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Lens Help


lost cat

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I recently got my hands on a couple of lenses.

 

Lens 1 is a Votar branded 35mm f/3.5 which has been mentioned elsewhere in this forum as being good for UV:

 

http://www.ultraviol...__fromsearch__1

 

When i tried it out however I found at best it can only focus to about 3 feet from the subject. It has a permanent M42 mount. I don't know anything about the history of this lens but overall it seems to be in decent shape. I can see some scratches near the wrench notches so I suspect at some point it was serviced and incorrectly reassembled.

 

Lens 2 is a Tokina 35mm f/3.5 with a similar problem but not quite as severe. This one has a permanent M47 mount with a M42 adapter.

 

Does anyone have suggestions on which elements I should be looking at or other ideas on how to get these lenses working correctly?

post-90-0-23179100-1464714931.jpg

post-90-0-08501600-1464714939.jpg

post-90-0-71680500-1464714944.jpg

post-90-0-33491700-1464714954.jpg

post-90-0-80872900-1464714959.jpg

post-90-0-65974900-1464714965.jpg

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Had the camera only been the Canon, my guess would be bad adapters. However, with a native Pentax into the equation, the enigma deepens ... Some of the non-specialised lenses used for UV have a massive focus shift, but I assume your tests so far have been in visible light.

 

Try remove the M42 and push the lens flush to the camera mount. Can you get infinity focus this way?

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Had the camera only been the Canon, my guess would be bad adapters. However, with a native Pentax into the equation, the enigma deepens ... Some of the non-specialised lenses used for UV have a massive focus shift, but I assume your tests so far have been in visible light.

 

Try remove the M42 and push the lens flush to the camera mount. Can you get infinity focus this way?

 

Yes, I think so with the Tokina on the Pentax. I estimate another mm or two into the body further than the M47->M42->PK mount combination allows is about right. This may simply call for a M47->PK mount solution.

 

As to the Votar I can't push it into the body far enough to get close to infinity focus. I can't tell for sure but the image looks like it would be distorted if I could get it focus.

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I think that the Tokina M47 mount will need a flange focal distance of 55mm.

Pentax requires an FFD of 45.46mm.

So you need some extension to enable the Tokina to reach an infinity focus on your Pentax camera.

 

How that is best accomplished, I don't know because I don't know exactly what your M42 adapter does to the Tokina by way of extension. Does the M42 adapter extend past the original M47 mount? If it does not, then you need 9.54mm of extension. So you try to find a mount adapter or an extension tube which gives you that extension.

 

Adapters for an FFD of 55mm are usually sold under the name "T" or "T2" adapters. So you could try to look for a Pentax K-mount (body) to T2 (lens) adapter.

 

I'm assuming your "ist" camera has the Pentax K-mount.

 

WARNING: There is the T2 thread which is 42mm x .75 and then there is the M42 thread which is 42mm x 1.0.

Before you buy anything please determine which 42mm thread your lens has.

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This is in conflict with the original post. The Tokina was said to focus just to about 1 m instead of infinity. That assertion implies the lens already had overly long extension and this should be shortened. Adding even more certainly is not the proper solution.

 

A reversed rear element probably would make the entire image horribly soft, showing lots of CA, vignetting, or perhaps not. Some lenses only get softer corners. Examining the rear lens for obvious signs of reversal might be a good idea, although the scratches seen on the rear element by the lens portrait indicates the configuration has been as shown for a long time.

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This is in conflict with the original post. The Tokina was said to focus just to about 1 m instead of infinity. That assertion implies the lens already had overly long extension and this should be shortened. Adding even more certainly is not the proper solution.

 

A reversed rear element probably would make the entire image horribly soft, showing lots of CA, vignetting, or perhaps not. Some lenses only get softer corners. Examining the rear lens for obvious signs of reversal might be a good idea, although the scratches seen on the rear element by the lens portrait indicates the configuration has been as shown for a long time.

 

To clarify the Tokina has a native M47 to 42mm screw thread . The 42mm threads are sloppy (and short) enough for it to completely screw on to either standard M42 1.0 or T-mount 0.75mm pitch threads.

 

The M42->Body adapters I am using put the base of the M47->M42 adapter essentially flush with the body of the camera with the rear element flush with the back of the Canon adapter or projecting *just* past the back of the PK adapter into the body of the Pentax.

 

PK adapter:

 

post-90-0-65345400-1464742618.jpg

 

I did take a few visible pictures at infinity with the cameras just to make sure it wasn't a viewfinder focus issue.

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To clarify: M47 historically has a 55mm FFD. I don't know how Jim's Tokina has been altered by addition of its adapter. It is possible that it is not an M47-to-M42 adapter but rather an M47-to-T (or T2) adapter which is why I mentioned the thread pitch and asked about whether it extends the lens or not. A thread gauge should be used to find the actual pitch of this particular 42.

 

Somewhere there are some instructions for determining the FFD. I will try to find them.

 

Forgot to add: If the lens is only 1mm "off", then adjusting the infinity setting on the lens may fix it.

