all by setting it to infinity.

I know the lenses are very different, but I was expecting the focusing to be similar (given the same adapter was used).

Also - having tried different apertures, the Zeiss gives the expected focal length variation, but the Kaligor gives similar results at all apertures.

Is the Kaligor correctable / am I doing something wrong, or should I write it off (it was a give-away)?

Thanks,

Robin



Photos: Top - Zeiss, bottom - Kaligor. Shot on different days so the light was different (Zeiss was overcast and the Kakligor was sunny)

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03-11-2017, 04:17 PM - 1 Like   #2
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I could be wrong, but I suspect the Kaligor is a T-mount lens (also a 42mm thread, but with a slightly different pitch) which requires a T-mount to M42 (or T-mount to K) adapter. They're readily available...
03-11-2017, 04:44 PM   #3
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QuoteOriginally posted by BigMackCam Quote
I could be wrong, but I suspect the Kaligor is a T-mount lens (also a 42mm thread, but with a slightly different pitch) which requires a T-mount to M42 (or T-mount to K) adapter. They're readily available...
Thanks Mike,

The adaptor fits on both with no forcing at all (it is very smooth), so I think the pitch is the same.

How else would I tell the difference?
03-11-2017, 04:55 PM - 1 Like   #4
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Depending on the tolerance of the threads on the M42 adapter and the T-mount lens, it's often possible to fit the two together - even though they're different mounts

With T-mount lenses, the adapter for a native camera mount was normally held in place by one-to-four screws. Look at the lens threads, or just above the threads, to see if there's any evidence of screw marks, perhaps...

03-11-2017, 05:02 PM   #5
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QuoteOriginally posted by BigMackCam Quote
Depending on the tolerance of the threads on the M42 adapter and the T-mount lens, it's often possible to fit the two together - even though they're different mounts

With T-mount lenses, the adapter for a native camera mount was normally held in place by one-to-four screws. Look at the lens threads, or just above the threads, to see if there's any evidence of screw marks, perhaps...
The mount is proud of the flat of the lens back by less than 1mm, and there are 2 tiny screws.

Looks like I will be hunting for a T-mount adaptor in the morning :-)


Thanks Mike
03-11-2017, 05:04 PM   #6
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Sounds like that's the solution. You're welcome, Robin
03-11-2017, 05:05 PM - 1 Like   #7
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If the Kaligar 28 is anything like my Kaligar 35/3.5 preset lens, it is a T-mount and requires a T to M42 adapter. Without the T adapter the rear element is too close to the sensor and registration is off. This really makes it virtually impossible to focus.
03-11-2017, 05:11 PM - 1 Like   #8
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Some of the inexpensive M42 adapters and extension tubes thread pitch is somewhere in-between M42 and T-mount. I have a set of extension tubes that M42 and T-mount threads into them fine and dandy. However the tubes won't thread into the genuine Pentax adapter, bellows or bodies.

You could always try hand holding the lens unmounted and see how it focuses with some distance from the body. How thick is a typical T-adapter? 10-15mm I'd take a wild guess - to lazy to dig out an adapter and measure it.

03-12-2017, 01:03 AM   #9
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I have a T-mount adaptor on order now :-)

Not being familiar with this mount type, I was surprised how thick it is. That would explain the focus issue.

Just hope the lens is worth it.......
03-12-2017, 03:05 AM - 1 Like   #10
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QuoteOriginally posted by Robin CB Quote
I have a T-mount adaptor on order now :-)

Not being familiar with this mount type, I was surprised how thick it is. That would explain the focus issue.

Just hope the lens is worth it.......
A T-adapter is nice to have. You can play around with telescope adapters or fun mirror telephoto lenses
03-17-2017, 07:53 AM   #11
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Update:

The T-mount adaptor has arrived, but it doesn't seem to fit (see below).

The mount screws almost half way and the thread binds. I don't want to force it. I get the same result on my Ziess.

The packaging of the adaptor says T2-PK, so is the T2 different to the T-Mount?

Thanks,

Robin


Apologies for poor phone pics:




The mount without the adaptor:

03-17-2017, 08:04 AM - 1 Like   #12
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That is not a T-mount lens...The mount clearly has an aperture stop down pin, so it is M42...

Does the lens have an A/M switch? If not it is Auto only and will not stop down unless the pin is pressed...Using a normal M42 adapter it will alway be wide open.

There are M42 adapters with an flange inside to press the pin down, or one can be made. You can also gimmick the pin to keep it pressed down...
03-17-2017, 08:09 AM - 1 Like   #13
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Yep. That's definitely a M42 mount. Do you have a picture of the M42 / PK adapter you are using? It may have a flange that prevents infinity focus.
03-17-2017, 08:11 AM - 1 Like   #14
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QuoteOriginally posted by ripper2860 Quote
Yep. That's definitely a M42 mount. Do you have a picture of the M42 / PK adapter you are using? It may have a flange that prevents infinity focus.
From the description in the first post the Zeiss works fine, it stops down, and the other lens doesn't...
03-17-2017, 08:21 AM   #15
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QuoteOriginally posted by boriscleto Quote
From the description in the first post the Zeiss works fine, it stops down, and the other lens doesn't...
The OP has not specified (or I overlooked), but the Zeiss could be a 2-ring preset with no aperture stop-down pin. Just checking to see if the adapter could come into play.
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