I may have posted something similar on this lens in the past, but my memory isn't that good anymore. Anyway, it's interesting, to me anyway.
I bought this Leica R 90 2.8 Elmarit cheaply because it was advertised as having coating blemishes in the rear element that could not be removed. Turns out it wasn't in the coatings, it was in the glass itself. Someone had removed fungus from it, and the rear element now looks like it has salt sprinkled all over it from the fungus etching, and is very rough to the touch. It has a dull look to it when you look through it. The CLA person also lost the shim to the rear element, and it would not focus to infinity. It stopped around 50 feet. I shot a quick test roll and the shots were soft under f8 at infinity, stopped down more they looked nice and sharp. So I pulled the rear element out (surprisingly easy) and kept dropping thin washers that I bought from the hardware store into the lens, then putting it back together and checking focus. Eventually I found one that worked well, even though it was a lot fatter than the lost original shim and showed quite a bit when you looked at it from the rear or the front (see third shot).
So how does it image? It works fine. No flare, and sharp as a tack even wide open. I was shocked, as I've always been a stickler for clean glass, especially on a Leica lens. I guess the moral of this is, don't give up on a lens just because the glass is not good. Give it a test and see how it works. The first sample shot is at f4, the last shot is wide open.
I bought this Leica R 90 2.8 Elmarit cheaply because it was advertised as having coating blemishes in the rear element that could not be removed. Turns out it wasn't in the coatings, it was in the glass itself. Someone had removed fungus from it, and the rear element now looks like it has salt sprinkled all over it from the fungus etching, and is very rough to the touch. It has a dull look to it when you look through it. The CLA person also lost the shim to the rear element, and it would not focus to infinity. It stopped around 50 feet. I shot a quick test roll and the shots were soft under f8 at infinity, stopped down more they looked nice and sharp. So I pulled the rear element out (surprisingly easy) and kept dropping thin washers that I bought from the hardware store into the lens, then putting it back together and checking focus. Eventually I found one that worked well, even though it was a lot fatter than the lost original shim and showed quite a bit when you looked at it from the rear or the front (see third shot).
So how does it image? It works fine. No flare, and sharp as a tack even wide open. I was shocked, as I've always been a stickler for clean glass, especially on a Leica lens. I guess the moral of this is, don't give up on a lens just because the glass is not good. Give it a test and see how it works. The first sample shot is at f4, the last shot is wide open.