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03-20-2016, 04:20 PM   #1
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Old zoom/macro lens won't focus at all

Hi,

I was testing some of the old lenses that I'd acquired awhile ago for my Pentax cameras, and one of them (PLEASE don't laugh !) a "Rony 28-70mm" zoom macro lens doesn't appear to focus at all (this isn't an infinity focus problem... it doesn't focus at any distance). This is an M42 screwmount lens, and it has 4 control rings:

- aperture
- macro (has an arrow with label "Macro")
- zoom
- focus

I first tried it on my K-x using an M42-K-mount, but it wouldn't focus, whichever way I had the Macro ring turned, and at any distance.

So then, I tried it on one of my Spotmatics, and it still wouldn't focus.

When I turn the focus ring I can see the front end of the lens moving in and out (shorten or lengthen), so the focus ring seems to be moving all right, but the lens is just not focusing?

What would cause this? This is a mechanical lens and I'm only doing manual focus, so why would the lens not focus?

FYI, I also had my daughter try, as I wanted to make sure that I wasn't just seeing things, and she confirmed the same thing.

Thanks,
Jim


Last edited by ohaya; 03-20-2016 at 06:20 PM. Reason: Fix spelling of Title
03-20-2016, 04:44 PM   #2
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I'd start by taking the lens out of macro mode, since in that mode you're most likely expected to focus with your feet. If it still can't focus normally at that point, perhaps the focusing mechanism is damaged?

Adam
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03-20-2016, 04:50 PM   #3
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QuoteOriginally posted by Adam Quote
I'd start by taking the lens out of macro mode, since in that mode you're most likely expected to focus with your feet. If it still can't focus normally at that point, perhaps the focusing mechanism is damaged?
If I turn the ring to NON-Macro, it won't focus on anything, at any distance.

I just noticed something: If I put the lens into Macro mode, it WILL focus, but it will ONLY focus at ONE distance for each zoom setting.

In other words, in Macro mode, if I set the Zoom to "x" I can find one distance where it will focus. If I move back a little bit, and try to focus, I can't get it to focus. But, if I change the Zoom setting slightly, I can get it to focus for that one distance.

This lens has been sitting inside a lens case for years, inside my credenza inside my office, so it hasn't been moved for quite awhile. Is it possible that something inside the lens is "frozen"? If so, is there any way "unfreeze" it?

Thanks,
Jim
03-20-2016, 04:55 PM   #4
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QuoteOriginally posted by ohaya Quote
This lens has been sitting inside a lens case for years, inside my credenza inside my office, so it hasn't been moved for quite awhile. Is it possible that something inside the lens is "frozen"? If so, is there any way "unfreeze" it?
This happened to me with the Pentax 35-105mm. The focusing ring was extremely stiff. Using the lens brought things back to normal, but it did take a few days, and the focus always worked properly despite the stiffness.

To me it sounds like something inside your lens might be damaged, though I've never handled that particular lens.


Adam
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03-20-2016, 04:59 PM   #5
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QuoteOriginally posted by Adam Quote
This happened to me with the Pentax 35-105mm. The focusing ring was extremely stiff. Using the lens brought things back to normal, but it did take a few days, and the focus always worked properly despite the stiffness.

To me it sounds like something inside your lens might be damaged, though I've never handled that particular lens.
In my case, for this lens, the focus ring isn't stiff at all. It moves normally, at least to me. But the lens just isn't focusing ...

Jim
03-20-2016, 05:09 PM   #6
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Do you see any change in the viewfinder image as the lens element moves in and out?
03-20-2016, 05:15 PM   #7
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QuoteOriginally posted by Quartermaster James Quote
Do you see any change in the viewfinder image as the lens element moves in and out?
No, not at all. Not that either I or my daughter (who has better eyes) could tell.

Here's some pics of the lens:





And here're 2 where I moved the focus ring between the extremities (you can see the front section of the lens move forward in the 2nd pic below:





I don't "get" this. Like I said this is a simple manual lens, and from the last 2 pics above, you can see the front lens presumably moving when the focus ring is turned, and yet the lens won't focus.

And, what about what I described with Macro mode? Why is the zoom ring able to kind of/sort of get the lens focused in that case?

EDIT: I've been googling and found this thread:

https://www.ephotozine.com/forums/topic/help--my-lens-won-t-focus--94309

Maybe I ought to disassemble and re-assemble the lens? I'm not quite sure I know how to do that, but I do have some tools like a spanner wrench and small screwdrivers?

Last edited by ohaya; 03-20-2016 at 05:21 PM. Reason: Add more
03-20-2016, 05:33 PM   #8
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I'm wondering about those two holes in the nameplate ring. Do they look factory drilled, or a bit more rough as if
someone else has drilled into the lens. It could be someone else has already opened the lens and did a poor
job of reassembly. Could be a misaligned/reversed/missing lens element.

03-20-2016, 05:41 PM   #9
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I'm wondering if this might be a T mount lens. Does it screw all the way into the threads as it should, or does it stop at about 1 turn?

