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  1. #21
    David H. Bebbington's Avatar
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    There does remain the problem of what to do with lenses with non-standard filter threads (or none). I have 2 barrel lenses on Sinar panels where I have superglued a Cokin holder to the rear of the panel, leaving the front free for an add-on shutter, and I did even superglue a stepping ring to the front of a 168 mm Angulon so that I could use standard filters. This particular lens had a front which was too small for my standard oddball filter solution, which is a Cokin filter holder with 3 pinch screws instead of a threaded ring.

    I am sure Donald is right in suggesting that T-mount adapters can seize onto lenses. My worst experience of aluminum corrosion of this kind was changing the plug on a lawn mower which had a Briggs & Stratton engine. The plug had been in for about 3 or 4 years, when I unscrewed it the plug came out complete with the plug hole and a disk of surrounding metal 3 or 4 mm thick. This was one of those few occasions when superglue was not able to effect a repair

    Regards,

    David

  2. #22

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    Donald, galling/corrosion is an interesting and scary idea. But all of the T-mount (including T2s and reverse T) adapters I own are hard anodized and so are all of the T-mount devices I own. That's why I suspect glue on my 400/6.3 cheapy.

    Cheers,

    Dan

  3. #23
    Donald Qualls's Avatar
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    Unfortunately, galling can take place even on hard anodized parts, especially if accelerated by corrosion. Aluminum doesn't "rust" but that's because "rust" refers only to hydrated oxides of iron. The oxide layer that protects aluminum (and which is artificially thickened and often colored in the anodizing process) can be destroyed very quickly by enough pressure to deform the relatively soft metal under the super-hard but brittle oxide (essentially polycrystalling sapphire), which could occur if the adapter were tightened with grit in the threads; moreso, aluminum oxide and then the metal undeneath will literally dissolve in water with significant chloride ion (like sea water, sweat, etc.), causing corrosion pitting, redeposition, and what amounts to welding.

    If David has been at your lens and super-glued the ring in place, you might be able to debond it with acetone (I'd suggest standing the lens, big end up, in a tiny cup of the stuff and checking it every few hours for as much as 2-3 days -- but beware of the flammability of acetone vapor!), but if it's galled or corroded in place, the only solution would be to cut most of the way through the ring (very careful application of a hacksaw or rotary tool with cutting wheel), insert a screwdriver in the cut and twist to break the remaining metal in the threads, and then pry the ring open to get it off the lens threads; more or less like splitting a seized nut off the bolt. This will likely work if it's glued, too, but either way there's a very distinct possibility of completely destroying the rear section of the lens (in case you're not aware, the Spiratone 400/6.3 comes apart at the tripod mounting ring).

    Meanwhile, I think I'll pull the T-ring off mine and give it a very light coat of the Superlube Teflon grease I keep around for stuff that needs to stay slick...
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

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