View Full Version : Inexpensive Gerogon Shutter Installation

Ed Balko
20-Mar-2002, 20:31
I recently bought a 240mm f9 APO-Gerogon. It was quite a bargain at $23, apparen tly new and unused - it was still in original packaging.

I've fitted it into an Elgeet No. 3X shutter. This is a self-cocking shutter ori ginally used on an oscilloscope camera. The Elgeet came with the original 75 mm lens still installed; the 75mm doesn't cover 4x5 so I seem to have gained a pair of paperweights here. The Elgeet shutter has a speed range of 1-1/100th second and I use the "T" setting for focussing.

The Gerogon design has the mounting ring it its center with the optical elements protruding out from both sides of the flange. The metric threads on this lens d id not match the 1.75"-44tpi threads on the shutter so I chose to mount the shut ter at the rear of the lens. Steve Grimes website has a useful discussion on th is type of mounting.

To mount this lens I machined a short lens barrel 1" long and with an internal d iameter a bit over 2", just enough to allow the rear element group to slide free ly into the barrel. The Gerogon required a depth of 7/8" to accomodate the rear element group; the original flange was then mounted to the end of the barrel.

I machined a short threaded portion on the end of the barrel to screw into the E lgeet. Interestingly, there seems to be some variation in the thread dimensions of the Elgeet shutters. The treads which I cut on the barrel end were a good fit for the shutter which I used and also fit well into a Graflex Speed-O-Graph shu tter which I also have. These threads were too small for a second Elgeet which I tried - I'd estimate that a 1.77-44tpi male thread will be required when I even tually fit a lens to the second Elgeet shutter.

I'm using the Gerogon on a older Calumet (C-400?) view camera. There is no vigne tting with the front standard in the full fall position or at either full slide position. I do see some vignetting with the standard at ful l rise (about 2 1/2" on this camera), not unexpected with a rear shutter. There is a full image at 2" rise and I'm prepared to accept the 1/2" loss of front ver tical displacement. I removed the iris from the Elgeet in order to minimize obst ruction of the image path through the shutter; this is no loss as I'm using the diaphragm in the Gerogon which of course is already calibrated to the lens.

I've also fitted a 13" f10 APO-Raptar to the Speedi-O-Graph shutter. The rear el ements on this lens protrude 5/8" behind the flange and I was able to mount the lens in a 3/4" long barrel. The mounting ring threads were 30 tpi , a pitch whic h I can't cut on the lathe which I use, so I again mounted the original flange o n the end of the barrel. The threads which mate with the shutter were also 1.75- 44tpi.

There is no vignetting evident with the Raptar even with full front standard ris e. I presume that this is a consequence of the greater prjection distance of the longer focal length Raptar. I left the iris in the Speedi-O-Graph shutter as it retracted fully into the shutter and did not present an light path obstruction.

The modest price of the Speedi-O-Graph an Elgeet shutters, $30-50, makes this ty pe of installation an attractive proposition. The Gerogon also seem to be availa ble at quite a low price.

Jim Galli
21-Mar-2002, 23:09
Hi Ed. Here's another one (shutter) and I linked it to your thread! http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1341149135

Leonard Robertson
22-Mar-2002, 13:48
Ed - That's a great idea to mount the lens flange to the front of the barrel. I'm finally getting so I can (sometimes) cut a reasonably smooth external thread in aluminum on my South Bend, but internal threads are beyond me. I'm going to try your idea on a 12" RD Artar I have. Anyone interested in front mounting barrel lenses might try to find the March 1980 issue of "Modern Photography" (library or eBay). There is quite a good article which includes thread specs for #3, #4, and #5 Ilex and #4 Compound shutters. Somewhere I have an article on making a "thread duplicator" attachment for the lathe, so threads of any tpi can be cut. It looks like the perfect thing to be able to cut all the odd pitch threads found in camera equipment. What aluminum alloy do you find works best for threading, and are you using HHS tools?