Angenieux 10-150 repair

Robert Hart · June 3, 2017

As with any older standard 16mm lenses, if they go faulty, they may be assessed as uneconomic to repair. Hence I have been compelled a few times to repair my own.

I have an old 10-150 that came with a CP16R camera years ago. I had it professionally repaired for a separated element about 1993. The repairman enquired if I wanted him to split the remaining optics, clean and reassemble them with the then revolutionary UV-cure optical cement.

Thank goodness I did not because the element which was repaired with UV cure is beginning to become a little smokey with some sort of crystalline deterioration. After having the lens stored for some years, I bought a PL-Mount from Ken Hale at Whitehouse AV and fitted it.

Unknown to me was that the iris blades must have had some stray oil creep onto them and within a few hours of use on a SI2K camera, I observed a weird bokeh. On a closer look I saw that the iris blades had gone goats eye in a sort of an onion shape.

I took it apart and found four blades were damaged, one snapped and three with their pivot pillars stretched out of their holes. After a few years of looking at it, looking on the net for parts and putting it away again, I finally found that Pillefilm in Europe had some blades.

They are not cheap but given the difficulty in making them, that is to be expected. I know they are difficult because I made one. I bought in five from Pillefilm and set about re-assembling the iris cell. Iris blades are the devil's own concoction to fit. There is a method which is the direct opposite to the assembly sequence one would expect.

To stop them from sliding around all over the place in the final assembly of four blades, I found that placing the cell on a business card sized fridge magnet sign, that they were immobilised sufficiently but still could be moved when needed. Maybe that's how they do it in the factory. I don't know. The blades appear to have been stamped or cut from fine steel or spring steel shim metal.

My question to anyone who can advise is, can I expect any issues from the iris blades becoming magnetised? Maybe it might help keep them together. Maybe magnetic attraction will provoke more friction and more problems.

Any advice appreciated.

Simon Wyss · June 3, 2017

Yeah, magnetic leaves you don’t want.

Methods are different with lens manufacturers. The iris cage is arrested, mechanically, not magnetically, often on a rubber or plastic socket or similar. An aid with springy leaves is used, plastic in many cases or from bronze, to hold down the iris under assembly. When complete, the leaves are swung together and secured with a little weight, if not mounted right away. It’s about avoiding dust and grease and everything.

Larger iris leaves are made with non-smooth surfaces. Good iris mechanics are key to good lenses. Unfortunately second-class diaphragms have been found with a number of products, I know of some amateur mass products that hardly justify a repair job. What’s in a name? Wollensak made bad irises, Berthiot made bad irises. TTH has made little tubes for pivots. Zeiss has sturdy bolts. Kinoptik has solid bolts. Sometimes grooves are not up to snuff.

Dom Jaeger · June 3, 2017

It usually takes stroking a metallic object many times with a magnet in one direction to magnetise them, I doubt the iris blades will have magnetised much at all just having been held temporarily by a weak fridge magnet. Even if there was some magnetism passed on, it will dissipate quickly with time.

I find patience and tweezers to be the best method for iris assembly, occasionally I'll use a slight weight applied to keep the already fitted blades in place, being careful not to bend blades that are resting on pivots. It's something you get better at with practice.

Oil gets onto the iris blades from grease separation, so avoid using grease anywhere in the iris assembly.

Robert Hart · June 4, 2017

The oil on the iris leaves on my lens was plain stupid carelessness on my part, grabbing a lens out of long storage, taking off the CP-Mount, shoving on the PL-Mount, shimming it to infinity-focus and straightaway using it.

If I had bothered to just look, I would have seen that something had got on the leaves from somewhere inside.

With the iris leaves, the big challenge was getting the last four in because the first has to be slightly raised for the last leaves to be inserted beneath and registered into their pivots.

As a lens, the 10-150 is not all that good, softer with a warm cast compared to the 12-120 which was on the older CP16 non-reflex camera. It works well enough now. I just have to get that rear optical group centred, which is a tiresome but essential business.

I have a lot of respect for the people who make those iris leaves. I know there is developed craft and methods to make it easier. Cutting one out by hand from shim metal was a real challenge. It is not impossible but very, very difficult.

I have an old Cine-Zenon 28mm f2.8, which is also goat-eyed from misadjustment of the mechanism and overclosing of the iris. Those old lenses have only five iris blades.

One has a cut-out to enable assembly. That leaf is extremely fragile as the cutout leaves only about 1mm of metal.