What's this thing for?

[revdocjim]

The revolving back on my Wista 45N has a small tubular shaped protrusion on the bottom right corner that is threaded on the inside. Can someone tell me what it's for.

It's visible in the bottom left of this photo.
http://chemicalcameras.files.wordpress.com/2010/11/dsc028641.jpg

[aduncanson]

Wista technical cameras offer what they call an "Auto Eye Mechanism" with the Wista S shutters. The shutter closes when a film holder is slid into position. This is accomplished with an "automatic interlock release" (looks like a double ended cable release) connecting that fitting to a special socket on the shutter.

[revdocjim]

Ah hah! That would explain the second socket on the two Wista shutters I have including the one pictured. Interestingly, when I screw in a cable release to that second fitting, depressing the release opens the shutter and aperture blades rather than closing them. So I'm not sure how the whole thing would actually work in real life...

And I guess I'm still wondering about the purpose of the "Auto Eye Mechanism". Is it simply to save you the labor of closing the shutter yourself when you insert the film holder? That seems like such a simple task. It almost seems like hooking up an extra cable would be more work, unless you are taking lots and lots of frames in one outing.

[aduncanson]

It is also designed to work with the sliding roll film adapter, very much a production oriented accessory.

[Sascha Welter]

Sinars have a similar mechanism. We learned not to trust that mechanism back then, back where I worked :-)