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Scott
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, January 24, 2005 - 09:56 am: | 
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Does anybody know the trick for adjusting the focus on a Welti 1C. Mine seems to be off, and I can't see where to make the adjustment. It's got a distance scale in meters attached to the shutter with two screws. The focus lever has a little pointer that slides past the marks on the distance scale. Mine has no rangefinder, and it's the model with the flash shoe on top of the viewfinder. It a unit-focused CZJ Tessar on a Vebur shutter. thanks. |
Winfried
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Votes: 0 (Vote!) | | Posted on Monday, January 24, 2005 - 01:22 pm: |
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I have both a Welti and a Beltica. Both came with several shutter/lens combos, and since the better lens (CZJ Tessar) was on the cheaply made Beltica I swapped it against the shutter/lens (Trioplan, not a bad three-element lens... but can't compared to a postwar CZJ Tessar) of the Welti 1c.
Both cameras had paper/cardboard shims between the shutter flange and the lens plate. I think there is no other way to adjust focus than placing/removing shims. You will have to remove the shutter from the camera by loosening the big ring nut you can see from behind.
If you still have your high school textbook on physical science you can calculate the thickness of the shims by checking the focus difference on the focus scale.
However, the Welti Ic is a great little camera. Not as pocketable as, say, a Zeiss Contina or an early Retina. But the viewfinder is much more comfortable, and the Tessar lens can easily compete with anything made in the west. |
Scott
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, January 24, 2005 - 04:13 pm: |
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Hi, thanks for the advice. I'm ashamed to say I chucked my high school textbooks long ago (but I think I still have my machinists' pocket reference book somewhere....). Got a formula for me? Suggestions for shim material?
I like using the Welti 1C, too, but all of the various linkages in the shutter make using the shutter button rather stiff. I prefer to trip the shutter by poking my finder down between the door and the door strut.
It takes a lot of force to rewind the film. I don't know where the friction is, or it's normal. When I rewind the film, it makes the frame counter count in reverse. Is there a way to disengage that while rewinding that I haven't seen? I just pull up on the advance knob to disengage the advance spindle.
Also, it takes more force to cock the shutter than on any other camera I've owned. Is it normal to be so stiff? |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 25, 2005 - 07:32 am: |
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The basic formula for optical imaging is
(1/a) - (1/b) = 1/f
a distance from lens nodal point to object
b distance from lens nodal point to image (film) plane
f (nominal) focal length
If you have to set your lens to, say, 10m instead of oo to get a sharp image on the film plane (of a very distant object) you can calculate the necessary variation of b. In this case a will change, too, but shifting the lens a few mm does not affect the (very long) distance to the object significantly. (In case of a reading of 10m, you will need an additional shim of 0.25mm thickness. When calculating don't forget to write all distances in mm since the focal length usually is given in mm - 10m object distance will be 10000mm.)
You can punch or cut shims from paper. Actually once I found a shim made from some printed paper, seems as if they used their office notes for making shims.
I don't remember it exactly but I think there was not significantly more friction than on other cameras when rewinding the Welti1c. I had a similar problem on a FED1. Reshaping the upper end of the take up spool (which has a press fit on the advance shaft) solved this problem.
I think the frame counter is designed to run backwards when rewinding. I have seen this on some other cameras, too.
It's true, the east german Vebur (and similar Tempor) shutters have rather strong springs. As long as the shutter runs fine there is no reason to fix anything. |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 25, 2005 - 02:55 pm: |
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Concerning the shutter release, yes, it used to be pretty hard on mine, too. I greased all the shafts and bearings lightly and now it works somewhat better but it still is miles away from many others much softer releases. |
Scott
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 08:08 am: |
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Thanks for the formula, but I'm afraid that whatever I'm able to work out on paper probably isn't going to help me much. I'm thinking it's gonna have to be more of a 'trial and (a lot of) error' sort of project, when I finally decide to do it. I'm kind of curious to see how difficult this will be (is that what makes me a 'tinkerer'???). Anybody know what kind of equipment they used in Dresden when they were calibrating/shimming these cameras?? Is this only a problem on folding cameras? I guess that the struts and hinges might give each individual camera unit somewhat different tolerances.
Here's what I'm going to try, and I'll let y'all know how my primitive method works: Seems to me that I oughta be able to pile on (or take away) shims while checking the focus, or rather checking the distance setting (on the camera's meter scale) at which I get a focused image. When I get a focused image, if the distance on the meter scale on the camera is more than the actual distance, then that means that the lens needs to be 'shimmed' further away from the film plane. If the distance on the scale is less than the actual distnace, then I need to remove shims. Does that make sense? Or have I got it backwards? What I'm aiming at is a test pattern on the TV screen. |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 12:13 pm: |
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I think the equipment they used in Dresden was pretty similar to the equipment all camera manufacturers used for adjusting the focus: a collimator and a focussing screen, maybe a focussed microscope.
I think the necessity for lens adjustment is rather due to tolerances of the lenses. Hardly any assembled lens has exactly the focal length engraved. A 50mm lens may have a few tenth of a millimeter tolerance (there are german and maybe international standards for that) which must be compensated by adjustment. So not just folding cameras have to be adjusted, but ANY lens on ANY camera, although most cameras do it by turning the focussing ring.
Oh yes, you have got it pretty backward... If you set a lens to shorter distances it moves away from the film plane. So if a distant (inf.) object is focussed properly while the lens is set to 10m, you had to move the lens further forward for proper focussing. To get the dial to the oo mark you have to add some shims.
I would prefer using a distant object (or one of the 'backfocussing' methods described in the article section) for setting the oo focus. Closer objects usually are harder to focus precisely. Also, due to the above mentioned tolerances in focal length markings for closer distances may be somewhat off. (I have read in an old Voigtlaender brochure about their folding cameras that they matched the focussing scale with the lens, i.e. they had several focussing scales to match with tolerance fields of the lenses... but this was back in pre-war times when they did not manufacture hundreds of lenses a day.) |
Scott
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 27, 2005 - 03:02 am: |
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Another question: I've got the rear lens element/s out, but I'm not sure what to remove now to get the shutter off of the camera. It's being held on from the back, right? Or is there something I need to remove from the front side also? I've tried to unscrew the brass-colored ring with two notches, but it's in there tight. There's no left-handed threads here, are there? |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 27, 2005 - 06:11 am: |
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If I remember it correctly you don't have to remove the rear element. All you have to unscrew is the ring around the shutter collar. Maybe it is quite tight - it is supposed to be tight since it holds the shutter to the camera. You don't have to remove anything from the front.
Shutter collars usually don't have left-handed threads. The only one I have heard of with a left-handed thread is the shutter of the late Canonet models. |
Scott
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 27, 2005 - 07:42 am: |
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before I put a lot of torque on it, I'm trying to decide which ring I ought to remove. Closer to the rear of the camera is a narrow groove (circular) that has no notches, but rather two studs down inside the groove. The ring that I assume is the collar nut (the ring with 2 notches) seems itself to be threaded on the inside. On mine, I couldn't have gotten my spanners into the notches without removing the lens element. |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 27, 2005 - 11:19 am: |
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I just had a look at my Welti1C. Yes, the groove is very narrow - similar to the Retina1 where it is also easier to remove the shutter assembly with the rear lens element removed. |