If it's a T mount, it's the same diameter, 42mm, but different threads, and it also has to be placed about 5/16 inch further from the focal plane of the sensor than a M42 lens. I only have 1, a Lentar 135mm, and I have the T mount adapter that works with it, but if I try to use it as M42, which I tried before I found out it was T mount, it does the same thing. Won't focus, but it won't screw in all the way either.
03-20-2016, 05:43 PM   #10
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QuoteOriginally posted by tvdtvdtvd Quote
I'm wondering about those two holes in the nameplate ring. Do they look factory drilled, or a bit more rough as if
someone else has drilled into the lens. It could be someone else has already opened the lens and did a poor
job of reassembly. Could be a misaligned/reversed/missing lens element.

I was looking at those also, as I thought about how I might disassemble the lens ... but, I don't know the answer to your question. I'm pretty sure I bought this lens as part of my first "LBA", like 15+ years ago, probably from Ebay (yes, it was around back then), and I'm pretty sure it worked.

BTW, I just noticed something: If I put the lens in non-macro, and the zoom to "70", the lens DOES seem to be focussing! Moving zoom to 28, the lens still does not focus, or at least it doesn't seem to focus (then again, the lens may be so lousy that it's hard to tell if it's focused or not?).

---------- Post added 03-20-16 at 06:12 PM ----------

QuoteOriginally posted by Paleo Pete Quote
I'm wondering if this might be a T mount lens. Does it screw all the way into the threads as it should, or does it stop at about 1 turn?

If it's a T mount, it's the same diameter, 42mm, but different threads, and it also has to be placed about 5/16 inch further from the focal plane of the sensor than a M42 lens. I only have 1, a Lentar 135mm, and I have the T mount adapter that works with it, but if I try to use it as M42, which I tried before I found out it was T mount, it does the same thing. Won't focus, but it won't screw in all the way either.

Hi,

That was ALMOST brilliant !!

I happen to have a T-PK adapter, because I have a lens (a Soligor 28mm) that is a T-mount lens. So when I saw your post, i got all excited, and I put the "Rony" lens on the T-PK adapter and tried it on my K-x and... it wouldn't focus at all, even at zoom set to 70 ...

Sigh ...

Can I summarize at this point... maybe something will "hit":

1) If I put lens into macro mode, it will focus for a specific distance for a specific zoom setting, but if I change distance (but leave zoom alone) it won't focus.

2) It will focus in non-macro mode if zoom is set to 70.

3) In all other cases, it doesn't seem to be able focus and image doesn't change when I move the focus ring.

4) It doesn't seem like it's a T-mount lens.

Does anyone have any other ideas?

Does anyone know how difficult it is to disassemble a lens like this? Also, if I do disassemble it, what do I look for?

Thanks,
Jim

EDIT: I think that I may've figured out what's going on... but this doesn't make sense, to me...

Remember that this is a legacy lens, i.e., originally designed for 35mm film.

The lens shows the minimum distance on the focus scale at 7 feet, but I'm conjecturing that when used with a K-x, that the distances are increased.

In other words, I think that the actual minimum focus distance for this lens, when used with a K-x is probably way, way more than 7' and when i was testing earlier, I was too close to whatever I was testing against, which is why nothing ever seemed to be in focus. I just tested all the way across my house and was able to focus with the zoom set to just under 50.

The thing that doesn't make sense to me is that the minimum focus distance seems to be larger if the zoom is set to a lower number.

Shouldn't it be the opposite of that? Shouldn't a longer lens have a longer minimum focus distance?

Why is this lens behaving the opposite way?

Last edited by ohaya; 03-20-2016 at 07:03 PM. Reason: Add info
03-20-2016, 06:59 PM   #11
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What is this? Is it a threaded hole missing a screw?
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03-20-2016, 07:17 PM   #12
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QuoteOriginally posted by Quartermaster James Quote
What is this? Is it a threaded hole missing a screw?
Hi,

Sharp eyes ! But, those are holes that the adapter makers counter-sink set screws into so that you can loosen the set screws and turn the front part of the adapter so that the numbers on the aperture ring, etc. end up "on top". In my case, I haven't messed with those yet because I'm still testing with the adapter.

Plus, you would kind of do that adjustment for every lens, since their numbers would end up in different places.

Jim
03-20-2016, 07:25 PM   #13
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Was it ever a working lens? You say it's been inside a credenza in your office for some time, was it working when you'd acquired the lens?
03-20-2016, 07:38 PM   #14
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QuoteOriginally posted by excanonfd Quote
Was it ever a working lens? You say it's been inside a credenza in your office for some time, was it working when you'd acquired the lens?

Actually, I got so long ago, that I don't know for 100% sure now , but I'm *guessing* that I must've used it, or at least tested it, back then....
03-20-2016, 07:43 PM   #15
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Does anything rattle when you shake it?

---------- Post added Mar 20th, 2016 at 06:46 PM ----------

QuoteOriginally posted by ohaya Quote

The lens shows the minimum distance on the focus scale at 7 feet, but I'm conjecturing that when used with a K-x, that the distances are increased.
I don't believe this is correct. At least, I have never encountered this using legacy glass on digital bodies, nor have I seen it previously mentioned in discussion of same.
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