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Retina 1 focus problem.
Old 02-07-2011   #1
Grytpype
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Retina 1 focus problem.

O.K. it's not a Retina rangefinder, but I think the basic focusing principle is the same.

My Type 149 has the Schneider Xenar f3.5 lens. It hits the infinity stop before it reaches correct focus at infinity, and at shorter distances it focuses about 1/8" further up the scale than it should (i.e. a genuine 3 metres focuses at 4 metres on the scale).

It has a proper focusing helical like other Retinas, so the whole lens/shutter moves - correction for infinity focus is not just a matter of re-positioning the focus-ring as it would be on a front-cell focusing camera. Also, I'm sure that if someone had dismantled the helical and re-assembled it wrongly, the error would be much greater than this.

Does anyone know how infinity focus should be set on these cameras?

I have a bad feeling that I already know the answer, namely that the lens/shutter unit will need to be removed from the focus-mount, and shimming behind it reduced. This looks like a major operation, because what I think is the retaining ring is very inaccessible and will need a special tool making. Then it would need repeated assembly/disassembly to get the shims right (removing the rear element each time).

It would be quite easy to make the necessary correction when taking pictures, so I plan to put some film through to check the bellows before I do anything, but the error will irritate the heck out of me, so I would like to be able to set it right eventually!

Steve.
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Old 02-08-2011   #2
Mr_Flibble
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Instead of testing with film, you could try with a ground glass over the film plane. I've had some success with a bit of clear plastic cut from a CD jewel case and some mat scotch tape over it.
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Old 02-08-2011   #3
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I use an SLR focusing screen held to the film-rails with elastic bands to check focus.

The testing with film idea was just to check that the bellows are OK - to make sure it is worth the trouble of getting the focus right!
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Old 02-08-2011   #4
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You can check the bellows with a flashlight in a dark room. Retina bellows are of excellent quality, so they seldom have holes.

Chris Sherlock has information about the focus mechanism of the Ia and IIa, but check with him if the type 149 works the same before doing anything.

http://homepages.ihug.co.nz/~Srawhiti/
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Old 02-08-2011   #5
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Thanks, JPD. I'd had a look at Chris Sherlock's site but missed the page on the 1a focus-mount strip. It certainly looks to be basically the same as the Retina 1. There's no mention of shims, but maybe the focus was set up at the factory by selecting the plate that screws on the front of the inner helical from a number of them with different thicknesses.

In this case it's not easy to see how the focus could be wrong, though I have some ideas on ways it could have been mis-assembled. The focus on this camera is nice and smooth, so it's likely it has been stripped down at least once in its 70 plus years' life!
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Old 02-08-2011   #6
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Quote:
Originally Posted by Grytpype View Post
Thanks, JPD. I'd had a look at Chris Sherlock's site but missed the page on the 1a focus-mount strip. It certainly looks to be basically the same as the Retina 1. There's no mention of shims, but maybe the focus was set up at the factory by selecting the plate that screws on the front of the inner helical from a number of them with different thicknesses.
There's no need for shims. I adjusted the focus on a Retina IB a couple of years ago. I can't remember exactly how I did it, though. but it was easier than I thought.

It has something to do with how the helical is positioned in relation to the shutter and focus ring. That's why you want to mark it like this:

http://homepages.ihug.co.nz/%7ESrawhiti/ret1afocus5.jpg

I remember holding the loose shutter/lens assembly in it's place, focusing the lens correctly at infinity on a groundglass in the film plane, made a mark like above and then set the focus scale back on infinity.

I made the "ground glass" exactly as Mr_Flibble did above. Matt tape on a piece of clear plastic from a CD case.
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Old 02-08-2011   #7
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It begins to make sense! When I first read Chris Sherlock's dismantling description I thought the 4 screws fixing the focus-ring to the outer helical held it directly. But from your post, JPD, and Chris Sherlock's phrase "if the focus ring is still firmly attached", I can see now that they clamp the focus-ring to the helical in some way, so that the relative position of the helical can be adjusted.

I'll probably be able to set about making a tool for that retaining ring later today. Thanks for the help, everyone!
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Old 02-09-2011   #8
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Good luck, and please take pictures of how the camera looks with the shutter off.
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Old 02-10-2011   #9
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As expected the Retina 1 helical adjustment turns out to be just like the 1a described by Chris Sherlock. The first picture attached shows it as it was when I had taken off the shutter unit. The 4 screws circled are the ones you slacken or remove to adjust the position of the focus-ring relative to the outer helical. At about "8 o'clock" on the image you can see a couple of alignment marks (arrowed) which were obviously applied at the factory. I re-aligned these, and lo-and-behold, the focus scale was accurate again! It checks OK at infinity, 4m, and 1m. I cleaned and greased the helical as well.

The second picture shows the camera. It's reasonably tidy apart from a sizeable chunk of covering missing from the door. These are really wonderful cameras: compact and beautifully made.
Attached Images
File Type: jpg retina_1_helical.jpg (71.8 KB, 21 views)
File Type: jpg retina_1_type_149.jpg (52.7 KB, 17 views)
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Old 02-10-2011   #10
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Great! Always nice to see cameras fixed and ready for use. I'm saving the pic of the helical mechanism, if you don't mind.
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