Modifying the Leica Super Angulon f3.4

Not for the Faint-Hearted.

Synopsis

The f3.4 Super Angulon can be made to work with the light meter on the M6 body. This process involves "machining" the rear collar of the lens (though it can be done with simple tools, outside of a machine shop).

    • It is assumed that you are ready to dismantle and modify your lens.
    • The meter will read 1/3 stop under, which is compensated for by advancing the film speed dial by one notch.
    • The lens should be focused to close range in order to accurately meter. Close-focusing is needed to nudge the rear glass out of the way of the metering eye, and can be quickly done and then un-done while shooting. (However, on an M6 with the spot size reduced for tighter metering pattern, this close-focusing has been found to be unnecessary.)


OUTLINE:

The basic steps are: Removal of the rear cluster from the lens, removal of the two element groups from inside the rear collar, cutting a shallow notch in each of the rear collar and rear mounting ring, re-assembly of the two element groups, and replacement of the rear cluster.

REQUIRED TOOLS & PARTS:

The following tools are required for this process:

    • Wrench, lens spanner, small
    • Wrench, lens spanner, tiny
    • Duster, compressed air
    • Cloth, lens cleaning
    • Shutter release cable
    • Body, M6
    • Prying object, soft, small, such as toothpick, nylon pick, etc
    • File, blunt-round, small

STEP 1 - MARKING

Ensure that the rear cluster on the lens is firmly screwed in place. It tightens in a CW direction, and should be firmly secured before beginning. There is no need to over-tighten this part. Simply check it at this time.

Remove the base plate of the M6. Remove the film back (release tab is a small screw head at the upper-left corner of the back). Attatch the release cable to the trigger. Set the shutter to "B" and hold open with the release cable. Mount the lens. Focus the lens to its closest setting (40 cm). Looking through the back of the camera, observe the metering eye and its angle of view to the rear collar of the lens. If you have the latest Super Angulon, you will be able to see the obstruction of the metering eye by the rear collar. With the rear collar notched just below the metering eye, the eye will have visibility to the shutter curtain spot. There will remain a thin obstruction by the rear glass, which will cause a 1/3 stop loss in metering. (This will be compensated for with the film speed dial.)

Use the felt tip marker to mark the segment to be notched at the edge of the rear collar. I removed a segment apx 1 cm long, thus providing a wide flange of visibility on either side of the eye. There should be some degree of side-to-side margin in your notch, as the rear collar will turn when it is removed. Also mark the rear mounting ring, which is the threaded ring situated between the outer collar and the glass.

STEP 2 - CLUSTER REMOVAL

Remove the lens from the M6. Check that your marks will withstand handling and touch-up if needed. The marks only need to indicate the area of the rear collar to be notched. That is, the length of the segment to be removed, not the depth.

Using hands only, unscrew the rear cluster from the lens. It will unscrew in a CCW direction. Place the lens body off to one side in a well-protected area.

STEP 3 - GLASS REMOVAL

Adjust the small lens spanner wrench to the size needed to remove the rear threaded ring. Remove the ring in CCW direction.

Use a nylon pick to gently pry the edges of the rear element until it is easily removed. It should drop out of the cluster. Place it to one side in a well-protected area.

Adjust the tiny lens spanner wrench to the size needed to remove the threaded ring located in the barrel of the rear cluster. The ring will unscrew in CCW direction. Gently press the protruding glass element against a soft surface and it should drop out of the rear cluster. Place the element group and the smaller threaded ring aside in a well-protected area.

STEP 4 - NOTCHING THE COLLAR

At this point, there is no glass in the rear cluster. Use the file to notch the edge of the rear collar to your previous markings. The notch to be removed should be as described: circumferencial length: apx 1 cm depth: apx 4 mm, no further than inner shoulder. Inner corners: round. Outer corners: round.

The depth of the notch will expose the edge of the rear glass element. This is intentional, as the eye will then only be limited by the edge of the glass. Make sure to provide round corners at the ends of the notch. These prevent snags with things like coats, shirts, etc, and will reduce cloth burrs during lens use.

When the notch is complete, take a few moments to gently finish all edges with slight de-burring.

