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10-26-2014, 03:25 PM   #1
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Super-Takumar 50 inaccurate aperture

Hello!

I have Super-Takumar 50/1.4. I like it very much, but now I have a problem with that lens.

The aperture seems to be inaccurate. When I change the aperture value to 16, it seems to step down about f/8 or like that.
However, the focus seems to be inaccurrate too, I've lost the sharpness about f/4-5.6. This is very annoying.

I've disassembled the lens, the aperture mechanism doesn't step down the blades to 16, but if I remove the optical block and move the focusing knob on the block, it steps down to minimum aperture without any resistance. The blades are free from oil, grease or else, and the back pin of the aperture moves free too.

How can I solve these problems?

Norbert

---------- Post added 10-26-14 at 11:28 PM ----------

Ah, focusing knob, I meant to aperture knob, sorry for the mistake.

10-26-2014, 03:40 PM   #2
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maybe these will help:


Pentax 50mm f/1.4 strip-down instructions
10-26-2014, 03:50 PM   #3
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Sounds to me as if the lens had been disassembled and re-assembled incorrectly.

Check youtube to see if there are any videos on tearing down this lens and the Pentax Disassembly Lens Database
https://www.pentaxforums.com/forums/114-maintenance-repair-articles/179884-pe...-database.html

If the aperture ring moves without the usual click stops I'd say the lens was worked on by some that probably didn't know what they were doing. Of course the detent ball bearing may have been deliberately removed.
10-27-2014, 07:08 AM   #4
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In case you didn't already see it in the Pentax Lens Disassembly Database that Not a Number mentioned, This tutorial I made should be helpful:
JB Media | S-M-C Takumar 1.9 85mm Refurbish
The procedure for setting up the diaphragm is pretty much the same for both lenses.

As far as not having any resistance, is the click-stop ball missing? JB Media | S-M-C Takumar 1.9 85mm Refurbish

10-27-2014, 12:59 PM   #5
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Original Poster
The issue came before I disassembled the lens.
After dis- and reassembly (about a half of a year), the problem seems to be solved, but it came again about 1 month.
I can change the aperture step by step, so the clicking mechanism works as it needs to. Maybe the bearing can cause the problem, but it's pretty strange that the aperture lever arm (in the lens barrel) moves correctly. I think something in the optical and aperture block causes the aperture issue.
The focusing seems to be an incorrect placement of the optical block (but the screws are tightened enough, so idk). Maybe I get it apart, and searching things that can cause these problems.
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