I had Canal Plastics Center ( www.canalplasticscenter.com/index2.shtml ) laser-cut some squares of black perspex, 1/4" x 85.1mm square, along with a central laser-cut hole. They do it while you wait (30 minutes), and cost $6 each. It sits snugly inside the inner lip. The brass pieces that go over the inner lip and under the lensboard retainers are cut from 1/32" x 3/8" brass strips from Pearl Paint, attached with 2-56 machine screws and nuts from the hardware store. The corners of the perspex are rounded by rubbing against sandpaper.
Pic 1 is an ancient 110/7.7 Dagor.
Pic 2 is an 85/2 Jupiter-9 experiment...illumination circle is 3.25". Am thinking of getting a Baby Speed for it.
My implementation of an idea I saw on one of the forums: Having only two hands I found it extremely hard (no, impossible) to simultaneously hold and aim the camera, hold the loupe in place, and work the focus knob. Solution: A 1/8" black perspex ground glass protector velcro'd to the focus panel (nothing new so far) with a central hole drilled just large enough for a loupe. The loupe fits snugly enough that it will stay in place while focusing. I added a couple of velcro tabs for added security. The loupe is removed when tossing the camera into the bag so as not to break the glass. The loupe is made from a plastic film can and the back cell of an unknown Wollensak lens in Betax No. 2, probably a Tessar-type, that was missing its front cell. A hole was cut in the closed end and the open end cut to length for focus.