STEP 5 - NOTCHING THE THREADED RING

The same notch that was made in the collar must also be made in the threaded ring that secures the rear glass. The notch is made according to the prior marks so that when the ring is re-mounted, the two notches will line-up. Making this notch is a bit tricky, as there is very little material remaining when the notch is deep enough to just barely skim the surface of the glass. I would highly reccommend leaving some amount of material (as opposed to removing all material and transforming the ring into a 'C' shape). With no material left, it is likely that the ring would collapse when tightened in the threaded barrel and would not stay mounted. What I did was to bevel the floor of the notch here so that the notch is deeper on the outside of the ring. If you work slowly, you will see that there is an optimum shape for the notch floor that leaves most of the remaining material outside of the glass, closer to the threads. I left the full width of the remaining material but the thickness over the glass is perhaps just less than 1 mm. Not much is needed, as the ring is only mounted with a limited amount of torque.

STEP 6 - BLACKING METAL PARTS

Now that there is bare metal in direct view of the metering eye, this step applies black coating to help cut possible close reflections.

At first I did this with black paint, but the proper way is to use black anodizing treatment, which doesn't add dimensional change and is more robust in handling. This finish is for either brass or aluminum, and you can find it at www.fargo-ent.com.

STEP 7 - CLEANING

Before any re-assembly of the glass, I would highly reccommend cleaning. A compressed air can should be used to blow out the iris cavity. Be sure to test the air jet first to insure that it does not stain glass surfaces (If it does, this will be obvious - it has to do with cold liquid in the feed. Usually a few pre- puffs will clear it up). Also be sure not to blow hard on the iris if it is closed.

Some very light buffing might also be applied to either glass surface which faces the iris. This can be helpful if you can see fogging under bright pinpoint lighting against a dark background, and will most likely occurr on these two inner surfaces. The forward surface may be difficult to access without removal of the front assembly. I wouldn't do this without isopropyl alcohol, denatured alcohol would also work.

If you decide to remove the front elements, here's a hint: After you have unscrewed the front cluster of parts from the lens body, you will need to remove the front ring in order to take out any glass. But the front ring will not unscrew until you first remove the tiny set screw on the side of the ring. - then you can unscrw the front ring.

STEP 8 - REAR CLUSTER RE-ASSEMBLY

The rear collar glass is re-assembled in the same steps used to dismantle it.

STEP 9 - [OPTIONAL] GLASS MASKING

When fully opened, the Super Angulon may (depending on version / vintage) show a slight halo of light surrounding the iris. This is caused by un-masked glass at the inner-most part of the rear cluster and can be fixed quite easily. The inner-most element is attatched to the next with cement only. It is not held by a collar. Many of the Super Angulons have nothing to block light from going through the fringes of the cement mount.

Locate the inner-most element, which is distinguished by its obvious protrusion at the iris end of the rear cluster. The same black-out paint can be applied in the slot surrounding this element in order to fix the halo problem. Note that this should be done only with the rear glass installed, as proper seating of the glass is only possible when bare glass contacts the mounting collar. Once this paint is installed, it will be a little more difficult to tap the glass free if it is to be dismantled again (but it's been at least 25 years already...).

STEP 10 - COMPLETION

The rear cluster may be re-mounted once all paint has dried. If you have blacked-out the inner halo slot, this must be given a thorough drying time - like a full day so the paint can outgas.

With the lens re-assembled and mounted to the camera, the film speed dial will be set forward by 1 notch ( 1/3 stop ) in order to compensate for a minor eye obstruction by the glass. When the lens is focused to the close settings, the metering is accurate. If metering is attempted with the lens focused to infinity, there will be an additional ~~ 2/3 stop error.

SPOT METERING

To reduce / remove the metering error, the metering spot can be halved in area. This allows the metering eye to ignore the fringe parts of the spot, part of which is blocked at distant focus settings. A tighter spot results in a more concentrated area for the eye to see which is less effected by focus setting. The metering eye can always see the center of the spot, so why not just use that? With a spot 1 stop smaller, my Super Angulon meters consistantly throughout the entire low half of the focus range, and then only begins to loose 1/2 stop at the very distant end, as the glass nudges up close to the film plane.


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