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Message |
    
Richterjw
Tinkerer
Username: Richterjw
Post Number: 1
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 21, 2011 - 10:17 am: | 
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I have just acquired a Vivitar Series 1 28-105 f/2.8-3.8 for Minolta manual cameras(like my SRT 202). It is in immaculate shape aesthetically, but it does have one problem: it won't focus at infinity. The lens seemingly focuses correctly throughout the range, except at infinity; this is particularly noticeable when zoomed out to 105mm. Is there a remedy to this? I'm not super mechanically inclined, but am minimally capable. Thanks for any help. JR |
Old_school
Tinkerer
Username: Old_school
Post Number: 4
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 23, 2011 - 10:01 pm: |
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A friend has a Series 1 : 80-200 or so which he acquired new & it always focused past the infinity mark & the MFG did not make any adjustments they basically said that was the characteristics & it was good. I am not sure why , but if this is the same thing it may be the way the Series 1 lenses are configured to accept the different mounts. Not really sure. Let see if anyone else has some information on this topic, as I would like to hear other comments. Also check the focus without a filter on the lens. If you have one on it, as that could cause a shift. You have a lot of lenses out there with great optics & the owner puts a cheap filter on & that throws everything out of whack. The fiter quality can be seen on an autocollimator, it is very interesting to see. |
Richterjw
Tinkerer
Username: Richterjw
Post Number: 2
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 23, 2011 - 10:12 pm: |
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When I got it, it had a Hoya UV filter, but I have removed it. There was no noticeable different either way.
On another site, I was given the following instructions:
"Remove the front name plate by carefully flowing MEK or Acetone (No more than a tweezer dose) into the two tiny spanner wrench holes provided by the lens designers.
After a short wait to allow softening of the adhesive, unscrew the name plate ring. (You can use a rubber lens grip or hand drill two tiny dimples if you're afraid of using the two "close to glass" ones provided by Vivitar)
Apply a tiny amount of MEK or Acetone to the three set screws at the outside of the front tube.
Loosen those three screws and now the "filter thread tube" can be extracted.
Removed the "black tape" locking the front lens group from unscrewing.
Turn this front lens group until infinity is correct at the 105mm setting.
Re-assemble in reverse order."
However, I don't have the spanner holes mentioned in Step 1, and I wasn't sure whether drilling small indentations was a viable option. JR |
Michael_linn
Tinkerer
Username: Michael_linn
Post Number: 1
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 23, 2011 - 10:51 pm: |
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Vivitar had a number of subcontractors in Japan who made their lenses.
For starters, I would recommend that you try the lens out on another manual focus Minolta. If you get the same result, I would recommend that you just move on. Servicing a zoom lens of this vintage is a challenge without a lot of experience and written instructions.
This repair would not be my recommendation for your first project. |
Glenn
Tinkerer
Username: Glenn
Post Number: 914
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 24, 2011 - 07:18 am: |
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I would certainly agree with the comments by the last contributor. Also, one should never start applying Acetone or MEK into a lens assembly (however small the amount), until one is well versed in methods of lens construction and the assembly techniques used. Applied wrongly or wicking through to hidden plastic parts, can leave the whole assembly welded solid.
On your query on lack of infinity focus, are you actually sure that you are not muddling focus shift with inability to focus at infinity? The type of focus screen fitted can also play an important part in the ability to judge actual focus point - although in your case the particular lens should function with the standard SRT 202 screen. Never try and judge focus shift or point by initial focus at the short focal length end of the scale, always focus at the maximum focal length and then zoom in to make your assessment.
You indicate that this lens appears clean and tidy - zoom lenses from this era are notorious for 'sucking in' large amounts of dust which will settle on the internal surfaces of the optics. Unless your lens has seen very little use, I suggest that it has been stripped and cleaned by somebody who had little or no knowledge of the correct set up techniques. With your self admitted lack of experience I doubt if you can strike lucky and correct the problem - although over the years I have come across a number of people who have been extremely lucky in their ignorance! |
Old_school
Tinkerer
Username: Old_school
Post Number: 6
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 25, 2011 - 01:13 am: |
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Try a ground glass on the film plane to check the focus.
Shutter on B locked open, on a tripod & a real far off distant object for infinity. This will also let you know if the finder focus is giving a true perspective. |
Richterjw
Tinkerer
Username: Richterjw
Post Number: 3
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 25, 2011 - 07:02 am: |
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It shows the same inability to focus to infinity on two different cameras. I think I'll just put this in the cabinet for now, until some time in the future. Thanks, fellers. JR |
