making an anamorphic adapter a push-pull focus lens

This is part of the process of building a single-focus anamorphic lens, or accessing the brass plates in order to tune the adapter for maximum sharpness

(1) Check around the front outer ring of the adapter for any set screws that hold it in place.  Loosen or completely remove these.  They can be stubborn.  Use the correct size screwdriver to prevent damaging the screw heads.  If they are impossible to remove they can be carefully drilled out.  If this doesn't fill you with dread you have the personality type for this project.

(2) As per the video above, unscrew the front ring.  This video shows a 35mm adapter, but the principle is identical for 16mm adapters.  I used it for the demo because it's big and it looks awesome.

(3) The focus ring now unscrews and can be taken off via the rear of the adapter.

This reveals a simple push-pull focusing mechanism.  It also reveals that the two lens barrels are held in position by brass plates running in elongated slots.  There will be either 2 or 3 of these.  Often these brass plates have oblong holes underneath the screw heads. This allows the lens barrels to be twisted slightly prior to re-tightening, to facilitate accurate alignment of the barrels (absolutely essential for sharpness).

 

Once the brass plates are unscrewed (2 screws each) the two barrels that make up the adapter can be separated.

 

To allow push-pull focusing the existing grease must often be removed completely as it creates too much drag as well as an airlock that makes moving the barrels quite difficult.  You can see me struggling to move them in the video!  This also imparts too much drag even if the focus ring mechanism is retained, although in the context of using these in front of a projector that didn't matter.

I generally replace this with a very light application of a grease/light oil mix.  If your build alignment is perfect you can get away with no lubrication, which is ideal as the drag is minimised.  

 

MODIFICATION ALERT

I look to create a way for air to be easily moved in and out of the cavity between the front and back lens groups to prevent airlock drag from making focusing stiff.  This could be a groove to the front, or a vent to the side, depends on the adapter design.

© 2020 by mort'mer/mortmer/Bruce Mortimer