Carl Zeiss Jena Flektogon 20 mm f/ 4 Lens Manual
approximately flush with the top of the focusing assembly), and then you continue unthreading the focus
assembly from the release assembly. So, two sets of threads were unscrewing, and then just one. Even
though the helicals will rethread in many ways, those helicals must go back together with particular threads
meshing with their matching grooves. You’re in for hours of trouble trying to get the helicals back together,
and timed correctly with the focusing mechanism.
assembly from the release assembly. So, two sets of threads were unscrewing, and then just one. Even
though the helicals will rethread in many ways, those helicals must go back together with particular threads
meshing with their matching grooves. You’re in for hours of trouble trying to get the helicals back together,
and timed correctly with the focusing mechanism.
So you separated them anyway. Another spacer ring (silver side to front) will fall out of the focus assembly
if you invert it (likely also important for precise infinity focus later). The shutter release assembly is still
operational. Clean the mechanism and buff the aluminum at this point. Don’t allow any protrusion to catch
while buffing! Cleaning the cocking mechanism leaves it unlubricated and gritty feeling—relube it without
further disassembly by forcing your lube (molykote) in.
if you invert it (likely also important for precise infinity focus later). The shutter release assembly is still
operational. Clean the mechanism and buff the aluminum at this point. Don’t allow any protrusion to catch
while buffing! Cleaning the cocking mechanism leaves it unlubricated and gritty feeling—relube it without
further disassembly by forcing your lube (molykote) in.
As mentioned, the inner aluminum helical will (reverse) screw up and out when it gets flush to the top of
the focusing ring. It can be painful getting it back together, so clean and lube it. After experimenting with
Molykote and graphite I switched to Nyogel 701 which worked pretty well. Probably should use NyoGel
Helical 744 if I had it. The helical will screw back in (with effort and patience, and from the top, not the
bottom). Note that the helical pushes out toward the front of the lens as you turn the lens to closer
distances. On reassembly, the rear of the focus assembly should almost hit its stop in the back of the release
assembly. That’s your best indication you got the appropriate meshing of the helicals.
the focusing ring. It can be painful getting it back together, so clean and lube it. After experimenting with
Molykote and graphite I switched to Nyogel 701 which worked pretty well. Probably should use NyoGel
Helical 744 if I had it. The helical will screw back in (with effort and patience, and from the top, not the
bottom). Note that the helical pushes out toward the front of the lens as you turn the lens to closer
distances. On reassembly, the rear of the focus assembly should almost hit its stop in the back of the release
assembly. That’s your best indication you got the appropriate meshing of the helicals.
The trick is to set the inner aluminum helicals at a certain point and then use the spanner wrench to hold the
inner helical with its two grooves matching and meshing the upright posts on either side of the inside of the
release assembly, while you turn the outer focusing ring clockwise to screw the helicals on and down. You
can see the rigid posts (at 1 and 7 o’clock) and the rotating aperture cocking post (at rest at 8 o’clock) in the
next photo.
inner helical with its two grooves matching and meshing the upright posts on either side of the inside of the
release assembly, while you turn the outer focusing ring clockwise to screw the helicals on and down. You
can see the rigid posts (at 1 and 7 o’clock) and the rotating aperture cocking post (at rest at 8 o’clock) in the
next photo.
Here’s the trick to reassemble the release and focus units: you have to reassemble the release unit and the
focusing unit WITHOUT the inner aluminum helical tube in place. Screw the focusing unit on all the way
(clockwise) until it stops, and then unscrew it a scootch so the index mark matches infinity. Using this as a
reference point, unscrew the focusing ring one full turn plus a little (go past infinity to the 2.5 meter mark,
which is a point a little more than one full counterclockwise turn from your reference point). Now drop the
helical tube into place, aligning its two grooves so they will mesh with the release unit’s two alignment
posts, and keeping the aperture cocking post within visibility at all times (you can see a special cutout for
its action at the bottom of the helical tube). The helicals are reverse threaded, so nudge them CCW. Just
start to screw the helical into place (a fraction of a turn, just where you hope it will start). Now place your
focusing unit WITHOUT the inner aluminum helical tube in place. Screw the focusing unit on all the way
(clockwise) until it stops, and then unscrew it a scootch so the index mark matches infinity. Using this as a
reference point, unscrew the focusing ring one full turn plus a little (go past infinity to the 2.5 meter mark,
which is a point a little more than one full counterclockwise turn from your reference point). Now drop the
helical tube into place, aligning its two grooves so they will mesh with the release unit’s two alignment
posts, and keeping the aperture cocking post within visibility at all times (you can see a special cutout for
its action at the bottom of the helical tube). The helicals are reverse threaded, so nudge them CCW. Just
start to screw the helical into place (a fraction of a turn, just where you hope it will start). Now place your