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06-16-2010, 10:11 PM   #1
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Zenitar and infinity focus

I just got a Zenitar 16mm FE and its infinity focus is about 2 feet:

f/5.6
http://imgur.com/YYIZF.jpg
f/8
http://imgur.com/b1cux.jpg

At infinity, it seems a tiny amount af space between the focus ring and the front part:
http://imgur.com/mWxbw.jpg

Here is at close focus, for reference:
http://imgur.com/IW61D.jpg

At infinity, the marker is right in the middle of the infinity symbol. Is this fixable?

I am going on a trip soon and wanted to bring this lens. I also am quite uncomfortable opening it up, I have broken things before, if anyone knows anyone around Columbia, MD.

06-16-2010, 10:46 PM   #2
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A common problem with the Z. Yes it is fixable - I don't know about this forum, but there have been threads on it on dpreview. It's a bit fiddly but with the right screwdriver easily done. Unfortunately I destroyed one of the screw heads, so having slightly over-adjusted mine I cannot easily redo it. I haven't got time now to type out the step-by-step but it's very simple. Do a search on DPR.
06-17-2010, 12:32 AM   #3
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QuoteOriginally posted by timo Quote
A common problem with the Z. Yes it is fixable - I don't know about this forum, but there have been threads on it on dpreview. It's a bit fiddly but with the right screwdriver easily done. Unfortunately I destroyed one of the screw heads, so having slightly over-adjusted mine I cannot easily redo it. I haven't got time now to type out the step-by-step but it's very simple. Do a search on DPR.
There are good directions at the pentax-lens-and-japanese-doll-site:

Zenitar 16mm f/2.8 Fisheye

(look under "Don't Panic")

A few things to note:

(0) If in doubt, consider returning it.

(1) Don't expect this lens to be sharp at f/2.8. If you get an acceptable result at f/4 and slower, you're done.

(2) The infinity marker will hit the index mark whether this lens is properly adjusted or not.

(3) Use the properly sized screwdriver and press firmly to seat the screwdriver in the screw slot

(4) There's a good chance you can get the focus ring loose even and make the adjustment if you can loosen only two out of three screws.
06-17-2010, 10:23 AM   #4
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Some other tips:

-You're only adjusting the infinity focus stop by doing this, you don't have to worry about messing up the mechanicals. Take your time and adjust it a little at a time, testing as you go. When your far images get blurry again, you've gone too far.

-You only need to loosen the screws enough to move the focus ring freely. You don't need to remove the screws.

-You may have to adjust the hood during or after adjusting the focus, the focus ring can bump up against the hood the further out you focus.

06-17-2010, 10:37 AM   #5
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I was playing around with this and am having trouble achieving infinity focus. The focus ring gets flush with the part in front (and the focus ring is not at infinity yet), and objects say 50 ft start getting more in focus but never in focus (and don't start getting less in focus). Objects like 10 ft do get in focus and then less in focus.

The lens hood is off.
06-17-2010, 10:51 AM   #6
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QuoteOriginally posted by Eruditass Quote
I was playing around with this and am having trouble achieving infinity focus. The focus ring gets flush with the part in front (and the focus ring is not at infinity yet), and objects say 50 ft start getting more in focus but never in focus (and don't start getting less in focus). Objects like 10 ft do get in focus and then less in focus.

The lens hood is off.
Send it back.

The usual adjustment required is only a few degrees of arc and about a millimeter of so of travel. If you are up against the front bezel, the lens is not just a "little out of adjustment", it is defective.


Steve

BTW...the best way to dial in a Zenitar 16/2.8 is to mount it on a body with a split-image focus aid, say an older film camera and use a large building or some other hard-edged object some distance away as the infinity focus target. I can tell you from experience that "eyeballing it" or using focus confirm does not work very well.

Last edited by stevebrot; 06-17-2010 at 10:59 AM.
06-17-2010, 11:36 AM   #7
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I wish I had a split-image, I was thinking about that earlier. I'm using 10x magnification in liveview and taking bursts on a tripod.

