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Mike_rgb
Tinkerer
Username: Mike_rgb
Post Number: 5
Registered: 08-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, October 11, 2006 - 12:35 am: | 
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Hello All.
I have a SIGMA ZOOM 28-80mm 1:3.5-5.6 MACRO Lens made for NIKON. It has Aspherical 28-80 mm D & a small slide switch with normal & macro at 80 on the outside.
The mounting plate has 4 black phlips screws & a small white metal regular screw. The lens has been loose & not smooth when focusing. I have used it with both of my FEs & have had some clear Macro pics of Mushrooms.
What is the silver regular screw for? I can turn it counter clockwise & it locks the lens up. When I turn it clockwise everything gets loose & very sloppy. Is there a standard adjustment for this screw? I only gave $15 at a flea market but it does take a nice clear picture & I would like to fix it If possable.
Thanks in advance.
Mike |
Glenn
Tinkerer
Username: Glenn
Post Number: 70
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, October 11, 2006 - 08:42 am: |
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It sounds like the 'silver' screw takes up the backlash/free play in the helical. If it were me, I would turn the screw counter clockwise until the lens locks up, then back it off until you get a smooth movement with the minimum of slop/free play. You can then secure the screw head with a dab of nail varnish.
If the above does not give an acceptable 'feel' to the operation, you will have to relube the lens. As I have no stripdown experience of this lens, I an unable to help you further. |
Mike_rgb
Tinkerer
Username: Mike_rgb
Post Number: 6
Registered: 08-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, October 11, 2006 - 02:24 pm: |
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Hi Glenn
I tried turning the screw out until it locked & then tried power, focus adjustments. I was surprized to see as I worked the rings it was not really locked so I backed it out again & again.
It was then I noticed the 80mm mark was way past the heavy white line. So I turned the screw back in until the 80mm mark was lined up with the line. When I turned the power ring back it lined up on 28mm mark.
It seems this screw may be an adjustment for lining up the power settings. Not once did the focus ring ever become smooth to turn no matter where the screw was set. The focus ring feels very rough while turning either way. This is the same rough grating on both the normal & Macro settings.
I only have one other AF lens a Nikor 75-240mm D. It is has a smooth focus adjustment also the objective lens moves in and out like my MF lenses do. None wiggle or have scratch marks on their tubes. I feel that the main problem is in the focus area of this lens, everything else seems to work fine.
Finding a blowup or repair manual for this Sigma seem like a good place to start my first lens tear down, & reassembly. I remember reading ( Good lens seldom ever get sold ) when I first got started in Photography. Where does a SIGMA lens fit on the quality ladder?
Mike |
Glenn
Tinkerer
Username: Glenn
Post Number: 72
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, October 11, 2006 - 08:22 pm: |
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Mike,
You are correct about that screw, remembered reading something on one of the Sigma sites after I had replied to your post.
My son has a good selection of Sigma optics for his SD9. The cheaper 'kit' lenses are a bit 'cheapo plastic' in feel and construction, however optical performance is OK for price. The EX range of Sigma lenses are very good in all departments and my son's examples have proved to be very good performers. The two original 'kit' lenses have not been used much. This is probably a good thing because there was 'slop' in both inner barrels from new. I suspect they would be really worn, if he had used them as much as the EX lenses.
I suspect that you will find the auto focus mechanism well worn, when the lens is opened up.
Yes we do tend to hang on to good lenses. And if they are sold on, we always bloody regret it later! |
Mike_rgb
Tinkerer
Username: Mike_rgb
Post Number: 7
Registered: 08-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, October 12, 2006 - 12:35 am: |
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Well I thank you kindly for your help Glenn. I know it seems a bit crazy to some, trying to make their trash into treasure. I can't pass an older camera or lens at a yard sale or flea markt.
I was born in 51, my house was built in 51, & the Sears Generator we rely on was sold by Sears in 51. Who knows maybe they will find a cure someday, I sure hope it's not in my lifetime LOL.
Mike |
