TLR focus problem

[E. von Hoegh]

Ideally, the viewing lens will be precisely the same focal length as the taking lens. When this condition obtains, you can set the taking lens to be perfectly focussed at infinity, as seen on a GG at the filmplane, then shim the screen/ adjust the viewing lens so it is sharp and you're finished.
If the viewing lens and taking lens have slightly different FLs, you'll have to go back and forth until they track adequately across the focussing range. If the taking lens has focus shift as you close down the aperture, do the adjustment at the aperture you most use.

 

[Tom1956]

Ideally, the viewing lens will be precisely the same focal length as the taking lens. When this condition obtains, you can set the taking lens to be perfectly focussed at infinity, as seen on a GG at the filmplane, then shim the screen/ adjust the viewing lens so it is sharp and you're finished.
If the viewing lens and taking lens have slightly different FLs, you'll have to go back and forth until they track adequately across the focussing range. If the taking lens has focus shift as you close down the aperture, do the adjustment at the aperture you most use.

+1

 

[stevebarry]

Got it. Both lenses are the same focal length 75mm 3.5. The ground glass on the film rails is sharp at infinity.

Before I go adjusting anything, and potentially making the problem worse - I am just trying to be sure that :

A) the mirror would not be causing the problem (mirror replaced with a thicker one, or its not seated down in the clip)
B) if there is any combination of ways the original focus screen and fresnel could be installed that are causing the problem (someone took it apart to clean and put it back wrong, etc.)

if there is a solution that would not have me shimming the viewing hood/screen or worse tearing the camera apart to somehow adjust the viewing lens, that would be great.

 

[Tom1956]

Yeah, make sure the mirror wasn't flipped over to the wrong side. On a Rollei, it's coated side up. The groundglass/fresnel sandwich it Groundglass on top (obviously), dull side down. Fresnel is beneath it, etched side up. From that point, since your film plane is good to go, then adjust the taking lens to match. This is how I'd do it. I don't much care for shimming.

 

[E. von Hoegh]

Got it. Both lenses are the same focal length 75mm 3.5. The ground glass on the film rails is sharp at infinity.

Before I go adjusting anything, and potentially making the problem worse - I am just trying to be sure that :

A) the mirror would not be causing the problem (mirror replaced with a thicker one, or its not seated down in the clip)
B) if there is any combination of ways the original focus screen and fresnel could be installed that are causing the problem (someone took it apart to clean and put it back wrong, etc.)

if there is a solution that would not have me shimming the viewing hood/screen or worse tearing the camera apart to somehow adjust the viewing lens, that would be great.

Lenses are marked with a nominal focal length. As I said, "precisely the same focal length" - the exact focal length may be as much as 5% different from the nominal focal length. Ideally, the lenses would be individually tested and paired with taking lenses of precisely the same focal length.

Something else to keep in mind - is that it's probably a safe assumption that the camera was right when it left the factory - what changed?

 

[Tom1956]

I USED to be of the school of thought that things were right when they left the factory. And they usually are. But truthfully, Japanese manufacture in the early 60's left something to be desired. Take the Rapid-Omega 100 and 200--great cameras. Then look at an early Koni-Omega, a clattering hunk of junk sheet metal in comparison. Maybe I'm getting old and and a bit cynical. I've worked on enough Hasselblads to see that they weren't all they're cracked up to be.

 

[E. von Hoegh]

I USED to be of the school of thought that things were right when they left the factory. And they usually are. But truthfully, Japanese manufacture in the early 60's left something to be desired. Take the Rapid-Omega 100 and 200--great cameras. Then look at an early Koni-Omega, a clattering hunk of junk sheet metal in comparison. Maybe I'm getting old and and a bit cynical. I've worked on enough Hasselblads to see that they weren't all they're cracked up to be.

As I said, "probably a safe assumption".

 

[E. von Hoegh]

Well, one thing's for sure--you already found one problem that must be corrected before proceeding. It's not always just one problem; it could be several working additively. I'm not a fan of groundglass shimming. I still prefer seeing if the groundglass had been tampered with, and barring that, proceeding to turning the viewing lens in its setting. How do you know you are not just now getting sensitive to a problem that was there from the factory? Just yesterday I threw a Nikkormat FTn in the garbage because the factory failed to tighten a pentaprism hold-down screw, and thart screw eventually backed itself out and fell down in the copal shutter and ruined it. My forensic disassembly method convinced me I was the first person that ever opened the camera up. It was a virgin.

High frequency vibrations can cause a screw to back out in an amazingly short period of time. Think of it, screws don't unscrew themselves - tension doesn't do it, so it has to be vibration. Where's a common source of HF vibration? Jet aircraft engines. This is also why screws used to mount sights and 'scopes on guns are very fine thread 6x48 and 8x40 - the barrel vibrates quite a bit when the bullet goes down the rifled bore. Since a screw is just a cylindrical wedge, it follows that the shallower the slope of the wedge, the less vibration will affect it. Screws used in cameras aren't particularly fine pitch.

 

[stevebarry]

Yes, I am assuming it was right when it left the factory, at least for now. Which is why I am trying to figure out what has changed and causing the focus to be out on the focus screen before I go tinkering.

Without being able to ascertain the mirror size or position when leaving the factory, and also not understanding how sliding the mirror down to seat into the bottom clip would effect the focus - it seems to me, sliding it up or down would not bring it closer or further form either the lens or the screen, which as I understand it would be the only way it would affect the focus. So I am going to leave the mirror be for now.

From what I have been able to see from different sources around the net, the screen seems factory equipment on a model L.

