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Lens and Optics
Jupiter-12 Lens Dismantle and Clean

Rev.1

The following describes the steps to dismantle and clean a Kiev mount Jupiter-12 lens.

 

First thing you have to do is remove that big hunk of glass that is just begging to be scratched. Get one of these handy rubber mats that are intended for use in the kitchen for aiding in twisting off stubborn jam jar lids. This makes the initial start to undoing this threaded lens element just so much easier.

 

Continue unthreading and put this lens element in a safe place, away from accidental brushes with danger. I can't say enough about this.

 

Push the spring for the collar base aside to enable the removal the grub screw.

 

Remove the front lens block by placing your spanner on the two innermost slots.

 

Here's a closer look at the two inner spanner slots just to highlight it.

 

The whole front lens block just removes as an assembly. Place aside in a safe place.

 

Place spanner on the outer slots to remove the lens block aperture selector.

 

Unthread completely to remove the aperture selector.

 

Make note of the spacer shim used to set the proper lens offset. When it is time to play around with setting the working distance of the lens this shim will be increased or decreased as needed.

 

If your aperture selector is stiff it is likely caused by this congealed grease that over the years takes on the consistency of cross-country ski wax. Thick and sticky. Scrape as much of this away as you can.

 

Remove this screw that engages the front collar/aperture selector with the aperture mechanism itself.

 

Unthread the front collar from the aperture base to reveal the extent of the congealed grease. Elsewhere in these procedural documents I have advocated using Acetone as a cleaning agent but I am finding that Lacquer Thinner really cuts through this old grease better.

 

After you have cleaned up all the old grease use a well dampened non-creeping grease to make the aperture turn nice and smooth but with a little resistance. Nothing worse than an aperture ring that turns too freely. You will forever be aggravated by an aperture ring that bumps off the selected aperture setting by just merely moving the camera around.

 

I find this grease to be good for such uses. It will not creep or flow. I did this test several months ago where I placed a dollop of grease on a sheet of glass and left it. Here are the results. No slumping or running of the grease. There are several special dampened helical greases available if that is to your preference.

 

Reassembly is the reverse of the previous steps. Just a few words though on a couple of the reassembly steps. When you thread the aperture collar back onto the base, the screw stop indicated by Yellow Arrow should just catch the slot. As an aside, you can only have the aperture collar threaded on in full turn increments such that the little dot will align with the aperture numbers as shown by Blue Arrow.

 

Blow off any dust with a can of compressed air and clean the optics with a good approved cleaning system prior to final assembly

 

If you feel the need to clean between the two lenses of the front group they unscrew apart.

 

You now have access to clean between these.

If the focus movement is not stiff you may complete the reassembly and proceed to: Checking Lens Working Distance to finish off.

 

Stiff Focus Movement

If the focus movement is stiff it is probably from the old grease breaking down into a congealed mess of sticky goo. Not a problem, a few more steps are required to remedy this if you have already have your J-12 apart this far.

Remove this threaded collar. You'll need a long spanner extension to get down inside there to get at this one. Before I had the long extensions to my spanner I used a soft brass punch and drove the end point against the spanner slots. Sort of crude but it worked.

 

Loosen the three set screws around the perimeter of the focus ring.

 

Lift the focus ring away from the lens body.

 

Turn the focus all the way to the infinity setting and scribe a little mark on the black body that aligns to the infinity mark. This will aid in placing the focus ring back to correspond with the actual helical position.

 

Remove the three little set screws around the perimeter of the lower lens body collar.

 

Lift the lower lens body collar away from the lens mount block.

Make note of how the scribe mark you made that indicates the infinity mark aligns with the right hand end of the big lobe on the spring collar.

 

Take out the two stop screws for the spring collar.

 

Remove the spring collar from the assembly.

 

Scribe a mark to keep track of the extent of rotation of the focus movement at the infinity position. When you remove the focus rotation stop screw this will indicate the maximum rotation of the focus movement.

 

Remove the focus rotation stop screw.

 

Start unthreading the helical. Just at the point where the helical threads disengage, scribe a mark as indicated so that you know where the re-entry point of the threads are.

 

Clean up the old grease and relube the helical threads with the same grease mentioned earlier. You are now set to re-assemble the lens focus in the reverse order making note of any scribed marks to help relocate the position of items. Your lens focus movement should now be silky smooth.

 

 

June 05, 2006