But I'm going to be surprised if it turns out that this lens really has an FFD of 45.46mm. :)

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Your Votar is a re-branded Kyoei/Kuri, made by Kyoei/Acall.

I don't know what to expect with your camera, but without an M42 adapter with a built in infinity focus lens (on my Nikon) Kyoei/Kuri 35mm will not focus very far (which comes in handy for close up shots).

I use a cheap M42 adapter with a built in infinity focus lens, uncoated I am sure, and such it will transmit as low or lower than the lens does, which is also true of many cheap uncoated close up filters.

When I want to get closer, I use an M42 adapter with no infinity focus lens.

The Votar should probably be a very good lens for UV, and probably very little focal shift. You might ask Alex if he has tested and compared the Votar with the Kyoei/Kuri versions.

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enricosavazzi

I am not sure I have done the following with a Kyoei Acall or clones thereof (I may have, but don't remember for sure), but it has worked for me with a few other legacy lenses where the lens assembly (inner barrel) rotates when you turn the focus ring. The procedure is partly similar, but not the same, for lenses where the lens assembly does not rotate when you turn the focus ring.

 

First you need to separate the lens assembly (which includes all optical elements within a metal barrel that rotates when you turn the focusing ring) from the outer barrel of the lens. The two parts slide helically against each other along a machined set of spiral threads. The threads are abundantly greased to dampen the focusing movement, so your hands will get messy if you touch the threads, plus you should not remove/replace the grease unless it has become too stiff. So, keep your hands clear off the threads.

 

The lens assembly is prevented from completely screwing out of the barrel by a stop screw or other removable stop. To get to this stop mechanism, you usually have to remove the lens mount (bayonet or thread) and/or some of the external metal rings above or below the focus ring. They are usually kept in place by small screws. Do not touch any of the retaining rings that keep the front and rear optical elements in place, instead.

 

Completely unscrew the lens assembly out of its focusing thread, but stop at this point and do not move the lens assembly away from the barrel, do not rotate it either.

 

The focus thread typically uses multiple parallel threads, not just one continuous spiral thread like common screws. So rotate the optical assembly a little against the edge of the lens barrel (something like 10 to 30 degrees) until you can re-insert the lens assembly into the next thread set. Test the lens. If the focus problem has become worse, disassemble the focus thread again, rotate the lens assembly in the opposite direction, skip the next thread (i.e, the one originally used by the assembly) and re-engage it two threads away. Test the lens.

 

Continue shifting to the next thread and testing until you overshoot the infinity focus, then if necessary back up by one thread.

 

Reassemble all the other barrel parts. Done. The engravings of the focusing scale may no longer be accurate, but the lens should focus to infinity (and sometimes a little beyond) if you tested correctly during the procedure.

 

This method is also handy if you have a camera that has been converted to multispectral by removing the built-in filter, without replacing it with a UV- and IR-transparent window. In this way you can compensate for the changed length of the optical path between lens and sensor, which otherwise makes it impossible to focus at infinity with lenses that had been factory-calibrated for use on unmodified cameras.

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I fully agree with Enrico's recommendations, however, I have to warn that the focusing mechanism in Kuri/Kyoei (as well as in this Votar) was more difficult to work with comparing to other lenses I've disassembled and re-lubricated. If you go this route, make sure you make good notes and pictures of disassembly process.
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Dissembled all of the optical elements in a Kyoei/Kuri (not including aperture and focus mechanism).

 

Front section unscrews from lens body:

post-87-0-08387900-1464797045.jpg

 

Front elements dissemble (keep notes on which direction the elements are installed):

post-87-0-13194600-1464797146.jpg

 

Rear element also removed from lens body:

post-87-0-37122500-1464797213.jpg

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To clarify: M47 historically has a 55mm FFD. I don't know how Jim's Tokina has been altered by addition of its adapter. It is possible that it is not an M47-to-M42 adapter but rather an M47-to-T (or T2) adapter which is why I mentioned the thread pitch and asked about whether it extends the lens or not. A thread gauge should be used to find the actual pitch of this particular 42. Somewhere there are some instructions for determining the FFD. I will try to find them. Forgot to add: If the lens is only 1mm "off", then adjusting the infinity setting on the lens may fix it. But I'm going to be surprised if it turns out that this lens really has an FFD of 45.46mm. :)

 

So would I. I think this is a standard M47 with a standard 55mm FFD. To get infinity focus this lens needs to move towards the sensor, not away as would be the case with a longer adapter.

 

I did look into adjust the infinity setting but the focusing ring is bottoming out against the aperture setting ring at infinity. A more in depth look is needed but I don't want to go too far down the wrong rabbit hole.

 

Dissembled all of the optical elements in a Kyoei/Kuri (not including aperture and focus mechanism). Front section unscrews from lens body: post-87-0-08387900-1464797045.jpg Front elements dissemble (keep notes on which direction the elements are installed): post-87-0-13194600-1464797146.jpg Rear element also removed from lens body: post-87-0-37122500-1464797213.jpg

 

Very nice pictures, thank you! I didn't want to call my Votar a Kyoei/Kuri "clone" but my Votar does look like a less clean version of what you are showing here. I'll give it a good cleaning as soon as I can block aside a bit of time.

