Taking apart and cleaning Oreston 50mm 1.8 (zebra)

[secludedsea]

I managed to find yet another Oreston lens pretty cheaply. It was dusty, which was easy to clean, but I noticed what looked like spots of fungus underneath the front element.

This lens is not hard to take apart. The retaining ring is a single piece with the name ring, and once the tiny screw is undone, it will screw out easily. This reveals a few concentric retaining rings that need to be unscrewed before the barrel containing the front glass elements can slip out. This leaves the empty barrel with the aperture mechanism and the back element.

There's another retaining ring holding the front element in place and mine was a bit stiff. I had to use calipers to loosen it up. Once this as done, the front element comes out easily and can be cleaned. To my surprise, I discovered that the fungus was not behind the front element at all. It seems to have been on the outside of it and then cleaned off at some stage, leaving small spots of coating loss or etching. No big deal. There's not much there at all. You can see these little spots in one of the photos.

I haven't managed to get the grub screw back in place, but that's no big deal really.

[jamaeolus]

Good work.

[KEO]

Yes, nice job.

I have one of these Orestons but luckily it's not in need-to-open shape.

[tomasg]

Put some polishing cream for metal on the threads of that front ring that has the letters printed on. Tighten and untighten it, until you reach the exact position where the tip of that screw reaches it s correct position, there should be a small depression/mark left on the barrel. Untight and clean the threads, screw back the ring, insert the grub screw. The polishing paste works really well, but it must be for metal, the finer ones for car painting don t work so well.

[braz]

Great lens, I buy them whenever I see them for $30-35. Have fully CLA'd 5 or 6 of them, kept 3 that turned out really well.