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DIY lens collimating


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I've posted a <a

href=http://host.fptoday.com/melek/zeiss/repair/collimate/collimate.html

target=_new>page on collimating lenses</a>. That is, setting infinity

focus precisely. It's fairly simple to do, and it's much more accurate

than using ground glass and a loupe while peering through the back of

the camera.<p>

 

Here's my standard test shot from a Contaflex I that was recently

overhauled. Shot on good old Kodak 200. I think I was shooting at

about f/5.6 to minimize depth of field.<p><div>00Bug6-22978384.jpg.3b1158f12123ba3d321f5ed720c1bded.jpg</div>

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I do this the same way with a Nikon F3HP & 200/4 lens for a little more magnification. A 180/2.8 would be a little brighter. I take a bare tungsten bulb and put that close to the back of the camera with the target to get lots of light.

 

I still like to double check minimum focus on ground glass after infinity collimation because some lenses get "fixed" through lens swaps and such. These kind of "fixes" can throw out the focus tracking throughout the full range.

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An excellent contribution. Do follow Mike's advice.

 

I was looking at the 50mm Sonnar and by golly I see the family resemblance to my Jupiter 8. I also notice that you removed the plug/screw that controls the aperture opening on the Yumpin Yupiters.

 

There is one final step upon reassembly. On my Jupiters the aperture ring has to be readjusted afterward, as the aperture marks usually no longer line up at the center mark on the focus scale.

 

Another point, if you have the lens disassembled this far. There is easy access to the lock screws for front element retaining ring. If the lens has dust particles between the elements, it's a great opportunity to remove them.

Best Regards - Andrew in Austin, TX
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Yes, recently read that on your website, thanks Mike.

 

The lens I'm actually servicing (and is fully taken apart with its mechanical parts soaking in Naphta and its front lens waiting for a slight repolishing) is a collapsible prewar 2/50 CZJ Sonnar, and it's shimmed with two spacers. As far as I have seen there is no collimation to do when reassembling it, am I wrong, am I right ?<div>00Bun9-22980984.JPG.7c9deac10f0195f137bb834ac0f53741.JPG</div>

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Mike,

 

One question: If I understand correctly on a prewar contax RF you adjust infinity focus by fitting spacers under the lens mount, while on the postwar cameras this adjustment is done directly on the lens?

 

I guess this is why while taking apart my IIIa a few days ago I didn't find any spacers under there....

 

This seems to be a little strange, theoretically at least, the same lens used on two different bodies could be focusing differently!

 

My Vote goes to the PreWar!

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That's correct. The prewar lenses uses foil and copper shims to set infinity focus. With any of the older lenses, it's not a bad idea to ensure that infinity focus is correct, especially if it looks like someone else has done work on the lens.
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Marco, I'm not sure I understood correctly what you wrote, but I'm afraid you made a confusion.

 

There are shims under the lens mount of the camera body - whatever the camera is (II, IIa, III, IIIa, 2A, 4, 4A, 4AM...).

 

There are also shims and coils in the prewar lenses to ensure a good collimation of the lens.

 

On the other hand, there are not shims in the postwar Sonnar, but a relief dot in the outer lens barrel that slips into the U of the lens barrel, which has to be collimated before you finish the lens reassembly.

 

To sum up, for servicing the prewar lens, just fill the lens outer barrel with the shims and coils they put in it at the factory (and you've found in it when dissassembling), and you're done (theorically).

 

So it's a mistake to say that the same lens could be well collimated for a body and not for the other. Collimation is universal and an optics and mathematics superlative concept.

 

Right the Mikes ?

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I've reset the infinity on several of my folders, and on my Reflex II TLR, with excellent results using a loupe and ground glass substitute at the film plane, but those are larger negatives and a larger image to examine; I don't doubt this is a better way for 35 mm.

 

However -- the 35 mm I most need this on (at least until I get around to a CLA for my M42 135 mm, which doesn't reach infinity) is my Olympus Pen EES-2. After cleaning the aperture to restore basic functionality, despite marking the lens barrel, I've never gotten the focus quite right; at f/11 or smaller, with ISO 400 in good light, it's pretty much okay (really looks fine at f/22), but when it opens up a bit it's pretty obviously focused beyond where I set.

 

Problem is, the shutter doesn't have a B setting; I don't know of any way to lock it open in order to set the infinity. The existing speeds of 1/200 and 1/40 just don't let me see anything. Any suggestions how to hold the shutter open with the front element in place?

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The only thing I might suggest is to select the lowes ASA/DIN setting and then hope for the slowest shutter speed possible. And then work really quickly, allowing the image to burn into your brain a bit as you twirl the lens to and fro a slight amount each time.
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This is great info to bring to the attention of the group, Mike. The last half dozen or eight cameras I've reset the inf focus on were done with this method. Worlds easier to get it right the first time than with my old way of doing things, ie: frosted glass and a loupe. The old way worked, but it often took me a number of tries to get it spot on, probably due to my middle aged eyes. Your method is nearly fool proof, (thank goodness, for my sake!).
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<i>The only thing I might suggest is to select the lowes ASA/DIN setting and then hope for the slowest shutter speed possible. And then work really quickly, allowing the image to burn into your brain a bit as you twirl the lens to and fro a slight amount each time.</i><p>

 

Mike, the EES-2 has only two shutter speeds -- 1/200, and 1/40. If the light level is too low for f/2.8 at 1/40, the red flag appears in the viewfinder and the shutter won't release (don't forget, this is a 1960s vintage auto-exposure camera). The shutter switches to a fixed 1/40 if I engage the flash aperture settings, but even at 1/40, the image doesn't "burn into my brain" and I can't turn the lens enough to notice -- and then I have to operate the film advance to cock the shutter before I can fire again.

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Donald, that's a tough one. Here's a theoretical: Remove the rear lens element. Trip the shutter at the slowest speed while lightly pressing a pin against the shutter blades. When the shutter blades open, push them open all the way with the pin or a small dowel. Insert a small collar into the lens to keep them open. Replace the rear lens element. Set focus. Remove rear lens element. Remove collar. Replace rear lens element.

 

Would this work in the real world and not in my fantasy lens collimation world? Hmmm ...

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Your method is a great step forward! I looked at a similar method that used a 35mm camera to check the image. I felt that the image was too small to be accurate. With MF, the image is huge and the accuracy is secured. I think I'm going to check my flektogon.

 

Richard

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