Inexpensive Gerogon Shutter Installationgreenspun.com : LUSENET : Large format photography : One Thread
I recently bought a 240mm f9 APO-Gerogon. It was quite a bargain at $23, apparently 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 originally 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 did not match the 1.75"-44tpi threads on the shutter so I chose to mount the shutter at the rear of the lens. Steve Grimes website has a useful discussion on this type of mounting.
To mount this lens I machined a short lens barrel 1" long and with an internal diameter a bit over 2", just enough to allow the rear element group to slide freely 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 Elgeet. 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 shutter 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 eventually fit a lens to the second Elgeet shutter.
I'm using the Gerogon on a older Calumet (C-400?) view camera. There is no vignetting with the front standard in the full fall position or at either full slide position. I do see some vignetting with the standard at full 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 vertical displacement. I removed the iris from the Elgeet in order to minimize obstruction 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 elements 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 which I can't cut on the lathe which I use, so I again mounted the original flange on 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 rise. 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 type of installation an attractive proposition. The Gerogon also seem to be available at quite a low price.
-- Ed Balko (firstname.lastname@example.org), March 20, 2002
Hi Ed. Here's another one (shutter) and I linked it to your thread! http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1341149135
-- Jim Galli (email@example.com), March 21, 2002.
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?
-- Leonard Robertson (firstname.lastname@example.org), March 22, 2002.