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,
- 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
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.
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.