Lens Repair

MartinCrabtree said:

If I press lightly on the front element it stops. Does that tell you something?

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Before you trash it, try tightening the beauty ring. They sometimes loosen from vibration.
I use the edge of a rubber stopper held to the ring. If it's very loose it may spin by using a pencil eraser
That's not enough for a permanent fix but it give you a hint.

flavio81 said:

Adjusting infinity stop is trivial. $250USD for each is theft.

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What annoys me is that all of the shops that will even talk to you about a 30yo film camera lens seem to only quote a one-price-fits-all type of thing for all repairs. I'm sure something has slipped and if I was a bit more confident in my camera repair skills I would try a do-it-yerself type of thing. I've resurrected a dead GIII and made a good Mamiya SD Frankencamera out of two less-than-perfect ones.

Leigh B said:

But is the problem really the lenses? Awfully odd to have two with the same issue.

Could it be that the camera is damaged, with the lens mount being bent or displaced?

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Here's the story. And I know I've posted details on here and on RFF. My problem is "soft focus" and I've done countless test rolls and test targets and test shots along a railroad track, focusing carefully on a signal light and then at infinity and comparing where the rocks and wooden ties on the tracks are in best focus.

I know I have one wonky body. Normal lens focuses just past infinity in the viewfinder but sharpest focus on film is closer than infinity.

My "good" zoom (Ozunon 28-135, also sold in the States under the Vivitar brand) is waaaayyyy off on infinity focus. Will not focus to infinity in the viewfinder.

My "other" zoom, Pentax Takumar 28-80 kind of clicks in and out of good focus. If I "exercise" it by quickly going in and out of macro mode, it "clicks in" to proper focusing. This was a local camera show find and checking That Auction Site these go for just a little more than a dime a dozen so it probably is not worth getting fixed. It may be a good test subject to try working on during a long day off sometime.

Now (to make a long story long) I recently got a MG body with another identical normal 2.0 lens. Using this body, both normal lenses focus properly both through the viewfinder and on film. The Ozunon will not focus to infinity on this body either. The 28-80 Takumar will focus to infinity if it happens to be "clicked in" to normal focus at the time.

I know I can get the K1000 CLA'd at several places for a semi-reasonable price. NBD. It's the Ozunon 28-135 that I want to get working properly again and it seems like places either don't want to work on it or want to charge three times the street price of the lens for a repair.

John Koehrer said:

No. $250.00 is nonsense. If you're getting more, there should be picture of you on the post office wall.

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Remember, both elected officials and Most Wanted appear on post office walls. Sometimes the same individual will appear both places.

The reason for the high estimate is that most lenses that don't focus properly have been damaged.
Something has shifted out of position, otherwise it would focus properly.

Actually collimating and aligning a zoom lens is a major task, requiring specialized equipment.
It's many orders of magnitude more complicated than working on a prime (non-zoom) lens.

I've never heard of an "infinity stop" on a helical-focus lens.
I've encountered those on Graphic press cameras.

- Leigh

Leigh, although long helical focus lenses are sometimes made to focus through infinity, short ones typically stop at the infinity position. A mechanical stop does this. When a helical focus lens is disassembled and reassembled incorrectly it can, doesn't have to, focus through infinity or fail to focus to infinity.

Dan Fromm said:

Leigh, although long helical focus lenses are sometimes made to focus through infinity, short ones typically stop at the infinity position.

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Hi Dan,

I'm aware of that.

Long FL lenses are subject to dimensional changes when the temperature changes.
Actually, this happens with all lenses, but only matters for ones with long focal lengths.

Long FL lenses allow the helix to move past its normal infinity position to accommodate this.

- Leigh

Yes, Leigh. Look at what you wrote in post #28 above. Are you sure that short focal length lenses in focusing helicals don't have infinity stops?

Dan Fromm said:

Are you sure that short focal length lenses in focusing helicals don't have infinity stops?

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Hi Dan,

All lenses have stops at both ends of the helix rotation.
The infinity focus "stop" that I've encountered is built into the mechanism.

The question is whether or not they're adjustable in the field.
i've worked on a fair number of lenses and never encountered same.

The total number is certainly not a statistically significant percentage of all lens models ever made. In fact, they're only from a couple of manufacturers.

- Leigh

You just haven't been working on the right lenses.
Some have a sliding stop held in place by a grub** screw, others may have an
internal ring that also uses a similar screw. I believe at least used a sliding shoe.


** Some things are just grubby

Martin Crabtee,
i am the amateur repair guy at http://www.richardhaw.com and in my experience with that type of Nikkor zoom from that era is that it is very delicate.
your problem might be caused by many different things.

infinity:

• a fuked up helicoid that was wrongly put-back.
• a debris preventing it to collapse all the way.
• wrong rear element distance.

wonky focus:

• a misaligned element
• adjustments needed

it is also annoying that some Nikkor zooms of that era exhibit this focus shift problem. I have worked on some pristine samples and they exhibit this focus shifting tendency but it should not be too much.