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Ektar rear element cleaning

 
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bruiser



Joined: 15 Oct 2006
Posts: 259
Location: Northern NSW Australia

PostPosted: Thu Oct 29, 2009 11:07 am    Post subject: Ektar rear element cleaning Reply with quote

Hi all,

Is there a relatively painless way of separating the rear elements of an Ektar lens? I have a 105mm f3.7 that has a little fungus BETWEEN the rear elements, not at the front or back of the group. Does one of those push'n'grip circular rubber do-hickeys work in this instance?

Thanks,
Bruce
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45PSS



Joined: 28 Sep 2001
Posts: 3201
Location: Mid Peninsula, Ca.

PostPosted: Thu Oct 29, 2009 4:36 pm    Post subject: Reply with quote

Looking at http://www.cameraeccentric.com/html/info/kodak_4.html (catalog page 57) the rear element is a cemented pair. Unscrew the rear cell from the lens then on the shutter side of the cell there should be a retaining ring/cap that unscrews allowing the element to be pushed out. If there is no retaining Ring/cap then the edge is folded over to hold the cell in place.
What you are seeing may be separation, not fungus. Fungus is killed by Ultra Violet light. Lay the lens cell in direct sunlight for a day or two to kill the fungus in any lens. Ensure that the fungus is exposed to direct sunlight and not shadowed by the barrel of the lens.
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bruiser



Joined: 15 Oct 2006
Posts: 259
Location: Northern NSW Australia

PostPosted: Thu Oct 29, 2009 8:53 pm    Post subject: Reply with quote

Thanks 45PSS!!

It's definitely fungus, lots of fine spidery filaments, so I'll try the sunlight option first (plenty of that here in Australia).

Many thanks,
Bruce
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Dan Fromm



Joined: 14 May 2001
Posts: 1881
Location: New Jersey

PostPosted: Thu Oct 29, 2009 10:11 pm    Post subject: Reply with quote

Hi, Bruce. I just took a close look at my 105/3.7's rear cell. Use a magnifier on yours.

As you've been told, the lens is a heliar type, has a cemented doublet at each end and a singlet in the rear cell facing the diaphragm.

As best as I can tell, the rear cell's outer group, its cemented doublet, is swaged in. Its there to stay.

But the inside of the rear cell, facing the diaphragm, is threaded. It looks like the singlet you'll have to remove to get to the singlet and rear doublet's inner surfaces is held in place by a retaining ring. Artful use of a rubber cork the right size might unscrew the ring.

Good luck, have fun,

Dan
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bruiser



Joined: 15 Oct 2006
Posts: 259
Location: Northern NSW Australia

PostPosted: Thu Oct 29, 2009 10:29 pm    Post subject: Reply with quote

Thanks Dan!

I might just give the rubber cork a try as the sun has just decided to hide behind a very large cloud and the UV rays are disappearing.

Cheers from Oz,
Bruce
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45PSS



Joined: 28 Sep 2001
Posts: 3201
Location: Mid Peninsula, Ca.

PostPosted: Fri Oct 30, 2009 4:48 am    Post subject: Reply with quote

Bruce,
The UV will kill the fungus but to remove it you will have to remove the element and clean it with methyl alcohol or methyl ethyl ketone.
Somewhere on this site or photo.net I read a procedure for opening lens barrels that were rounded over to hold the elements in but I cannot find it.

The procedure was basically to use a very small slot jewelers screw driver inserted between the glass and edge of the rolled over barrel (usually brass) and gently pry up the metal .001 to .002 inch working around the edge until the metal has been raised an equal amount around the element then repeat as many times as necessary to get the metal clear of the lens elements. The trick is not to move the metal too much so that it does not break and of course not scratch the glass.

Reference:
http://photo.net/large-format-photography-forum/005nGW
http://photo.net/large-format-photography-forum/005O9e
http://photo.net/nikon-camera-forum/00LRLu
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bruiser



Joined: 15 Oct 2006
Posts: 259
Location: Northern NSW Australia

PostPosted: Fri Oct 30, 2009 8:00 am    Post subject: Reply with quote

Thanks again for the info and for the links as well. I tried a little UV today but will A. try to get into those elements or B. hope for more sun over the weekend.

Cheers,
Brue
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45PSS



Joined: 28 Sep 2001
Posts: 3201
Location: Mid Peninsula, Ca.

PostPosted: Fri Oct 30, 2009 5:04 pm    Post subject: Reply with quote

My Nikor 35-135 developed fungus in the rear element. I removed the elements, laid them on a sunny window sill and let them lay for 2 or 3 days. Killed the fungus. I would be hesitant to use some of the chemicals mentioned in the links on the coated side of the elements. I hope the glass is not etched. It is doubtful if the fungus will affect image quality unless it has etched the glass or is very heavy over a large section of the element.
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