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enricosavazzi

A lens of this age should not be that clean inside, so I think you can safely assume that a previous owner has recently disassembled the lens completely and cleaned everything. Therefore, it does not really matter that you have done it again. All optical elements had already been rotated and possibly shifted sideways (if the retaining mounts are loose enough to allow it, which they often are) with respect to the original factory-made alignment.

 

Otherwise, unless necessary to clean out excessive dust or molds, there is no good reason to disassemble the optical elements, because this destroys any factory alignment of the optical elements (which may or may not have been made by the maker, or made with good enough equipment, or made carefully enough to matter).

 

In general, elements of mass produced lenses are not individually aligned. The lens is simply assembled from randomly chosen, randomly rotated elements and then tested summarily for image resolution. The specimens that fail the test are then disassembled and the individual optical elements returned to the respective bins. Eventually (unless one of the elements is so much out of specs that it can never work well), a lens will be assembled from elements again randomly chosen and randomly rotated, that by pure chance it will perform well enough to pass the test. Still, by disassembling and reassembling the elements, they may accidentally be rotated/shifted (usually) into an "unlucky" combination that gives a similar or poorer IQ, or (very rarely) you may win the lottery and randomly achieve a combination that gives you a better IQ than before.

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As Bjørn points out the rear element reversal could result in various distortions which you observed may be the case for the Votar. It is probably the easiest thing to eliminate before opening the front.

 

I suggest perhaps the next easiest thing might be to check if the entire front section is screwed all the way in. Steve, if it weren't what would be the result?

 

Enrico makes a very good case for not pulling a functional lens apart. However yours is not functional, so it may be down the rabbit hole you go.

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If the front element(s) are not entirely screwed home, they probably act to make the optics very near-sighted.
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I have never tried moving the front optics front/back.

The Kyoei/Kuri lens focus ring moves the rear optic front/back. The aperture and front optics stay stationary. (incorrect)

So is the question this, "I found at best it can only focus to about 3 feet from the subject" ?

That is what mine do on my Nikon, if I don't use a M42/Nikon mount converter with a built in infinity focus lens, so that is all I think it is.

Your M42 mount is removable, it has three little screws around its outside that will release it.

Inside there may be an indentation around the back of the lens that those fit into or there may be 46mm threads on the back of the lens body, these come is various arrangements.

For example, I have an Exakta mount on one Kyoei, which is removable, and the lens has 46mm threads, which I convert to M42 with a 46mm>39mm+39mm>M42mm, it works.

However, with your lens with the M42 threads, the close focus would be normal if you are not using a mount with a built in infinity lens.

You may still need to adjust the focus mechanism.

 

Here is the M42-Nikon-Infinity-Lens I have, etc.:

post-87-0-02372800-1464914893.jpg

 

post-87-0-90142300-1464914915.jpg

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Unlike M42 to Nikon F, neither the M42 to PK nor the M42 to EOS adapters require corrective lens to focus INF.
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The Kyoei/Kuri lens focus ring moves the rear optic front/back. The aperture and front optics stay stationary.

 

In Kyoei/Kuribayashi and similar lenses, focusing mechanism moves the entire optical assembly.

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In Kyoei/Kuribayashi and similar lenses, focusing mechanism moves the entire optical assembly.

 

Yes, that is correct. My mistake, sorry.

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Lost Cat, I just now tried moving the front elements front/back, and found that if they are not screwed all the way in this does move the focus near.

Also, I note that in the photo of your lens, the 'red dot' is noticeably further forward than all of my Kyoei/Kuri lenses, so it may very well be that your front elements are not screwed all the way in,

which would indeed shift the focus closer than it should be.

 

Also, for those who are hesitant about dismantling the lens optics of a Kyoei/Kuri 35mm, here is a drawing of one of mine.

The Kuri is suppose to be 5 elements, so it may be that one of these is two elements glued together. Perhaps Alex knows.

post-87-0-89170800-1464936058.jpg

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PK adapter:

 

post-90-0-65345400-1464742618.jpg

 

I did take a few visible pictures at infinity with the cameras just to make sure it wasn't a viewfinder focus issue.

That PK adapter has a 1mm "collar" which acts like an extension tube. I am not sure how you mount it on a Canon, but if it's a PK-EF adapter and you are using this adapter too then the problem is your M42-PK adapter. For infinity you will need a different M42-PK adapter, one without the collar, which requires a key to be able to remove it from the camera body. But be very careful with that adapter as there are horror stories with the adapter being stuck in the mount (and damaging it)... unfortunately one of those stories is my own... I'd advice to use that adapter to permanently modify a lens to PK mount (screw it on the lens with a drop of glue and then drill a small hole for the PK mount pin).

Hope it helps.

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