There is nothing jammed, dented, or otherwise damaged. Everything seems in good shape, everything is tight, nothing seems out of line, etc.

So I am left thinking either someone took the focus screen out to clean it and put it back wrong, or had a different Fresnel put on, or the mirror is causing the problem. I will take the focus screen apart tonight.

BTW - I did attempt to shim the screen and a playing card thickness was too much. So.

 

[E. von Hoegh]

Yes, I am assuming it was right when it left the factory, at least for now. Which is why I am trying to figure out what has changed and causing the focus to be out on the focus screen before I go tinkering.

Without being able to ascertain the mirror size or position when leaving the factory, and also not understanding how sliding the mirror down to seat into the bottom clip would effect the focus - it seems to me, sliding it up or down would not bring it closer or further form either the lens or the screen, which as I understand it would be the only way it would affect the focus. So I am going to leave the mirror be for now.

From what I have been able to see from different sources around the net, the screen seems factory equipment on a model L.

There is nothing jammed, dented, or otherwise damaged. Everything seems in good shape, everything is tight, nothing seems out of line, etc.

So I am left thinking either someone took the focus screen out to clean it and put it back wrong, or had a different Fresnel put on, or the mirror is causing the problem. I will take the focus screen apart tonight.

BTW - I did attempt to shim the screen and a playing card thickness was too much. So.

Cigarette papers, onionskin, copier paper, writing paper; from thin to thick - all are thinner than a playing card which is probably around .008-.012".

The front of the camera could have recieved a blow - from a soft odject there'd be no mark, but a slight misalignment is all it takes.

 

[stevebarry]

No doubt I was going to try different thickness papers. I was just saying, the needed adjustment is very slight. Could something this slight be from an upside down Fresnel? probably hard to say.

 

[Tom1956]

I'd slip the mirror down under the clip, like it's supposed to be. Obviously that's what it's for. And having the mirror dangling could well be your problem in the first place. It's just too obvious to ignore. WHY is the clip and backstop there? Just too obvious. No, it won't change the plane, but it WILL secure the mirror. It's too much like a Rollei in its design, and Rollei has a bottom backstop and spring to hold the bottom of the mirror in place. It's evident somebody has had that camera open before. And while you're at it, see if THEY didn't flip the mirror over, like a boob, which could very well be the cause of your problems. But it obviously belongs in the bottom clip.

 

[stevebarry]

The mirror has a frosted side and a regular mirror side. The regular side was pointed out... So I just put it back and slid it down into the bottom clip. There was a little clip behind the mirror the mirror was not seated in which was holding the mirror out-and I thought that might fix the problem. No difference in focus on the screen. So I guess I am left shimming the hood. I may try to get another mirror in hopes that someone has replaced the mirror with the wrong thickness mirror.

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[Tom1956]

Sounds like it's the correct mirror. Rollei mirrors are coated on the front and the back looks frosted. I believe you have the right mirror. You can do the shimming method if you wish. As for me I prefer getting the front cover off and doing it the correct way.

 

[stevebarry]

what is the red needle on the focus lever for? is it a coincidence that infinity comes into focus on the screen when the red needle is over the infinity mark?

 

[Tom1956]

That I cannot answer. Check the owner's manual, probably available on Butkus. I did not realize that this camera used a linear focus knob--never saw one before.

 

[stevebarry]

Red mark is some sort of zone focusing /infrared mark.

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[stevebarry]

Maybe it was adjusted to be infrared only rig? I know nothing about infrared photography. But would how the camera is now (intentional or not) be right for infrared film - able to be focused normally on the screen? Or would this be backwards?

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[Tom1956]

No, it's just out of adjustment. Take off the front panel and adjust the viewing lens for infinity. It's that simple.

 

[stevebarry]

So my logic is fuzzy?

When the focus screen is sharp at infinity the red infrared mark is on infinity .

The mark is fixed making it constant through the range of focus? So the difference should translate to all distances?

What am I missing?

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[Tom1956]

Yes the mark maintains for all IR distances. Look at a 35mm camera lens. Don't ask it to make sense, because it doesn't to me either. But you're just trying to get your VL and TL to jive for regular film right now.

 

[Zathras]

I found A service manual. On the last page it talks about adjusting the taking/viewing lens.

Dead Link Removed

If I am not mistaken I need to remove the leather covering to get to this stuff? I may be out of my league here. The camera is mint condition. May be worth me shipping somewhere.

If you send it off for repair, Karl Bryan in Beaverton, OR is THE MAN as far as Autocords are concerned. Fast turnaround, very reasonable prices and excellent work. He worked on my Autocord last year and it came back looking and working like a brand new camera.

 

[E. von Hoegh]

what is the red needle on the focus lever for? is it a coincidence that infinity comes into focus on the screen when the red needle is over the infinity mark?

View attachment 71092

It's the index used for focussing when infrared film is used. If it indicates focus for visible light, something is wrong... Which index lines up where when you are verifying focus with groundglass at the filmplane?

 

[stevebarry]

That is what I'm saying infinity is sharp on focus screen when red IR mark on lever is at infinity. Infinity on film plane sharp on regular mark. So loaded with the right IR film... theoretically I should be able to use focus screen to focus right?

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[E. von Hoegh]

That is what I'm saying infinity is sharp on focus screen when red IR mark on lever is at infinity. Infinity on film plane sharp on regular mark. So loaded with the right IR film... theoretically I should be able to use focus screen to focus right?

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Wrong. Infinity must be sharp on the screen and at the filmplane for visible light when the regular mark is at infinity.
The focus on the screen must coincide with the focus at the filmplane. This is the entire point of a TLR. The way the camera is now, you will not get proper focus for visble or IR light.