From memory, the reflex Standard 8 Nizos use altered D mounts with an extended flange depth, so standard D mounts won't reach infinity, and wide angles will only focus very close.
As far as I know the only reflex Standard 8 cameras that take D mount lenses are the Beaulieu MR8 or TR8 (which use a guillotine mirror like the Nizo) and the reflex models made by another French firm called Christen, which use pellicles.
The camera wouldn’t have the D mount, if lenses weren’t interchangeable. The only limitation can be about the diameter of a lens. The NIzo Reflex uses the same slide mirror shutter as the Beaulieu Reflex and the Ercsam Camex Reflex. There were four mirror reflex shutter 8mm cameras, the fourth being the GDR Pentaflex 8. The Rodenstock came with couplings to the exposure metering system. With other lenses you simply lose the semi-automatism.
It seems reasonable to assume that, but if my memory serves I tried different D mounts in my Nizo Heliomatic Trifo and they didn't focus properly. I think I measured the flange depth and found it deeper than standard. This was about 6 years ago, so maybe I'm misremembering.
But the D mount thread has come with different flange depths over the years. I think I recall one of my my early 16mm Cine Nizos (from the early 30's I think) also used a D mount thread, but with a different flange depth again. Early 8mm cameras like the Bolex L8 from 1942 used a D mount thread with a much shorter flange depth, while the 1938 H8 used standard D mount.
I'm actually curious to know who introduced the D mount standard, it's one of the cine history mysteries I've never solved. Do you know Simon? I'm pretty sure the French firm Emel had a D mount camera out before the Bolex H8, in the mid 30's, but I'm not sure who else may have done so. I also have a vague memory of another 16mm camera using the D mount thread size, maybe a very early single lens Filmo or maybe it was a Filmo 75? But Bell and Howell 8mm cameras used their own special mounts and only switched to D mount when production shifted to Britain in the 50s. Similarly Kodak didn't use D mount for their 8mm cameras until the same era, well after Emel.
Early 8mm cameras like the Bolex L8 from 1942 used a D mount thread with a much shorter flange depth, while the 1938 H8 used standard D mount.
Here we agree, Paillard furnished the according adapter ring after a while. Initially the practice of B. & H. was adopted, a shorter FFD and fitting lenses plus intermediate rings. The American turret 8s don’t have the D-mount thread. Paillard used it.
It looks like the EMEL C 62 of 1933-34 came with the D mount. I haven’t done any research on these, yet. The Bell & Howell Co. had licensed out a number of things that they weren’t allowed to use themselves for the duration of a patent run, 17 years in the U. S. until 1995. Indication of spring tension remaining, clutch between spring and mechanism, reflex viewing such as with the Ciné-Kodak Special, and more. But the most indispensable things were retained. Some things were shared without patent protection, the C mount, the Eyemo mount with the ARRIFLEX (only different dimensions), the tweezers lens lock again with the ARRIFLEX, the critical focuser with Victor (unpatentable), and other ideas.
Bell & Howell’s first 8mm camera, the Filmo Straight Eight, had a clip-on or spigot mount, 1935. The Double Run 8 to follow in 1936 had the same mount. The D mount was introduced with the Filmo 8s from fall 1951 on and it was their only mount since January 1st, 1957. So, by subtracting 17 years from 1951 we are in 1934 or 1933, just about the point in time when a licence to Mr. and Mrs. Grimm could have started.
Same with all other manufacturers, and I don’t think that those licence fees were very high. It was important to keep the game going on, more competition means more business in general. B. & H. had to make as much money and as long as possible out of a few basic principles. The biggest asset was the perforator, then the Standard camera, printers, the Filmo 70, the Eyemo 71, projectors for 16mm film, the 8s.
Thanks, Simon, interesting theory about the patent. It seems to have been a European thing first, with Emel, Nizo and Paillard-Bolex all using it before 1940, although Revere also had a camera from the late 30s with a D mount turret.
You'll enjoy investigating Emel, they are basically miniature Filmos, right down to the sprocket loop and retracting centre rib. It's interesting that Bell and Howell themselves didn't make their 8mm cameras like this.
When I get a chance I'll unearth my Nizo Reflex Heliomatic and check whether another D mount works on it. It's in one of a dozen boxes of cameras in my garage..
You had Bell & Howell competing with Eastman-Kodak for the mass market, the big one. 16mm had become too expensive since fall 1929. Kemco tried their luck. Then the Double-Eight trick was applied. Chicago aimed at the woman, the mother, hence the smallest and lightest 8mm camera for many years. Rochester had envisaged the family father, men. You can also see the difference when you compare a Ciné-Kodak Special to a Filmo 70. The Filmo is more feminine, round, the CKS is an angular block. The Bell & Howell people weren’t always as free as they had wished. After having lost the studio grounds to Mitchell, they had to find a new strategy. That was already clear in 1924. They silenced the 2709 as well as possible but almost fruitless. Mitchell had a new movement from 1928 on, noiseless, plus the simpler rackover system. Why I am telling all this?
Because it was decided to exploit the tremendous advantage not directly with everybody but indirectly via licence holders. That way they could shift the risk onto others, institute regular income, and control the technical development. In September 1929 they opened a large research-development lab on North Rockwell street and explicitly invited for the solution to cinematographic problems. The years from 1929 to 1939 were quite tough for B. & H. due to an ever increasing competition on 16mm projectors, a new perforation standard introduced by EKC (KS), the complete flop of the Filmo Straight Eight, many things demanded from the Eyemo (larger base after an unaccepted sole, more flexible finder, longer run, sound aperture, centering of lens ports on new aperture, rackover, critical focus, better motor interface), and saturation of the perforators market. In fact, EKC had its perforator shop so enlarged to have become independent. Du Pont tried their own perforator designs. Agfa relied on suppliers in Germany. France had its own industry. The Soviets would buy Bell & Howell perforators from the early 1930s on. A Bell & Howell 35mm perforator would cost US$ 16,600 today. Ferrania bought BH perforators in 1934. Gevaert was Debrie equipped. It’s complicated.
Does anyone know of another lens similar to the Kern Switar 5.5mm and wider than the 6.5 Rodenstock that will work with my camera?
I don't think you'll find any other lens that works, it's a unique mounting thread/flange depth combination, using the D mount thread but with a deeper distance from lens seat to film plane. Normal D mount lenses would need to be seated several mm inside the camera mount to focus properly, which just isn't possible. You'll have to live with 6.5mm as your wide angle, or use a different camera, like a Beaulieu MR8 if you want reflex viewing with D mount lenses.
If you were very determined I suppose you could find a wider angle C mount lens (which would have a longer back focus distance) and have a custom adapter made, but it would be expensive and require exact knowledge of the Nizo FFD, and C mounts wider than 6.5mm aren't common, and it might have a thicker barrel and foul on the lens above anyway. Doesn't seem remotely worth the effort.