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09-25-2008, 02:41 PM   #1
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zentar 16 won't infinity focus??

Just received my new toy via ebay... For some odd reason this lens won't infinity focus on my k10d? Any ideas? It looks good...

09-25-2008, 03:29 PM   #2
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QuoteOriginally posted by milapse Quote
Just received my new toy via ebay... For some odd reason this lens won't infinity focus on my k10d? Any ideas? It looks good...
Hi,
This is a historic problem with the Zenitar. My understanding had been that the factory had figured out how to adjust these things before sending them out the door. Wrong again.

There are several instruction sets on the Web, but I can give you the basics of adjusting the focus ring here.

First off...The whole process is easier if you have, or can borrow, a body that has a split image focus aid in the viewfinder. The split image allows you to see easily when your adjustments are spot on.
  1. With your fingernail or a small screwdriver, carefully lift the edge of the rubberized surface on the focus ring and push the rubber piece up and completely off the focus ring so that the focus ring turns freely without binding on the rubber.
  2. Using a jeweler's type slot screw driver, loosen the first two screws, leaving the one nearest the top for last.
  3. Carefully loosen the last screw and move the ring a few degrees to the left.
  4. Tighten the screw and check the infinity focus through the viewfinder.
  5. Repeat the steps 3 and 4 as needed.
  6. Tighten the other two screws and replace the rubber focus grip.

The main caution is to not over-tighten the screws. The metal is pretty soft and you do not want to strip the heads. In rare cases the built-in "hood" may be seated too close to allow the barrel full travel inwards. In that case you will have to loosen the hood as well. If this is the case, be very careful with the screws that secure the hood. They are very small and have very fragile heads.

Steve

P.S. Mine came from the factory essentially in proper adjustment and was working fine from my perspective until I was using it on my 35mm SLR. It was then that I noticed that the split image was not lining up for distant objects. It was only off about a few degrees, but I did the adjustment anyway. It only took about 15 minutes.

Last edited by stevebrot; 09-25-2008 at 04:24 PM.
09-25-2008, 04:28 PM   #3
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Do you know if other lenses have this same form of adjustment? I have a manual 200 that I have added shims to the mount face to get it to line up correctly, however, this is a more elegant solution than pieces of shim stock cut in a circle to get things to line up correctly.
09-25-2008, 04:46 PM   #4
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QuoteOriginally posted by sabarrett Quote
Do you know if other lenses have this same form of adjustment? I have a manual 200 that I have added shims to the mount face to get it to line up correctly, however, this is a more elegant solution than pieces of shim stock cut in a circle to get things to line up correctly.
It is hard to say. I guess it depends on the manufacturer, though it is a fair assumption that they all have some way to true the focus ring to the internal stops.

Steve

09-25-2008, 05:12 PM   #5
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Thanks! so much! the k-1000 helped.. really not a bad lens @ F4! I had to to get it into the 'snuggly' racked back area before it lined up.

I'm going to check my takumars now...
09-26-2008, 09:45 AM   #6
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QuoteOriginally posted by sabarrett Quote
Do you know if other lenses have this same form of adjustment? I have a manual 200 that I have added shims to the mount face to get it to line up correctly, however, this is a more elegant solution than pieces of shim stock cut in a circle to get things to line up correctly.
Probably all lenses have some form of adjustment for infinity focus. The Takumars and Pentax prime lenses usually have three screws hidden behind the ring around the front lens element. (This is often the ring engraved with the lens's name.) With these screws loosened, the focus ring turns without changing the actual focus. The focus ring has a mechanical stop at infinity.

I use my film camera because it has a larger viewfinder with a split prism. I put it on a tripod, mount the lens, tighten one screw, set the lens at the infinity mark and try to focus on a convenient distant object. If I can't focus that far, loosen the screw, turn the focus ring a bit away from infinity, tighten the screw and check it again. If I can focus "to infinity and beyond", focus at infinity, loosen the screw, turn the ring to the infinity mark and tighten all the screws.

I have had a few zoom lenses that were adjusted by loosening a lock ring and moving the front element, which is in a threaded mount. The Pentax-F 70-210mm, the Takumar-A 70-200mm f4 and the Pentax-A 80-200mm zooms were all like that. Note that zoom infinity focus needs to be checked at both ends of the zoom range.

The Vivitar Macro Focusing Teleconverter adjusts by peeling back the rubber focus grip, which holds two rings together. The rings can then move independently. Be careful not to attempt to focus at the 1:1 end of the range until the rings and grip are glued back together, as the TC can come apart.
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