Snatching failure from the jaws of success
The Universal Camera Corporation released the first Mercury Camera in 1938 and it proved to be a great success in the market. The innovative precision design included a high-speed rotary focal plane shutter that was equal in accuracy and reliability to the Leica or the Contax at a tenth the price.
The first model of the Mercury used 35mm film in a proprietary cassette and produced half-frame negatives. The lenses available for the camera were orginally produced by Wollensak and provided adequate resolution to support the small format.
A post-war redesign produced the Mercury II Model CX with a slightly larger case which enabled the use of standard 35mm cartridges. Lens production was moved in-house, and the 35mm Tricor f2.7 was given an anti-reflective coating while retaining the sharpness of the earlier lenses. A modification of the shutter had been undertaken earlier to increase the maximum speed from 1/1000 to 1/1500 -- the fastest then available -- but it was abandoned due to reliability issues.
In addition to sporting the unusual shutter, the Mercury made the half-frame format very popular for a time just after WWII. The format was reintroduced in the 1960s by Olympus and others, and took over the industry for about five years until it was found that additional miniaturization could support a full 35mm frame. The camera's designer, George Kende, also introduced the hot shoe for synchronizing flash which also became a standard for the industry. In spite of all the good things the Mercury had going for it, the company went bankrupt in only a few years after the war. The fault likely lay not with engineering, but rather with a surrender to marketing hype coupled to bad management and financial decisions.
In sorting out the fate of the Mercury camera it is instructive to compare the actual camera to an introductory passage in the camera's manual:
...To assure the sharpness of negatives necessary for good color photography, the old-fashioned ideas of negative size had to be discarded. Universal engineers incorporated in the Mercury, the same size 35 mm. negative as is used for the projection of motion pictures shown in your local theatre...
That is mostly nonsense. The hype-artists were trying to invoke the idea of images produced on the big screen and conflating that with the use of the half-frame format in a miniature still camera with the implication that image quality would be superior to full-frame.
What was really going on in regard to design were some perfectly reasonable compromises coupled to real-world experience. The designer, George Kende, did in fact have a useful background in rotary shutter development implemented in motion picture cameras. Making the idea work in a small still camera using 35mm film, however, dictated the use of the half-frame format. Looking in at the open back of the camera it is obvious that trying to use the rotary shutter with a full 35mm frame would have resulted in a camera that was about half again as large and perhaps twice as heavy as the Mercury. It just would not have gotten off the ground given the competition.
Had design considerations been given some priority over the decisions of ad flacks and bean counters it seems possible the Mercury might easily have retained a big share of the small camera market. There was certainly some room for improvement. For instance, devoting all that surface space to a depth-of-field chart divided between front and back, and that unbelievably complicated exposure-calculating dial had some 'Forties geek appeal, but gave very little real help to making well-composed and exposed images.
The other big lack in the Mercury was a built-in coupled rangefinder, or better yet a reflex finder. Or, they could even have used both of those viewing systems together as was done with the little 35mm Bolsey Reflex. There was certainly plenty of space in front of the top shutter hump to play with those possibilities, and any would have helped resolve the close-up parallax issue which plagues the Mercury shooting experience.
Another possibility would have been to go the route of the Robot camera and use a square image on 35mm film which would have gained some surface area while eliminating the need to rotate the camera for compositional purposes.
Speculation aside, the Mercury II as it stands is a good shooter with interesting features and history. At a time when film prices are going up quickly, there is also some appeal in the idea of getting twice the normal number of images from a roll of film.