Wait a minute: I just read that the clear filter on the back is necessary. I thought it was one of the color filters and took it off, since I like less glass in the way. Looks like I'll need to do some more testing tonight. Some reported being able to adjust it to infinity focus without it. Anyone experience here?

Last edited by Eruditass; 06-17-2010 at 11:46 AM.
06-17-2010, 11:51 AM   #8
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QuoteOriginally posted by stevebrot Quote
Send it back.

The usual adjustment required is only a few degrees of arc and about a millimeter of so of travel. If you are up against the front bezel, the lens is not just a "little out of adjustment", it is defective.


Steve
When I adjusted mine I guess it needed about 2-3mm of adjustment to get it right.

Tim

06-17-2010, 02:42 PM   #9
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QuoteOriginally posted by Eruditass Quote
I wish I had a split-image, I was thinking about that earlier. I'm using 10x magnification in liveview and taking bursts on a tripod.

Wait a minute: I just read that the clear filter on the back is necessary. I thought it was one of the color filters and took it off, since I like less glass in the way. Looks like I'll need to do some more testing tonight. Some reported being able to adjust it to infinity focus without it. Anyone experience here?
Yes, there has to be a rear filter in place. That is from the translated Zenitar manual:

QuoteQuote:
Before mounting the lens on to the camera remove the lens rear cap. Make sure of the light filter compensator 4 (a clear glass plate in holder, screwed into the lens) being mounted on the lens.
As for the split image...Do you know anyone with a K-mount film camera that you can borrow for a few hours?


Steve

Last edited by stevebrot; 06-17-2010 at 02:57 PM. Reason: Added quote from user manual
06-17-2010, 02:44 PM   #10
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QuoteOriginally posted by Eruditass Quote
I wish I had a split-image, I was thinking about that earlier. I'm using 10x magnification in liveview and taking bursts on a tripod.

Wait a minute: I just read that the clear filter on the back is necessary. I thought it was one of the color filters and took it off, since I like less glass in the way. Looks like I'll need to do some more testing tonight. Some reported being able to adjust it to infinity focus without it. Anyone experience here?
I believe you need the clear filter in place for it to render properly (although I'm not exactly sure what happens if it is off).
06-17-2010, 02:53 PM   #11
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QuoteOriginally posted by timo Quote
When I adjusted mine I guess it needed about 2-3mm of adjustment to get it right.

Tim
The OP was up against the front bezel of the lens. That is the absolute limit for travel. Something is very wrong if you can't attain infinity focus at the mechanical limit of the helicoid.

As for adjustment...the total linear travel on the Zenitar (lock-to-lock, 10" to infinity) is only 2mm. If yours required 2-3mm adjustment, it must have made for a real cool close-focus lens



Steve
06-17-2010, 03:05 PM   #12
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QuoteOriginally posted by anthers Quote
I believe you need the clear filter in place for it to render properly (although I'm not exactly sure what happens if it is off).
Hah!

Mystery solved!

I just happen to having my Zenitar very handy to the computer and having nothing better to do, I took off the rear filter and mounted the lens on a camera with a split image finder. What happens?
You Lose Infinity Focus!!!
In fact, you lose it in a major way. How does 5' instead of infinity sound?


Steve
06-17-2010, 03:48 PM   #13
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Mine had 2' infinity focus without it! It probably had some issues with it on, but I'll never know. Maybe one day I'll run across a pentaxian that has a split-image screen. I'll have my screwdriver ready. Thanks guys.
06-17-2010, 11:44 PM   #14
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QuoteQuote:
As for adjustment...the total linear travel on the Zenitar (lock-to-lock, 10" to infinity) is only 2mm. If yours required 2-3mm adjustment, it must have made for a real cool close-focus lens
Steve
Er.. well.. I was talking about focusing ring travel
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