Bolex H16 lens question

Tim Halloran · November 14, 2009

Hey guys,

Is a zoom like the Vario-Switar 86-OE (18mm-86mm f/2.5) lens compatible with an early H16 REX (I think commonly referred to, or known, as a "REX 1")? I don't know why it wouldn't be but my girlfriend popped up with the comment that she thinks those zooms only work with the REX 4 or 5.

I tried going through every bit of Bolex data I could find to confirm either way and couldn't find anything definitive. Nothing really on the bolex collector site or Alden's page. Only thing that I found which might support her claim is from Lenny's Independent Filmmaking:

"Model H-16 Rex 4 and 5...have reflex viewing and focusing through a behind-the-lens beam splitter. Fixed focal length lenses from 10 to 50 mm, and zoom lenses are specially adjusted for the 4 and 5 bodies, because of the beam splitter[italics mine]. These lenses are marked 'Rx'."

Makes sense except that I think the lenses on my REX 1 are also 'Rx" lenses, so I'm confused. I bought this camera a couple of years ago and am just now getting it ready for use. I'm still learning all of the details so forgive my ignorance of some of the basics.

Still, the primary question: will the Vario-Switar 86-OE work with the REX? :)

Any help or suggestions?

Tim

Bernie O'Doherty · November 15, 2009

Tim, you'll know it when a lens is not configured for your Bolex. It will either not focus properly, or, in the case of a zoom, it won't hold focus throughout the zoom range. When it doesn't look good, it's probably non-rx, meaning it's set up for regular "c" mount distance:17.52mm.

A Bolex Rx mount, on the other hand is set-up for a flange focal distance of 20.76mm. This longer distance is because the prism in the Bolex light path pulls the light rays further back into the camera.

This is the reason people unscrew a non-rx mount farther out in order to attain focus. A shim in the lens mount will also bring you into proper focus. Sometimes you will have softness in the edges when interchanging rx and non-rx lenses. It depends on the lens design and the angle and size of the exit pupil.

If you don't see that softness by eye, a film test will do the trick.