Topcon 85mm lens

[mistertopcon]

I'm working on a Topcon RE 85mm f1.8 lens. The Iris blades are sticking. I tore it down to a state at which I'm sure I can get it back together again. I could not figure out how to get the front elements out. It sat on my desk for 4 months and I would look at it every few days and wonder. Finally after about the millionth look, it came to me. Out they came easy as pie. Now my next problem is how to get the rear element out. It won't twist. Will flexigrips work? My next problem will be to remove the iris and clean it. How does it come out. With the front elements out you can see it and those blades are as delicate as butterfly wings. I can see it resting on 4 little studs in the barrel so it must come out the back. This is a very rare, sharp as a tack, expensive lens. I'm NOT giving up on this lens.

[mickeyobe]

I know I keep repeating myself but since you are a newbie I'll go again.

Try a drop or two of lighter fluid.
Work the blades repeatedly.
Then do it again and again.
It is easy and often works wonders.
My motto is KISS.

MIckey

[Stephen]

Not knowing the Topcon internals, I would not normally advise, but they were very well built indeed, and I would be surprised if the trouble is the iris, it is more likely to be the ring around the unit, that is turned by the outer control ring.

The outer ring can't usually be connected to the iris direct as the lens expands and contracts as it focuses, and often makers add a spring to the iris to act as a return pressure to open the iris quickly. A lever or prong will connect the iris ring to the outer ring.

This means the ring around the iris must be clean and the spring working properly. Topcon may have not used a spring, some makers did not, but it makes the inner ring even more vital to be cleaned from and dirt and dust. Spring versions give no back lash, prongs give slight play, but means the operation is lighter on the camera iris control.

As Mickey has said, use lighter fluid to clean, add drops with brush and used cotton buds to remove excess and the dirt. If it is a sprung iris it should be able to flick open and closed after cleaning, if it is a prong a second ring drives the iris open and closed.

I have described the parts as rings, but these may be half rings or even levers and cams, but the operation is the same. Wear and tear is almost unknown in quality lenses, it is almost always dirt and oil that are behind the problems.

Stephen.