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03-05-2011, 06:45 AM   #1
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Ghosting/focus issue on reassembled vivitar 28-90

Hi all,

First time poster looking for help on a lens issue. I purchased my second older manual lens off Ebay recently for our kX, a Vivitar series 1 28-90 f2.8, and got burned by oily aperature blades. On closer inspection, I could tell the lens has been apart before I got it, as the lens spanner holes are all dinged/scratched... But, The lens did take respectable photos when I received it, with the exception of the slow aperture.

So I took it apart, attempted to clean the blades with alcohol which made a slight improvement but its still 'slow', and reassembled.

Now, the lens takes respectable photos when zoomed at the wide end and focused close, but when zoomed from 50-90 mm, everything has ghosting and halos around it (see attached). What might cause this? Would dust or residue on an element do this, or is it more like a flipped element affecting focus at the tele end? I know I got a bit of alcohol on the element behind the aperture, but I got it pretty well wiped and streak free. I think the mistake I made was removing the mount end lenses, which didn't need to be touched for access to aperture (doh ).... but I'm confident they are installed as they should be (I found a cross section of this lens which really helped).

Any suggestions on either the ghosting or getting the aperture better (especially the ghosting!)? I'm not out a bunch of money, but would love fix it and keep it, I hate junking anything.

thanks for any guidance!
Eric

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Last edited by eabrust; 03-05-2011 at 11:59 AM.
03-05-2011, 08:13 AM   #2
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Eric, first off, welcome to the Pentax Forum!!

Second, since it took 'decent' photos prior to disassembly, sure sounds like one of the elements got reversed. However, if you have a real bright light (LED flashlight or ....) shine it through the lens and look very closely for "stuff" on the lens surfaces - look as much on an angle as possible as that will show stuff better than looking straight through the lens. Good luck.
03-05-2011, 08:53 AM   #3
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Only time I've seen something like that is when an element isn't aligned properly (eg. it's not directly perpendicular to the focal plane.) I'd check to make sure that all the elements are seated correctly.
03-05-2011, 09:26 AM   #4
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I would make sure all the elements are seated properly. Also make sure that whatever groups are screwed in are tight.



03-05-2011, 11:52 AM   #5
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Thanks all for the suggestions and help.

It must have been a slightly tipped element... after reassembling about a dozen more times, seemingly the same every time, it is finally spitting out decent images (at least as well as I can take them) across the zoom range. I have a new found respect for engineering behind optics.... and it was a good learning lesson...

I still have a fairly slow aperture in this lens despite the cleaning. They used a lot of grease in these lenses back in the day... While it takes decent pics wide open, it would be nice to have some control... any recommendations on what you would do? The ring operates the aperture fine and smooth, its just to slow on release to close down during a photo with reasonably fast shutter speed. Is the best thing to clip the actuator tab and make it full manual? I haven't had the Kx long, but can you make it close the aperature manually before hitting the shutter? I plan on using this lens only indoors low light with the kids mostly.

Thanks again!
Eric
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03-05-2011, 12:37 PM   #6
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Eric, couple of things you can do:

1) take it all apart (again!!) and use some electronic contact cleaner on the blades - it won't leave a residue and will (should) cut through the grease. Just make sure there's no glass in the lens when you do this.

2) Send the lens to a repair guy - don't know if Eric Hendrickson (pentaxrepairs@aol.com) works on the viv lenses, but he's highly regarded on this forum for Pentax SLR repairs (I've used him several times) OR

send the lens to Ralph Innes (rhinnes@shaw.ca) in Canada - he's worked on several of my lenses and I recommend him highly.
03-05-2011, 05:09 PM   #7
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QuoteOriginally posted by ChipB Quote
Eric, couple of things you can do:

1) take it all apart (again!!) and use some electronic contact cleaner on the blades - it won't leave a residue and will (should) cut through the grease. Just make sure there's no glass in the lens when you do this.
Exactly - alcohol is good for cleaning glass but isn't dissolving the oil. I use mineral spirits. Not odorless, because its formula evaporates too slowly. If you're trying to clean the aperture without removing individual blades, it can take several tries to get all the oil removed.
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