Service for Canon LTM lenses?

[CZeni]

Well it's happened again...right place at right time and a 50/1.4 Canon lens was mine for $20...but it doesn't focus properly. Not sure what's going on as I tried it on an M6 and on a Voigt Bessa T - yep, it's out of focus. Any suggestions for somebody who can properly collimate the lens for me?

Thanks

CZ
NC

 

[rover]

My 1.4 is just back from DAG.

Highly recommended.

 

[back alley]

20 bucks?

where what when how?

details man, details!!!

joe

 

[furcafe]

From what I understand the Canon RF lenses are pretty easy to work on. In your neck of the woods, I know that Mark Hama (http://www.markhama.com) works on Canon lenses & bodies (he's in Marrieta, GA).

Well it's happened again...right place at right time and a 50/1.4 Canon lens was mine for $20...but it doesn't focus properly. Not sure what's going on as I tried it on an M6 and on a Voigt Bessa T - yep, it's out of focus. Any suggestions for somebody who can properly collimate the lens for me?

Thanks

CZ
NC

 

[blee017]

Wow, 20 bucks?
Sherry works on Cannon RF lenses, too.

 

[CZeni]

20 bucks?

where what when how?

details man, details!!!

joe

An acquaintance from another hobby of mine.

He knew it didn't focus, it is a bit grubby (but the glass is really nice) and he just didn't want to mess with it - couldn't be bothered. Must be nice...

And for $20, why not? 🙂

And thanks for the Mark Hama and Sherri tip - I'll try them after the first of the year.

CZ
NC

 

[Sonnar Brian]

Is anything in the frame in focus, or is it all a blur? If the focus is off, ie in front or back of the point of focus: the shim needs to be replaced. The lens module comes out of the focus mount, it is held in with a retaining ring at the rear. The shim is a ring around the lens module that stands it off from the focus mount. It has to be the correct thickness for the focus to be on.

If NOTHING is in focus, either an element is in backwards, is loose, or is missing.

 

[CZeni]

Is anything in the frame in focus, or is it all a blur? If the focus is off, ie in front or back of the point of focus: the shim needs to be replaced. The lens module comes out of the focus mount, it is held in with a retaining ring at the rear. The shim is a ring around the lens module that stands it off from the focus mount. It has to be the correct thickness for the focus to be on.

If NOTHING is in focus, either an element is in backwards, is loose, or is missing.

It's the latter - it's off, but not by much. Wouldn't surprise me if an element is reversed.

 

[Sonnar Brian]

The elements not being properly seated will also cause this. One of my J-3's did this: turned out the rear group was not seated properly in its collar: it was off by about 1mm. Stopped down, it looked good. Opened up, the center was "decent" but edges were way-weird.

 

[back alley]

just to intrude a bit---

if my 135 does not focus an image at infinity then it might be because there is an improper (or no) shim fit into it?

joe

 

[Sonnar Brian]

If the RF indicates infinity, but the focus is off, the shim is the problem.

If the RF will not get to infinity, the RF pickup on the lens is off. In that case, the "Cheese-wiz" solution is to add a piece of copper tape or something else to thicken it.

I've had both happen.

 

[back alley]

'If the RF indicates infinity, but the focus is off, the shim is the problem.'

that is it.

if my photos are fuzzy (more than normal) then i understand why the lens looks unused.

joe

 

[Sonnar Brian]

I know where the shim is on a Nikkor, and have had the Canon 135 late version black lens apart.

The lens module unscrews from the mount on both of those, just like on the J-3's. A shim is acts as the standoff when screwing it in. A little bit goes a long way: 0.1mm makes a big difference. If the lens is focussing past infinity, ie nothing is in focus, the lens is too close to the film and needs a thicker shim. If it is not reaching infinity, focus is too close, the shim needs to be thinned. Usually you are best to get a new one. I have "shaved" some using sand paper, big enought to make big circular motions on the paper, and use a caliper to test thickness. You have to take it off evenly and test often.

 

[back alley]

i'll take a look at it tomorrow again when i can try to focus on something outside at a distance.
i also have a borrowed 135 that i can compare it to. (just the focusing, i won't take that one apart)

thanks brian.
joe

 

[back alley]

my borrowed lens focuses perfectly and mine does not.
it does not quite make it to infinity. so i'm thinking (from what brian said) that the shim needs to be thinner.
unfortunately, i have nothing than can reach into the rear of the longer barrel to unscrew the lens assembly. for my much shorter 35mm lens i used a small pair of needle nose pliers.

i still have to develop the film from this lens so i'm not sure what the pics will look like.
chances are i will have to send it off for repair if i want to use it though.

joe

 

[Sonnar Brian]

Are you sure that is the retaining ring for the lens module and not just the rear element? My late model Black lens just comes apart: Grab the front and unscrew it. The rear element has a retaining ring.

Can anyone answer this about the chrome lens?

 

[back alley]

i misunderstood that prior post. i'll check it out now. my lens is the black version, later model i think.

joe

 

[Sonnar Brian]

Let me know how it goes. I can post some pictures in the next day or two if you need it.

 

[Sonnar Brian]

I just took mine apart: grab the front and unscrew it. I cleaned the rear element while it was apart. It looks like a shim with a retaining ring screwed Over it. The retaining ring also has a set screw. The retaining ring acts as the stand-off when screwing the lens into the mount. I did not take this assembly apart, but it certainly keeps the retaining ring from falling out and getting lost when you unscrew the lens! Smart Move.

 

[back alley]

yes, i did the same. that brass looking ring under the silver ring - that's the shim?

so i would need a thinner ring or have to sand that ring down a bit to make it focus properly?

good luck joe!

joe