L39-NEX adapter mod for infinity lock pin

Started Jan 14, 2012 | Discussions thread
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ericdfw
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L39-NEX adapter mod for infinity lock pin
Jan 14, 2012

I remember reading something about this a while back, but couldn't find good images on the topic.

I bought an Industar-22 collapsible lens recently, along with a RainbowImaging L39-NEX adapter. Like many rangefinder lenses of its era, the Industar has an infinity lock tab/pin. You can screw the lens on to the adapter, but you can't fully focus - either you leave it at infinity, or you disengage the lock before attaching to the adapter, in which case you can't move it back to inifinity focus. It is a mechanical fouling condition. You can see the infinity lock pin clearly below (off-topic, but yes, that's an o-ring around the collapsible barrel - necessary if you don't want the lens to bottom out against the camera body - it wouldn't actually hit the sensor, just the plastic around it in the body recess, but still seemed like a bad idea).

I read one option is to first adapt the lens to Leica M-mount, because the M-mount to NEX adapters have a recess built in. Well, I didn't want to buy another adapter (have too many varieties as it is), and really didn't want to alter the lens, even something as simple as removing the spring/pin. Since the adapter is really cheap, I had no qualms about going at it with a grinder. First, I removed the 3 screws that hold the silver threaded piece to the adapter. Before taking that threaded piece off, I played with rotating it around (with lens attached) to mark where I'd want to grind a relief. The main adapter body is clocked only one way when attached to the NEX, so this step lets you decide how your lens will be clocked when mounted.

A few minutes with a drill-mounted grinding bit, then a good cleanup, quick touch-up paint, then reassembly, and I have a pretty decent looking adapter that is fully compatible with the locking pin.

Picture taken with the NEX 30mm macro, by the way. I like this lens for macro shots like this - no frightened insects to worry about here.

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