[cyclone3d]

I've just received a Kenko 85mm f:2.5 Soft lens.

It came with a Sony adapter which I thought was T2 threaded.

However, it is not T2 thread, but M42 thread.

With an M42 to K adapter, the lens will not focus close and also focuses past infinity.

Looks like there must have been a different adapter available for this style lens but I am not having any luck finding one.

Has anybody run into this before?

I'm guessing an M42 extension tube of about 7-8mm would take care of the focusing problem if I can't find the correct adapter.

Edit: Shortest M42 extension tube I am finding is 9mm.
T2 extensions are available as short as 7mm.

Uggghhh.

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Last edited by cyclone3d; 09-19-2022 at 03:58 PM. Reason: add info

[UncleVanya]

Is your adapter the actual Pentax adapter rather than a copy?

It’s typically possible to adjust infinity and consequently the accuracy of close focus. This requires opening the lens.

[cyclone3d]

Is your adapter the actual Pentax adapter rather than a copy?

It’s typically possible to adjust infinity and consequently the accuracy of close focus. This requires opening the lens.

I do have an original Pentax but I was using an aftermarket that bumps the lens out about 1mm further because it is the style that doesn't lock to the body but instead has a flange with the k-style hole in it for it to click onto the body.

The Pentax one would make the focusing issue even worse.

Maybe one of the 9mm extension tubes would work perfectly with an original Pentax adapter.

I kinda doubt I would be able to get 7-8mm of focus adjustment by taking the lens apart to adjust it. Any lens I have ever taken apart is lucky to have 1-2mm worth of adjustment.

Just took the M42 mount ring off of the lens and it looks like the only way to "adjust" it would be to shorten the metal tabs that stop it from going any further. Not going to even try that as it would compromise the focusing mechanism.

[K-Three]

So it looks like this lens has a different mounting system altogether?
https://photo.site-j.net/english/report/mc85.html
Not sure if this writer is mixing up T-mount, and this "P" Mount, but sure seems odd that the lens natively fits M42 thread, but has the wrong flange distance?
Sounds like an interesting bit of glass if you can find or make the right mounts for infinity focus

[cyclone3d]

So it looks like this lens has a different mounting system altogether?
https://photo.site-j.net/english/report/mc85.html
Not sure if this writer is mixing up T-mount, and this "P" Mount, but sure seems odd that the lens natively fits M42 thread, but has the wrong flange distance?
Sounds like an interesting bit of glass if you can find or make the right mounts for infinity focus

Yeah, I saw that page when I was looking up the lens before I ordered it. Sounded like it was T-mount.

I did find a seller on AliExpress that sells M42 extension tubes with 1.0mm thread pitch in the length of 4,5,6,7,8,9mm. Figure the 7,8,or 9mm will work just fine though I don't really trust the paint on them as they don't look flat black.
Aluminum M42-m42 42mm X 1mm Screw Mount Extend Tube Ring Adapter - Lens Adapter - AliExpress

I did do a little bit of testing with a T2 mount which of course only goes on about 1/2 way due to the thread pitch difference and I don't exactly agree with the review on that page as at f8 it seems pretty sharp for a soft focus lens. I wonder if that person was having a front/back focusing issue.

[Not a Number]

Well good luck with those tubes from AliExpress. A lot of times those cheap tubes the thread pitch is in-between 1 and .75. I bought a cheap set from Amazon. My lens all thread into them okay and the tubes thread together ok but they won't thread into two of my three genuine Pentax adapters and it sort of threads into my Pentax M42 bellows.

The return shipping was more then what the tubes cost so the seller said keep the tubes and refunded my money.

Sounds like Kenko used propitiatory adapters for that lens. Bad choice of same diameter and thread as Praktica /M42.

[cyclone3d]

Hopefully they work... I did locate some weird 5mm extensions from Zeiss but they aren't cheap and not super convinced they would be long enough.

Just found a set by Wirgin ? For Edixa Reflex (German made) that comes with a 2mm spacer and 6, 13.5, and 29.5mm tubes. Ordered that as well since it was fairly cheap and is bound to be way higher quality than the AliExpress tubes.

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Last edited by cyclone3d; 09-19-2022 at 09:57 PM.

