Adjusting the Industar-61L/D for the Leica

Sonnar Brian

Sonnar Brian

Product of the Fifties
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The I-61L/D is a Tessar formula lens made with low dispersion glass. Sharp and higher contrast. Also inexpensive.

The optical qualities are excellent, but it is not unusual to find one that requires adjustment. This one: we are going to adjust the focus to match the distance scale, and then build up the RF cam so that the RF of the camera agrees with the distance scale as well.

At start, the RF cam is off and the actual focus is off. The RF cam shows 7m for a 5m target, and the actual focus is just over 4.

The distance is off should be 5m for the test object that I was using,

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The Shim is off for the Leica, needs to be built up.

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Remove the Light Baffle, just like on the I-50 that was the subject of another project.

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The optics module is held in by this retaining ring and one set screw.

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Remove the retaining ring with the spanner,

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And remove the correct retaining screw. They kind of look alike, the one you want is usually in a little deeper.

It's the really long one! It's typically near the one nearest infinity mark. 1 of 3 screws that look a lot alike, and you have to pick the correct one. Just like Let's Make a Deal.

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With the retaining screw out, the optics module comes out easily. This one is going back into the LTM mount, and needs to be shimmed. This one needs about 0.1mm so that the distance scale lines up with the actual focus.

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I started with some Shimming material, cut some rough shapes. Because of the retaining screw, I use split shims. Pieces lined up on each side of the optics module. Press the metal into position to get an imprint, and then cut it so it fits into the ledge.

When re-assembling, you need to make sure the shims are in position, and the optics module holds them in place as you tighten the retaining ring. On this one, I put the retaining screw in first to hold it down. Then, tightened the retaining ring. After that, I took the set screw out, finished tightening the ring, tapped a new hole for the set screw, and put it back in.

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Focus is now close to the actual measured distance.
 
I could have shimmed the optics to match the RF cam, and let the distance scale error stay. BUT- that meant not being able to focus to infinity. The RF cam also needs to be "shimmed". I used copper tape. Again, cut a rough shape and press it onto the Cam to get an imprint. Cut a strip of tape. On this one, I used a very small amount of super-glue on the Cam and pressed the copper tape onto it. I used a metal pin to place the glue. Holds better than the copper tape alone.

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With the strip of copper tape in place, very close agreement with the distance scale and actual focus. A little room for infinity focus on this one. At F2.8, plenty close.

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This is interesting, as I happen to have a few unused I61's ! I suppose one could try producing a focus-test tube at the local craft workshop, but a possible alternative would be a carefully measured scrap ltm body, with some sort of screen bodged on to the film guide-rails - or the lens could be set up for one particular body, so without such accurate measuring of the mount-to-film distance. My main question is what do you find the best sort of image for checking this sort of thing ? Is it formed on a ground-glass, or is it an aerial image, like in a grain-focusser ?

(And of course, please keep us informed with your interesting posts!)
 
The viewer I use is ground glass. An SLR focus screen is a good choice for a homemade TTL viewer. I also have a Canon 7 with "T" setting to leave the shutter open. I use it with an exposed film strip and tape over it. Kim Coxon uses a Pentax SLR focus screen at the film gate for focus.
 
Using a non-functional FSU camera could take the place of my TTL viewer. The "Finger" used for the RF pickup will hang up on some lenses with thin RF cams, such as the 5cm F1.5 Summarit. It could be taken off. I picked up some parts Fed 2's for $5 each, the RF trim works perfectly on a Canon RF. Removable back, tripod mount, take out the shutter and put ground glass in the film gate. Shim the mount using a known-good, fast lens.

Finding a Canon with hinged back would be nice, get RF and TTL all at once. Just have to find one with a bad shutter for cheap.
 
It goes against the grain to do this because a lot of dealers sell these off cheaply as they've no idea what they are...

Periflex made a camera that was focused with a little push-down periscope. For macro work they sold a gadget that was used behind the extension tubes or bellows as a substitute for the camera and which had a ground glass screen on it. Only it was plastic & not ground glass imo.

It looked like this; with the obligatory FED lens.
914844700_PCtZf-L.jpg

As you can see the mount was offset and there's a screw to allow rotation. Here it is upside down to show the flat for the tripod bush and the lens in place:

914844715_4W6J9-L.jpg

And here it is on a tripod:
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This next one is not the best photograph I've taken but ought to show the rear of it and the screen etc:
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Lastly I've shown the box it came in.
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What's interesting - apart from the price - is that the word "Periflex" has been added with a separate stamp and suggests it was made for other cameras and lenses.

The price was £2-8-2d or £2-41 when decimalised. Purchase tax was 6/8d or £0-33 and may or may not have been included but was paid on the wholesale price and was probably 25% or 27½% depending on what financial crisis was gripping the Govt of the day. And "N/X" was probably a code for the seller's staff about the cost price or discounts allowed.

Anyway, back to the plot, these gadgets are very useful with a magnifier for checking lenses. The target I use for nearby is one of those low energy bulbs with a "U" shaped tube. Rotate the bulb to double check the focus...

Regards, David

PS As people manufacture light seal kits, I'm surprised no one makes shim kits for these lenses.
 
Thankyou for posting!

And this reminds me that I need to do a "Tools Thread". Summer is my "busy doing other stuff" time. But I will start this one soon, and would be a great place for this item.
 
Pictures are long gone, that project was over 10 years ago.







The construction is the same as the Industar-26M. Remove the light baffle at the rear of the I-61, take off the retaining ring that holds the barrel in the focus mount. Take out the screw that holds the barrel in place. I've used foil for shims, can also use paper.



Been very busy with work. When I get time, will get up a CLA for the I-26, same construction as I-61. The machining of the I-26 mount is much nicer. The I-61 is sharper.

I ended up converting the I-61L/D for use on the Nikon.




Then sold it...
 
Brian, would the later black bodied I 61 l/d lenses.. say from the early 1990s dis-assemble the same way as that silver one in your photos?
 
Yes- the construction is very-very close. Set screws holding in the focus ring and the DOF/Focus index ring. I improved the flare in the I-26M by putting the baffle from an I-61L/D into it. It's sitting on a 1952 Fed 1 now.







I bought 5 of them "need-work" for $45, made 3 good ones out of them, sold two of those, have two focus mounts for projects.
And have one that is perfect now, made in 1957.



I was hoping to transplant the barrel from the I-61L/D to the I-26M, the focus mount is that much nicer. Did not work.

I-26M, wide-open on the M9.



I found the I-61L/D that was given to me in return for doing a CLA several years ago...Construction is near identical. I used Vacuum pump grease for the I-61L/D, so focus is not as light as the I-26M.
 
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