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03-30-2012, 09:42 AM   #1
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Yashica lens question

I have a yashica auto yashinon 50/1.9 lens in M42 screwmount fit.
The problem is that it has no auto/manual aperture switch, and can only be used wide open on my
K100 d super. I have tried the tape method to hold the aperture pin down to gain manual aperture,
but the spring is too strong.
Can anyone suggest a non destructive way to gain manual aperture control? I don't mind a bit of
minor surgery. I have read that this is a rather good lens and would like to try it out properly.

03-30-2012, 12:45 PM   #2
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My Fujinon lenses have only auto mode. I got help earlier from this forum and flickr to open up and did a reversible modification.
In general, you need a small plastic tube, typical from electrical wire, approx 2mm, put it in the back side of the pin preventing it to spring back to auto mode.
I also done the same mod for several lenses. It takes only 2 minutes each. Use JIS screwdriver. Note where you have the aperture position and mount position to set it back.

Good luck
03-30-2012, 05:23 PM   #3
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Various M42 lenses are auto-only, lacking the M/A switch, and not all of them have easily-removable bases for hoanpham's mod. Besides Fujinons and your Yashinon, some Meyer lenses (like the Oreston and Domiplan) are so crippled, and the Meyers aren't easy to fix. The options are basically:

* Remove the base, perform the modification, and reassemble the lens.
* Glue the aperture pin down (I've done this with my Meyers).
* Don't buy auto-only lenses (I avoid Fujinons now).
* Learn to love shooting wide-open only.

The choice depends on what a lens cost, what it's worth, how good you are at dis- and re-assembling lenses, and whether you intend to keep it forever. Disposable lenses are easily and painlessly hacked or glued. Costly glass is something else. Good luck!
03-30-2012, 10:58 PM   #4
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QuoteOriginally posted by hoanpham Quote
I got help earlier from this forum and flickr to open up and did a reversible modification.
I have the same lens and although I did a bit of research, I have not been able to find an article how to disassemble the lens; possibly wrong search terms. If you still have a reference, it would be appreciated if you can post it.

I do understand the principle how to keep the pin in with a small sleeve, but disassembly is my issue at the moment and I was going to opt for the 'glue method'.

Thanks, WimS

03-31-2012, 06:47 AM   #5
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Thanks for the interest everyone. The problem I see with disassembling this lens is the backplate is secured around the edge by three of the smallest screws I have ever seen. I fear that I may not be able to re-fit them. I recently stripped and cleaned a Helios 44M and that was easy compared to this Yashica. The easy way to gain manual aperture may be the RioRico glue method.
04-05-2012, 12:52 AM   #6
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Flickr: Discussing Converting Fujinon lenses to manual aperture in M42 Fujinon lenses

Here is the article.
Use precission screw drivers on these tiny screws. It is very easy to re assemble. I mod mine with reselling value in mind. Glue may lowered the re sale value. I am not sure gluing is a faster mod, may be even longer. Unscrew mod had taken me less than 5 min each lens.

Last edited by hoanpham; 04-05-2012 at 01:00 AM.
04-05-2012, 12:57 AM   #7
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I forgot one more thing. Some fujinon lenses has a tiny metal sticking out to transfer aperture info to the body. On pentax digital bodies, it is on the way. If you do not want to use the dremel you need to press down the lens release button when mounting the lens. By cutting this little piece, the lens will function like any takumar in manual mode.
04-08-2012, 01:16 AM   #8
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QuoteOriginally posted by hoanpham Quote
Here is the article.
Unfortunately the Yashinon does not seem as easy as the Fujinon shown in the link. The latter looks more like the Tokina EL28/2.8 that I modified and is quite easy.

I have started with the Yashinon and documented it here. It is incomplete due to lack of proper screw drivers .

04-08-2012, 06:06 AM   #9
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Amazon has several sets of jis screw drivers. I got mine from them. Good article btw.
I also fail to open up my yashinon tomioka 55/1.2. I sent the lens to service after trying several times. Many screws were missing when i got it. Looking forward to read your article.
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