Cleaning LEICA ELMAR 9cm (90mm) f4 aperture blades and aperture mechanism

Here’s a guide on how to take apart the LEICA ELMAR 9cm f4 and clean its aperture blades and aperture mechanism.

First, un-thread the optical assembly on top from the larger focusing helicoid body.

The optical assembly that houses the aperture ring and blades. Un-thread it from the main focusing helicoid body.

Then you need to remove the front optical element. You can use the appropriate rubber spanner tool (a single tool can be found on ebay pretty cheap, a set costs more), I’ve also read of people using a rubber mat cutout (e.g. from a mousepad) and rubber door stopper bumper. In my case, it was enough to pull a rubber band (once held a bunch or parsley together) over the edge of the top element and twist hard. Whatever you use, ideally make sure nothing touches the glass element. Here’s an interesting AMA on reddit with a camera repair technician with some details on how to open lenses.

Take off the front lens element. I used a rubber band around the outside of the filter housing and had to twist hard. The aperture ring also holds two small screws to fix the aperture ring to the internal blades.

Open the aperture blades all the way to f4 now before you take off the aperture ring.

Next, remove the two little screws on either side of the aperture ring (see above as well). They thread into the aperture ring, going through a brass glide bushing, long cutout slots in the lens barrel and into two holes on the aperture blade “driver” that positions and moves the aperture rings inside the lens.

With the top optical element and screws removed, you can now un-thread the aperture ring and when it spins freely you can carefully pull it out over the top.

I forgot to take pictures of the aperture ring “driver”/retainer inside the lens. It’s a black metal ring with slots that the aperture blade pins are slotted into. When the “driver” rotates, the blade pins change position and close the aperture. Take not of where the two small holes on the aperture driver are, otherwise you’ll need to reverse-engineer the exact position later — not a big deal noting the position makes reassembly easier.

You can clean your aperture blades now. I used 92% isopropyl alcohol which I had on hand — I also saw naphtha lighter fluid recommended often, please do your own research and decide for yourself. I found it useful to bath them in a film container for a bit, carefully agitating.

Also clean all threads on the outside and inside of the lens now, make sure you got all the grease and oil out before you reinsert the aperture blades.

I found it useful to clean aperture blades in an old film container.

Reassembly.

I am not sure what the right way is to reassemble the aperture blades, here’s what worked for me but there is probably a better way.

First off, the blades have a smoothly rounded end and an end that’s not perfectly round. The pins on the rounded end go into the holes in the lens body, the other pins into the aperture “driver” ring. See photo below.

When it came to insert the last few blades that go under the first blades, I used tweezers to carefully lift some of the blades. So I started positioning the first blade so that its non-round end was just before the cutout on one side of the barrel, worked my way around and then lifted the blades when I had to insert the last blades under the first ones.

The internal black brass aperture “driver”/ring may be self-lubricating and not need lubrication but the reason I took the lens apart in the first place was because the aperture was hard to adjust. So I carefully lubricated the outside with a light grease (this thread seems to suggest that LEICA recommends vaseline/petroleum jelly on recent lenses) . After lubricating, make sure you clean the top and bottom of the ring with a Q-Tip and alcohol so that the grease won’t get on the aperture blades! Using the wrong lubricant may damage your optical lens elements/coatings when compounds evaporate so be careful.

Now recall the position of the holes in the aperture “driver” noted before and position the ring in the same way. Carefully lower the aperture “driver” onto the blades, roughly lining up the pins with the slots. Then you need to carefully adjust each pin to fit into the slots. When everything lines up, carefully apply pressure on the ring and adjust any pins that may still not quite fit. Make sure the ring now snuggly fits and you can see the its two holes through the guide slots on the lens barrel.

Lube the outside threads, brass glide bushing threads on the aperture adjuster ring as you deem necessary. Make sure the two holes on the glide ring align with the holes on the aperture ring. Carefully lower the aperture adjuster onto the lens barrel. I next threaded the adjuster all the way in carefully until it bottomed, then backed it out about half a turn until the holes on the adjuster and glide ring aligned with the holes on the internal aperture blade “driver”. If your glide ring moves when turn the aperture adjuster ring you need to stabilize it somehow — I inserted on of the screws to keep glide ring and aperture ring holes aligned. When all the holes are aligned and you can see some light shine through the aperture ring holes, insert the two screws again and tighten them carefully. Make sure your aperture ring adjusts the blades and is correctly opening and closing the blades, also make sure that open/closed aperture correspond to the scale on the body.

Thread the top element back in and tighten with your rubber band or tools. Thread the optical assembly back onto the focusing body and you should be done.