Kodak Type M Cine Lens Adapter for MFT Cameras

I didn't know of any available adapters for these unusual lenses, so here one is!

The smart little Kodak Cine-Ektar 25mm f/1.9 is the only one I have tried, but the coverage on a Four Thirds sensor is pretty good and it is quite usable. I expect the telephoto types have at least as good or better coverage.

It's designed for the lens to friction fit snugly - not so tight that it can't be moved but not loose enough so it falls out.

Thanks to Ferdinand for the original Nikon F mount design I made this from. Aside from butchering this model for my own, I made a small change for a tighter fit on the MFT mount locking pin, as well as a small notch to assist with locating the adapter with the red dot on the camera body.

This adapter is not compatible with the similar C mount versions of these Kodak lenses.

Variants

There are two types here - one with a more grippy rim that can be easier to mount on the camera, and one with a conical rim that gives slightly better finger access to the base of the lens barrel when twisting to insert or remove from the adapter.

Adjustments

Back Focus

The design is made to achieve infinity focus reasonably well on the barrel marking, but of course there will be some variation with different camera bodies, printer, filament, slicer settings etc.

If, after printing, you think your lens is focusing past infinity, then you can check the amount you need to correct for by:

- Find infinity visually in camera with a far-away object and lens wide open - Measure the barrel extension with vernier calipers or micrometer - Set lens to infinity mark - Measure again. The required offset is the difference between the two measurements. If it's not focusing far enough to infinity, then try nudging the lens out of the adapter and measuring the gap with a feeler gauge for when you get infinity focus at the barrel mark.

Back focus adjustment can be made using the supplied .3mf file - move the internal mount part up or down by the offset you need and then slice.

Alternatively, you could shim the lens and carve out some of the internal tracks, but I reckon that could introduce more inaccuracy (possible tilt, etc.)

Tightness of Lens Fit

I have found that PETG comes out noticeably tighter for the internal (adapted) lens fit - so much so that it can be very hard to pull out. There is a cylindrical negative volume on each model ("I.D. Adjuster") in the .3mf which can be sized up to allow for a workable fit. I have found that 28.8mm is good for PETG.

Printing Notes

These guidelines are also described and followed in the .3mf file:

- Print front-down (original model orientation.) - Add supports for the two internal bayonet tracks and the top three MFT mount flanges. - PLA with 0.2mm layers should work well with no adjustments with the included models. - Two-colour prints can look good, as long as you change the colour to black for the sensor-facing part (start at 9mm height on model. - PETG printing - see above section.