Biography

Discussion

Even as a young man, Frits Prinsen was greatly interested in technology. Encouraged by his mother, he familiarised himself with new technical phenomena, such as radio transmitters and receivers, automobiles, and the first gramophone. He was fascinated by historic figures such as Edison, Zeppelin, and the Wright Brothers, who inspired him to undertake technical experiments at an early age. At technical school, Prinsen acquired skills in electrical engineering, becoming a full-fledged engineer through self-study. Experimenting with technical equipment was Prinsen’s love and his life. Due to his enthusiasm, amiability, and naivety, he sometimes revealed more about his latest inventions than he should have. Consequently, others repeatedly profited from his ideas.

Prinsen’s chief inventions were made in the areas of photography, cinematography, and movie projection equipment. To break the routine, as it were, he also developed a ‘dexterity roulette’, stereo projection systems that had no need of special eyewear, and a three-dimensional colour television. He also built a gyroplane, which he exhibited at the Aviodrome.

Prinsen was in regular contact with Philips in Eindhoven, working on an improved movie theatre projection lamp. He accepted Philips’ invitation to work as an engineer in the ‘big lamps’ department. Interested in the development of high-quality sound film, Philips commissioned Prinsen to develop sound film equipment in collaboration with Loet Barnstijn, a Dutch film magnate. One problem at this time was synchronising the spoken word with lip movements: more often than not, the actors’ lips failed to match the sound. Talking movies were furnished with sound via gramophone plates: in professional circles, referred to as ‘needle sound’ (‘naaldgeluid’). Prinsen and Barnstijn’s efforts resulted in the ‘Loetafoon’ (‘Loetophone’), a projection device with ‘needle sound’, universally praised for its improved lip synchronisation. Prinsen continued to ponder and work on developing a better system. In the end, he managed to make a major contribution to the development of optic sound, also called ‘light-sound’ (‘lichtgeluid’). This is a process in which the soundtrack is located on the film strip itself and based on the modulation in the rhythm of the sound vibration: the optic soundtrack is read by a photocell and electronically amplified.

Prinsen’s most important invention was the development of an automatic diaphragm for photo and film cameras in 1931. To achieve this, he used a photocell that he had modified himself. Thanks to this automatic device, the user no longer had to worry about setting the proper exposure for hi photographic material. The patent transcript for Prinsen’s invention clearly confirms that the automatic diaphragm already existed in a non-transportable form, accompanied by an amplifier and powered with or without batteries. The power source was necessary for the diaphragm to work. The existing system, however, was too large for an amateur camera. What was innovative about Prinsen’s design was the use of a photocell that supplied sufficient power to adjust the diaphragm without an external energy source or amplifier. By using extremely lightweight materials, several microamperes of power was all that was required. The light weight of the device proved to be somewhat vulnerable, but this glitch could be solved by spring-mounting the construction.

Prinsen invested substantial capital in the development costs and both the domestic and foreign patents. Moving from the usual optical and chemical light meters to automatic lighting technology, however, proved to be too big of a step, both for the camera industry and the consumer. In his mobile laboratory (one of the first caravans), Prinsen built a semi-automatic camera, which, though patented in Germany and Austria, was never put into production. The public seemed to be more than satisfied with the development of the standard electric light meters, as affirmed by the modest sales figures for the Super Kodak Six-20 Camera, a camera with automatic exposure brought out in 1938. Over a period of six years, no more than 725 units were sold. It was a development signalling a milestone in photography, but one not yet ready to become a commercial success. Businesswise, Prinsen enjoyed more success with his light meters in the highly competitive market prior to World War II than with his automatic diaphragm. He also continued manufacturing light meters in the years after the war: the successful ‘Prinsen Colour’, with the diaphragm f-numbers indicated on the pointer, ensuring the values were directly readable; the more simply constructed Prinsen-Simson; and the Prinsen-Directa, developed for the French market (also sold in the Netherlands starting in 1950). With an eye to the budding colour photography industry, Prinsen also responded to the allure of being able to adjust the colour temperature of light. For this purpose, he developed the Kelvina and Keiven tri-colour temperature meters. In addition, he started up the production of an automatic ancillary diaphragm that could be mounted to the front of existing photo and film cameras.

After World War II, practically nothing was available in the Netherlands in the area of photographic equipment. There was a shortage of natural resources and the importation thereof was difficult due to the lack of foreign currency. The German photo industry had come to a complete standstill. For a brief period of time, opportunities to establish new photographic manufacturing companies or to expand on those already existing arose in the Netherlands. Several companies, including ‘De Oude Delft’ in Delft and ‘Cambo’ in Hengelo, took advantage of this opportunity. A small number of businesses were involved for several years­—initially with relative success—in the production of basic photographic equipment for amateur use. Besides Vena in Amsterdam, Tahbes in The Hague, and Nefotaf in Weert, Prinsen also came out with a simple camera for the Dutch market.

In 1947, Prinsen devised various apparatus, including a box camera with a built-in flash device. By abandoning the use of a built-in viewfinder, Prinsen saw an opportunity to create space for a battery holder and a lamp fitting. The extremely flat lamp reflector was affixed to the lamp fitting when used, and once it had served its purpose, it could be stowed away at the side of the camera.

Together with the chief editor of Focus, Hille Kleinstra, Prinsen worked on a system for automatic focusing, leading up to what became the first autofocus camera. He initially experimented with a mechanical system for this purpose, based on gravity. He later adapted two photocells for an electronic autofocus system. This led to a working model based on an Agfa Flexilette 35mm camera. Through the implementation of infrared radiation and sonar, Prinsen’s systems were soon out-dated. In this area, his efforts ultimately failed to achieved any concrete results.

In 1955, Prinsen ceased with all of his entrepreneurial and manufacturing activities, likewise shutting down his company in Delft. He continued his endeavours as an inventor with undiminished fervour, however, and in 1959, he started working for Agfa in Munich, Germany. More than a quarter of a century after his initial invention, it was now his task to perfect the automatic diaphragm. A number of Agfa’s models, both for film and photo cameras, were equipped with Prinsen’s fully automatic diaphragm.

The automatic diaphragm was Frits Prinsen’s most important invention. Considering the millions of cameras equipped with an automatic diaphragm that have since been built in Germany, the United States, and Japan, the significance of his invention has been proven beyond a doubt. For both the professional and the amateur, setting the correct light exposure for light-sensitive materials had been a problem for years. The arrival of electronic light meters in the 1930s brought some improvement, but using the equipment still required considerable attention. The automation of photographic equipment has contributed greatly to the popularisation of photography. For journalistic and reportage photographers for whom urgency is essential their work, this type of camera was a welcome solution. The Dutch inventor Frits Prinsen was one of the most important pioneers in this revolutionary development of the photo camera.

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