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Minolta MD-II 2.8/135mm [5/5] fogged rear lenses
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PostPosted: Sun Mar 27, 2022 5:06 pm    Post subject: Minolta MD-II 2.8/135mm [5/5] fogged rear lenses Reply with quote

Some months ago I got my hands on a nice looking Minolta MD-II 2.8/135mm [5/5] without aperture mechanism. Since this version of the Minolta 2.8/135mm rarely appears on the market here in Switzerland, I bought the lens - just to get a good image for my website.

Recently I found another nice looking MD-II 2.8/135mm [5/5] along with a few other like-new lenses. For whatever reason I didn't check the rear side of the lens (the front was looking good), and when I cam home I found this:


Not lookin' good at all! ... Not only was the outer surface of the rear lens badly fogged, but the inner surfaces were affected as well. It was clear that I had to dismantle the lens, but it was not clear at all whether I would be able to clean and save it.

So first we remove the four bayonet screws:


Without further problems, the entire bayonet including the aperture transmission mechanism comes off. Very well done:


Now, looking down into lens barrel, we can see three screws holding the real lens system in place:


When we remove them, the rear lens system comes out:


It turns out that the small barrel holding the real lens is manufactured from plastic. The lens itself seems to be glued into the plastic piece. No screws, threads or other mechanical parts can be seen. This construction certainly is very different from what can be found in earlier (AR/MC/MD-I) Rokkors! Cleaning the rear lens turns out to be impossible; some agent (glue??) seems to have etched both surfaces.

At this point my first MD-II 2.8/135mm comes into the game - its rear lens looks much cleaner (though not really clean), and so intend to use that one. Scrubbing and washing makes the second one looking fairly good.

Looking closely at the front group I can see some spots of fungus, and therefore I decide to swap not only the rear part, but also the front part of the lens. This is even easier than swapping the rear part (which was very easy anyhow). One just has to un-screw the single tiny screw shown here (it's the one closest to the front - there are three other screws visible: leave them untouched). Apply some acetone to the screw before taking it out - it seems to have been glued in:


Now the front group can be taken out (un-screw it from the front):


Swapping the lens groups and re-assembling is trivial, so no more pics here! The entire process is extremely easy, certainly something any beginner can do without running into problems.

S


Last edited by stevemark on Mon Mar 28, 2022 2:39 pm; edited 2 times in total


PostPosted: Sun Mar 27, 2022 6:28 pm    Post subject: Reply with quote

I have got a box of bits for that lens, there's a set of blades, spacers and screws, and good glass except that rear block. I might have the body? but I can't see it at the moment.

I guess my lens had the same problems with that rear block. I have got a good one though, its a nice lens.


PostPosted: Sun Mar 27, 2022 7:50 pm    Post subject: Reply with quote

Like 1

Most of those MDI/MDII 135mm Rokkors are easy to get into.

During the MDI/II/III era for some lenses Minolta started to switch to these burnished lens mounts, as opposed to the earlier threaded retaining ring mounts. Great for reducing production cost, but a pain for maintenance. The only way to fix these is to cut / file / machine off the overturned brass or plastic lip, and later cement the lens back into place after cleaning. If the lens mount consists of both a burnished edge and adhesive, it is pretty much game over.

I once removed the element of a Minolta MDIII 50mm f/1.7 with an identical looking burnished retainer; that turned out to be just a plastic burnished lip, no adhesive, and came out fairly easily with a lens sucker (after carefully cutting off the lip with a very sharp knife). They probably use a brief application heat in the factory to permanently deform that plastic lip. To remount it I used some plastic model glue around the outer edge, which is essentially just some polystyrene dissolved in MEK. Seems to have held up well so far.

Those white spots on the rear light baffle isn't fungus, but a degrading/decomposing flocking paint. A lot of these 135mm Rokkors have that problem. That old paint comes off clean with some isopropyl alcohol & stiff rubbing. I usually just repaint with a matte black model paint. Not quite as black as flocking paint, but good enough for me.


PostPosted: Mon Mar 28, 2022 2:04 am    Post subject: Reply with quote

I have this same lens and it also has a problem with the rear element. But instead of it being all fogged up, it has lots of tiny little pits in the coating -- or I guess it's in the coating. At any rate, no matter how much I try cleaning it with lens cleaning fluid and lens paper, it doesn't make a bit of difference. Definitely not fungus, or even haze. Tiny pits.

This lens was part of an outfit I bought, so I'm not too stressed out about it, but it would have been nice to get it back going again. But given that all this damage is on the rear element, it's pretty much junk -- unless I can figure out how to remove the coating without damaging anything else.


PostPosted: Mon Mar 28, 2022 9:16 am    Post subject: Reply with quote

Nice work!


PostPosted: Sun Nov 27, 2022 1:06 am    Post subject: Reply with quote

I had a similar problem with my MD-II 2.8/135, which had cristalline like patterns on the rear element, it didn't look as fogged though. Sadly, I forgot to take any pictures of it. Anyway, with mine the element seemed to be just pressure fitted into the plastic barrel and i was able to just push it out and cean it. I first tried it with alcohol, which didn't do anything, it all went away with some water and simple dish soap though.
...Also from Switzerland btw 😁


PostPosted: Sun Nov 27, 2022 11:44 am    Post subject: Reply with quote

chrysenteron wrote:
I had a similar problem with my MD-II 2.8/135, which had cristalline like patterns on the rear element, it didn't look as fogged though. Sadly, I forgot to take any pictures of it. Anyway, with mine the element seemed to be just pressure fitted into the plastic barrel and i was able to just push it out and cean it. I first tried it with alcohol, which didn't do anything, it all went away with some water and simple dish soap though.
...Also from Switzerland btw 😁


Keep an eye on that rear element.

I have had several Minolta lenses where water & soap *seemed* to clean off the surface haze/residue, but once the surface dries again properly (which may take a day or two), the haze comes back. I therefore suspect that in my case the haze may have had some properties that once wetted seems to clear, but holds on to the moisture for a while and when it finally does dry properly, returns to its hazy consistency. I'm no expert on polished glass surface structure, but perhaps it has something to do with a compromised silica-gel layer (resulting from one of the chemical mechanisms involved in surface polishing.) Hoya once referred to that type of surface damage as "dimming", primarily caused by long-term exposure to condensation which leaches alkali ions from the surface layer which then erode the silica-gel layer (Izumitani, T.S., Optical Glass, 1985)

Hopefully in your case it is something different and the haze stays away Happy Dog


PostPosted: Sun Nov 27, 2022 11:51 am    Post subject: Reply with quote

I've opened to clean 2 of the 135mm nFD 2.8 ,both of them with haze in front group , couldn't remove only about half of it.
It would be nice to have a thread for the bits of opened lenses as donors. The 2 of them are RIP just like the 35-70 zoom and another smashed 50mm 1.8, and just don't feel comfortable to throw em in the bin.
By the way many thanks for wonderful explanation. The amount of plastics these Minolta's were using , seem in line with nFD ,at least the ones I've opened . , At least nFD have a click ring that's easy to open to remove elements.