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  1. #1

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    Vivitar 220/SL focus adjustment

    Hi,

    I just grew my old 35mm collection with a Vivitar 220/SL. The camera needs the typical cleaning and going through but was otherwise in excellent condition. I did notice fairly quickly that it would not focus to infinity. As I looked at how this camera is made, the lens mount to film plane is not adjustable. As I was cleaning old foam from the top of the focus screen I noticed ( took a while ) that the focus screen distance is adjustable ( as well as tilt ). It looked like someone did some work before and just tightened the screws that set the screen distance. No big deal, I would have probably done the same thing not knowing this design. Now the issue is getting it set right. I have another 220/SL body I bought for parts, but the focusing seems to be OK ( not previously messed with... I think ). My thought is to use the parts body on a bench and focus on a piece of graph paper fairly close in ( near minimum focus distance ) with the lens wide open. Then focus as critically as I can. Mount the same lens on the good body, set it in the same place with the lens set at the previous focus and use the screen adjustment screws to bring the image into focus. The graph paper should help me make sure the screen is also square with the focal plane. I'm sure I can come up with a way to make sure the bodies are set exactly in the same spot.

    Might also tweak the meter to use a 1.55V silver battery while I'm in there. There are some pots, need to try and find a service manual so I can see what the circuit is. Alternately, I can do the diode drop mod which seems to work very well on my OM-1s

    Any thoughts on a better way?

    Thanks

    Joel

  2. #2

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    Quote Originally Posted by Joel_L View Post
    Hi,

    I just grew my old 35mm collection with a Vivitar 220/SL. The camera needs the typical cleaning and going through but was otherwise in excellent condition. I did notice fairly quickly that it would not focus to infinity. As I looked at how this camera is made, the lens mount to film plane is not adjustable. As I was cleaning old foam from the top of the focus screen I noticed ( took a while ) that the focus screen distance is adjustable ( as well as tilt ). It looked like someone did some work before and just tightened the screws that set the screen distance. No big deal, I would have probably done the same thing not knowing this design. Now the issue is getting it set right. I have another 220/SL body I bought for parts, but the focusing seems to be OK ( not previously messed with... I think ). My thought is to use the parts body on a bench and focus on a piece of graph paper fairly close in ( near minimum focus distance ) with the lens wide open. Then focus as critically as I can. Mount the same lens on the good body, set it in the same place with the lens set at the previous focus and use the screen adjustment screws to bring the image into focus. The graph paper should help me make sure the screen is also square with the focal plane. I'm sure I can come up with a way to make sure the bodies are set exactly in the same spot.

    Might also tweak the meter to use a 1.55V silver battery while I'm in there. There are some pots, need to try and find a service manual so I can see what the circuit is. Alternately, I can do the diode drop mod which seems to work very well on my OM-1s

    Any thoughts on a better way?

    Thanks

    Joel
    Wow... that's an interesting method...


    The way to set the focus screen is to put the camera on a tripod, with a piece of groundglass at the film plane. Focus the lens, on the filmplane (shutter open!) on an object at infinity - that is, a mile or so away. Then, without touching anything else, close the shutter and adjust the viewfinder screen until it's focus coincides with the focus at the filmplane. Double and triple check before you button it up.

  3. #3

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    So, the reason I was thinking close in is DOF is much narrower. At far distances, once you are past infinity, all is good ( now maybe moving the screen does pass through a sweet spot that is obvious ). The second issue I see is how do I make sure the screen is square with the focal plane? I will give this some thought ( might work to start square ( adjustment agoinst the stops then turn each screw the same ), I like the idea of having a direct view of what I'm doing on the actual camera I'm trying to adjust.

    Thanks

    Joel


    Quote Originally Posted by E. von Hoegh View Post
    Wow... that's an interesting method...


    The way to set the focus screen is to put the camera on a tripod, with a piece of groundglass at the film plane. Focus the lens, on the filmplane (shutter open!) on an object at infinity - that is, a mile or so away. Then, without touching anything else, close the shutter and adjust the viewfinder screen until it's focus coincides with the focus at the filmplane. Double and triple check before you button it up.

  4. #4

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    I did notice fairly quickly that it would not focus to infinity. As I looked at how this camera is made, the lens mount to film plane is not adjustable.
    You probably mean the lens will not focus to infinity on the groundglass. And probably it had proper infinity focus on the film. SO it's better that you could not adjust the lens distance. Now, the groundglass mis-focus can have two causes: (a) the groundglass position; (b) the reflex mirror position. Better make sure you adjust the one that is mis-aligned; although in principle you can compensate one with the other, except for side effects on frame alignment.

    From my experience, the best (most accurate) method has been described by Rick Oleson:
    - Open the back of the camera to let some light in
    - place a known good reflex camera (preferably with a split-prism at the center of the ground glass) close in front, staring into the lens of the camera under test.
    - With both cameras focused at infinity, the ground glass of the camera under test should apear to be in focus. This checks for infinity focus on the ground glass.
    - Similar method can be used to check proper infinity focus in the film plane; just place a plane object (a piece of ground glass, or a piece of "magic" adhesive tape) precisely in the film plane (reference: film guides), open the shutter of the camera under test (B setting, cable release lock), and check whether you see in the known good camera the film plane (of the camera under test) to be in focus.

    Good luck
    Last edited by bernard_L; 04-17-2013 at 11:09 AM. Click to view previous post history.

