Jupiter-12 35mm Contax

J12 Contax Mount



The Jupiter-12 is easily the most popular accessory lens for the Former Soviet Union Leica style rangefinders. They were produced over a period of years in a couple of different factories, this is the later black model from famed Lytkarino (LZOS) factory, who made lenses for KMZ.


The design is such that it’s self-shaded (no hood necessary), and the aperture ring is recessed inside the outer lens housing. Screwing a 40.5mm thread in means that the filter becomes your means for changing aperture.

The most difficult thing with the J12 is protecting the large mushroomlike rear element. It’s well known that minor scratches on the front of a lens have minimal affect on the picture quality; however scratches on the rear element, particularly one that comes as close to the focal plane as this one, are generally obvious on the final image.

Because the rangefinders you will use this on have viewfinders that are designed for the angle of view of 50mm lenses, you will need a special viewfinder to put in the accessory shoe in order to properly frame your subject. Focus in the window as normal, frame in the accesory finder. I use a Petri finder, it’s close enough to 35mm to be very useful. If you have more than one auxiliary lens it’s probably best to get KMZ’s Zeiss copy multi-finder.

Special Notes

Mounting this lens can be a bit tricky. It doesn’t fit in the internal bayonet mount on the camera but the external one that I didn’t even notice was there till I bought the thing.

Kiev 4 J12 Mount

Basically for both removal and install you should have the camera set to infinity. You remove the 50mm lens by locking the focus to infinity, then pressing the lens locking tab and turning the lens clockwise to remove it. That’s the normal, inner bayonet mount. If you’re like me you won’t even have noticed the bayonet tabs outside the lens opening… that’s the outer bayonet mount. Line up the red dots on the lens and camera, press the lens down, and turn it counter-clockwise till it sits. It should be locked in at infinity, test by moving the lens through the focal range, I have to go back and forth all the way a couple of times before it’s in sync. Note that it doesn’t lock at infinity with the J-12; the lens surround has the second locking tab set open. This must be for a reason; I don’t know what it is!

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