It was an early Christmas for me and I acquired two interesting lenses.
The Dallmeyer Triple Achromat #1 is a lens from 1863, yes, 150 years old at time of writing and still in perfect shape. Three achromat lenses, two positive with the middle one negative. A sharp and quite popular lens for the days, only replaced when the rectilinears came out in 1866 and later.
When one removes the inner negative achromat, the back focus is halved (from 7" to 3.5") and the f# almost doubles. As a bonus, one gains a "soft focus" effect in the process. This also meant a little challenge on mounting this lens for optimum dual use. (The "soft focus" feature was disclosed by Dallmeyer himself in 1861.)
The image below shows the solution I came up with. The lens is mounted normally on a few macro extensions and I used this time a macro reverse adaptor with a 67-77mm lens-filter adapter and a metal 77mm lens cap to mount the lens on. This gave me perfect infinity focus with this set-up. Pricier than using the plastic body cap but this method maintains an all-metal construction and the assembly allows for infinite focus for this particular set-up either way.
With the middle element removed, the back focus is too short to be used with this camera set-up. So, I came up with a way to reverse mount the lens and get the necessary minimum clearance (in the helicoid) to achieve infinity focus again. See the middle image. With the lens reversed, the soft focus effect remains intact and there's sufficient coverage for 645 and 67 style medium frame cameras.
The lens at right shows the Karl Struss Pictorial lens mounted on three macro extensions. The helicoid removed is removed. Incidentally, the #1, #2 and #3 macro extensions were needed. I used the "standard" plastic body cap mount for the lens. This is the 9" version intended for Graflex camera use. The lens element extends quite a bit inside. This way the Graflex camera could be closed without removing the lens.
This particular Karl Struss lens in this configuration is not extendable/collapsable. There was a version on the market for short bellows Graflex cameras with a collapse feature. Once the bellows were extended over the bed, the lens could be pulled forward and would extend all the way out.
Pictures taken with these lenses in the near future.
Enjoy ... happy Holidays !