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kyoei acall 35mm 3.5 optical construction issue
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PostPosted: Sat Sep 09, 2023 11:32 pm    Post subject: kyoei acall 35mm 3.5 optical construction issue Reply with quote

I bought a copy of this for cheap because the helicoid was stuck. I figured I could get it to work or worse case scenario use it as is with a helicoid adapter. I got the lens and the focus ring was loose from helicoid. I loosened the grub screws that held the exakta mount in place, and took that apart then the focus ring to get a good grip on the helicoid and after some armstrong technique using a jar loosening rubber grip the helicoid broke loose. Worked it back and forth and it seemed OK. I started to put it back together and was figuring out how to line up the helicoid ring at infinity and was dismayed that I could not get infinity. Or any other image. At any distance from the sensor. Thinking maybe a lens element had got turned over swapped the back element then the second element the both the back and second element. The front element seems pretty clearly a concave backed thing so that seems unlikely to be the issue. the third element is in a brass housing and is held in with an aluminum ring with no lugs. I couldn't get that apart. Any ideas?

PostPosted: Sun Sep 10, 2023 1:55 am    Post subject: Reply with quote

PostPosted: Tue Sep 19, 2023 3:07 pm    Post subject: Reply with quote

I think I figured it out. It seems the very front element is missing. I purchased it "as is" with note that the focus was stuck. I assumed worstcase scenario was I could use it with helicoid adapter. Oops. I found a site that mentioned FIVE elements. I only got 4. If anybody happens to have a copy with bad body, aperture or 4 other elements I could help. Alternatively I could use a good front element from somebody's bad lens. Klaus? Could you move this to the lens wanted section?

PostPosted: Tue Sep 19, 2023 8:02 pm    Post subject: Reply with quote

It's a long shot, but Kawanon (apparently) carried on using the same optical arrangement for quite some time after Kyoei disappeared. They sold that lens under many different badges. The lens is well known now as being good for UV photography due to the use of lower grade glass in the design, so there is the unfortunate phenomenon of various sellers trying to inflate the price, but if you lurk a while, you will find one for around the $20 mark. Having said that, it may or may not work.

I have both the Kawanon and Kyoei variants so if I get time soon I can confirm if they are indeed the same or similar.

PostPosted: Tue Sep 19, 2023 9:20 pm    Post subject: Reply with quote

Ah thanks, was unaware of that connection. I knew of Petri and Kurabayashi. Apparently some spiratone and other 3rd party maker labelled versions exist but without the lens in hand I am reluctant to try that approach.

PostPosted: Wed Sep 20, 2023 11:26 pm    Post subject: Reply with quote

The front elements are the same or very similar, I just tried swapping them. It fits maybe not quite as snugly, but there's no play. This picture is taken on a Soligor badged Kyoei 35/3.5 wide open with a front element from a Kawanon lens. If anything, the corners were slightly better with the swapped element. I didn't bother to confirm whether all the other elements are identical, there were 5 total though.

However if you want to go that route, first make sure the retaining screw collar thing on the Kyoei lens isn't missing or you'll need to find another way to hold the front element in place.