  5. #5

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    Quote Originally Posted by Joel_L View Post
    So, the reason I was thinking close in is DOF is much narrower. At far distances, once you are past infinity, all is good ( now maybe moving the screen does pass through a sweet spot that is obvious ). The second issue I see is how do I make sure the screen is square with the focal plane? I will give this some thought ( might work to start square ( adjustment agoinst the stops then turn each screw the same ), I like the idea of having a direct view of what I'm doing on the actual camera I'm trying to adjust.

    Thanks

    Joel
    Close in does not verify infinity focus. You make sure the screen is square with the focal plane by placing the screen on the film rails. Good luck.

  6. #6

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    Quote Originally Posted by bernard_L View Post
    You probably mean the lens will not focus to infinity on the groundglass. And probably it had proper infinity focus on the film. SO it's better that you could not adjust the lens distance. Now, the groundglass mis-focus can have two causes: (a) the groundglass position; (b) the reflex mirror position. Better make sure you adjust the one that is mis-aligned; although in principle you can compensate one with the other, except for side effects on frame alignment.

    Good luck
    Why I suggested the method I did. If this camera had a 100% viewfinder, frame alignment would be critical; it doesn't, so it isn't. Although it would be a good idea to verify that the mirror is resting solidly on it's stops.

  7. #7

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    Hmmm, of coarse, this is where I am at now, can focus close but not at infinity, so adjusting close in does not solve the problem.

    To address Bernard's comments, I am sure it is the focus screen position. When I took things apart, the adjustment screws were clearly just tightened to their stops. When I backed off just a bit, I could achieve focus at infinity. I agree that with the lens at infinity, the film plane was probably fine. The two cameras method is interesting, seeing as it is snowing outside at the moment, I will try this inside and see how it looks.

    I also have an old focus screen that I can cut to fit the film plane. I will try both methods to cross check each other. Once done, the proof will be in some photos.

    Thanks for the suggestions/guidance

    Joel

    Quote Originally Posted by E. von Hoegh View Post
    Close in does not verify infinity focus. You make sure the screen is square with the focal plane by placing the screen on the film rails. Good luck.

  8. #8

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    Something to keep in mind - lenses for SLRs very often focus slightly "beyond" infinity, to ensure that the lens will really focus at infinity on all camera bodies (slight manufacturing tolerances). This makes me suspect of the "two camera" method.

  9. #9
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    True, von Hoegh, and I sometimes get VERY annoyed when a wide angle ALMOST (but not quite) focuses to infinity. I usually take apart said lens and make a minor adjustment.

    But, all, don't forget this. As bernard_L infers, there is, indeed, a difference oftentimes between apparent (viewfinder) focus and real (film plane) focus, and such is usually caused by the mirror angle being a tiny bit off. Do this: take a picture of a 'picket fence' at 45 degrees with the lens wide open and camera rigidly mounted. Focus PRECISELY at a certain point, VERY carefully. Then process the somewhat underexposed negative and achieve a bit more contrast with extra development. Inspect the negative carefully in the enlarger. Find out exactly WHERE the REAL focus is. If it is EXACTLY where it was in the viewfinder, you are OK. But if it is off, that means that the mirror has to be a tiny bit raised or lowered. Some cameras let the mirror rest upon a set screw (Fuji ST series, Soviet Zenit) and some let it rest upon a metal prong (K1000, SRT). That front part of the mirror has to be either raised or lowered. Remember ALWAYS, that mirror has NOTHING to do with REAL focus and exists ONLY for 'telling' the viewer what is in focus. We do not want that informational feedback to be faulty!

    Make the slight adjustment so that the viewfinder and film plane are precisely aligned. Rule of thumb: If the viewfinder focus is BEHIND the film plane focus, the mirror needs to be slightly lowered. If the viewfinder focus is BEFORE the film plane focus, the mirror needs to be slightly raised.

    Easiest way to do this without going nuts: find, precisely, the exact location on the lens's distance scale that a random point on the picket fence is in precise focus ON THE FILM PLANE. Now you know the precise focus for that particular point. (Make certain that you can repeat this, including the precise position of the camera.) Then raise or lower the mirror so that, at that camera location, that point on the fence is in precise focus IN THE VIEWFINDER. You will have matched viewfinder with film plane. Of course, again, keep the lens WIDE OPEN so that you limit depth of field.

    Finally, for those brave souls who find this 'fantasy' I have posited too unbelievable to believe: take sliver of paper (about the thickness of a postcard) and carefully place it under the mirror at the point where the mirror rests upon (ie, set screw or prong). NOW, put the lens on the camera and focus. You will think that you are focusing at infinity when you will REALLY be focusing at about 15 feet. In other words, if you took a picture, you would THINK that focus should be at infinity but it would REALLY be at about 15 feet.) In this case the mirror needs to be lowered (ie, lowered, because the paper raises it too high!). In other words, (see FIRST 'rule of thumb, above) the mirror (with paper underneath) is causing the viewfinder to seem to focus at infinity when the REAL (film plane focus) would be at only about 15 feet.

    Moral of the story: tiny differences in mirror height make quite a difference in matching viewfinder information with actual information. - David Lyga
    Last edited by David Lyga; 04-18-2013 at 04:18 PM. Click to view previous post history.

  10. #10
    ic-racer's Avatar
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    Additional info on mirror alignment here: http://www.apug.org/forums/viewpost.php?p=1225528

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