[kypfer]

I've just received a Kenko 85mm f:2.5 Soft lens.
It came with a Sony adapter which I thought was T2 threaded.
However, it is not T2 thread, but M42 thread.
With an M42 to K adapter, the lens will not focus close and also focuses past infinity.
Looks like there must have been a different adapter available for this style lens but I am not having any luck finding one.
Has anybody run into this before?

My guess is that the lens has been disassembled and incorrectly re-assembled, (or deliberately mis-aligned for some other purpose).
I have bought a couple of M42 lenses with this "focus past infinity" problem.
Rather than mess about, I simply put up with it and use extension tubes as necessary if I specifically want to use that lens for close-up work.
Good luck

[kwb]

Edit: Shortest M42 extension tube I am finding is 9mm.
T2 extensions are available as short as 7mm.

Uggghhh.

I googled “M42x1 extension tube” and this was the second hit. The shortest one in the kit is 7mm.
https://www.wemacro.com/?product=m42-extension-tube42mm-x-1-0
I’ve never bought anything from this company BTW.

[Not a Number]

I googled “M42x1 extension tube” and this was the second hit. The shortest one in the kit is 7mm.
https://www.wemacro.com/?product=m42-extension-tube42mm-x-1-0
I’ve never bought anything from this company BTW.

Those look exactly like the useless ones I bought on Amazon. I wouldn't waste my money on them.

Edit: Too lazy to take and post a picture of the crappy tubes but the are identical in appearance. The note I folded up inside them gives the lengths of the tubes I measured as 27, 14 and 7mm. They will work if they will thread into the camera or adapter. There is no guarantee the threads will fit.

[cyclone3d]

The Edixa tubes arrived today and the 6+2 is too short and the 13.5 is too long.

I really don't think the lens has been disassembled before unless it was done with professional tools. This lens looks pretty much brand new. The iris blades have pretty much no wear on them either.

I guess I'll have to wait until my AliExpress set gets here and see if I can get the correct length that way. That will give me 1mm increments from 4mm to at least 19mm.

Edit... There is pretty much no way that this lens was disassembled and reassembled wrong. The focus is a simple helicoid that moves the whole lens assembly closer and further away from the body.

Found a page that mentions that when using it with an m42 adapter for an Olympus E-300 (m4/3 ?) that a pentax m42 #1.. says about 9mm gets almost infinity. Translated from Japanese so not sure if that means it still focuses past infinity or if the extension is too long and it can't focus to inifinity.
https://blog.goo.ne.jp/oban3/e/afbe72d9da0e08b0a810e8b58a12cc2d

[Not a Number]

These guys will build a custom adapter for you. The shortest tube they can make with M42 to M42 is 7mm. They are not cheap, the use aircraft aluminum and anti-reflective coat ribbed inside and anodize the outside of the adapters. The 7mm custom is $106 USD. $108 for an 8mm.

https://www.preciseparts.com/ppmain/adapter.html

[cyclone3d]

These guys will build a custom adapter for you. The shortest tube they can make with M42 to M42 is 7mm. They are not cheap, the use aircraft aluminum and anti-reflective coat ribbed inside and anodize the outside of the adapters. The 7mm custom is $106 USD. $108 for an 8mm.

https://www.preciseparts.com/ppmain/adapter.html

8mm is too short and their ain't no way I am paying to have a custom tube made.
If the AliExpress tubes are not flat blacked out, that is simple enough to fix with a can of spray paint.

[Not a Number]

The smallest tube in the Asahi Pentax Extension and Auto Extension tubes is 9.5mm.

If the tube gets you within +/- 1mm you should be able to adjust the lens in the normal fashion. Disconnect the focus collar from the helicoid, Adjust the focus by turning the helicoid. Align the markings on the focus collar. Re-attach the focus collar/barrel. The collar is usually connected to the helicoid by screws on the front of the lens barrel (under the name ring and filter thread ring) or under the rubber grip.

[cyclone3d]

Received the Chineseium extension tubes today. They seem of good enough quality and the thread pitch is fine for both lenses and M42 to K adapters.

The 9mm extension + aftermarket M42 to K adapter (one with a large lip and hole for the camera's lens release tab to lock into gives me right at infinity focus... or at least the camera says so when I was focusing on a cell tower a ways down the road.