PhotoLexicon, Volume 5, nr. 9 (September 1988) (en)

Frits Prinsen

Luc Verkoren


Frits Prinsen devoted his professional life to working on inventions. A significant number of his creations—of which there are hundreds—are related to photography and cinematography. The automatic diaphragm, which put an end to the problem of setting the correct exposure time, is undoubtedly his most important invention. Prinsen is also credited with devising light meters, colour temperature meters, and a box camera with a built-in flash.




Frederik Berthus Archibald (Frits) Prinsen is born on 28 September in Den Helder. His father is the city’s municipal secretary.

During the evenings, Frits trains to become an electrotechnical engineer through self-study.


On 22 November, Prinsen produces the first Dutch high-vacuum electron tube for use in military radiotelephony, while working for his first employer the ‘NV Metaaldraadlampen Fabriek “Holland”‘ (‘Metal Wire Lamps Factory’) in Utrecht.


Philips hires Prinsen as an engineer in the ‘large lamps department’, where projection lamps and other apparatus are manufactured. In November, Prinsen’s design for a suspended movie theatre projection lamp with an internal mirror is demonstrated in Eindhoven, simultaneously with a new wide-aperture projection objective and a powerful sound installation developed by Philips.

Hereafter, Prinsen becomes involved in the production of projection equipment for motion picture film. This leads to the building of the so-called ‘Loetafoon’ (‘Loetophone’), a projector that produces lip-synchronised sound with the assistance of gramophone albums.


Prinsen’s first ‘lichtgeluid apparaat’ (‘light-sound device’) is completed on 9 June: a projector for motion picture film featuring an optic soundtrack. The first movie house equipped with this device is the Passage Theatre in The Hague.


Prinsen is involved with the recording and pressing of the first gramophone record in the Netherlands: a recorded speech given on 9 August by Evert van Dijk, a commercial pilot.

On 12 December, Prinsen conducts his first tests with an automatic diaphragm.


On 30 December, Prinsen completes his design for an automatic diaphragm to be used with 8 mm film devices, which has a lens aperture ranging from f4.5 to f16.


Prinsen makes a photoelectrical light meter. The first model is completed on 30 June. On 4 October, he files a patent request for a lux meter, a light meter, and an automatic diaphragm. He patents this last invention both in the Netherlands and abroad. The director of the oldest camera manufacturing company, Voigtlander, located in Braunschweig, Germany, is interested, though he still believes a fully automatic diaphragm is too risky.


Prinsen installs an automatic diaphragm in a 16 mm film camera manufactured by the Dutch-Swiss brand Schalie-Colleé. He takes his first film shots with this automatic prototype on 3 April.


Prinsen manages to attract the interest of the managing board of Ditmar, a heating unit manufacturer in Vienna, in the production of 5,000 film cameras with automatic exposure. With the advent of the German ‘Anschluss’, however, these plans never come to fruition.


On 15 November 1938, Prinsen establishes the ‘Laboratorium Prinsen’ (‘Prinsen Laboratory’) in Rotterdam.

On 1 September 1939, the laboratory relocates to the town of Beek, near Nijmegen. The company manufactures light meters in serial production.


The laboratory in Beek and an affiliate established during World War II in Kranenburg, Germany, are badly damaged during war combat.

Prinsen devises a fully automatic ancillary diaphragm for both photo and film cameras.


Prinsen moves to Delft. On 22 December, he demonstrates a box camera with a built-in flash installation. Shortly after, he is commissioned to build ten thousand flash box cameras on behalf of camera wholesale companies, to be delivered within six months.


On 20 January, Prinsen and A.W.H. (Bob) Kommer try out a prototype for a portable electron flash with a shutter speed of 1/20,000th of a second at Kommer’s studio in The Hague. The shots that Kommer takes using this electron flash device are also obtainable with traditional flashbulbs, but the latter utilises only a fraction of the total light produced.


On 22 August, the ‘Laboratorium Prinsen’ in Delft is shut down. The company’s official closing date is set retroactively to 1 January.


Prinsen is hired by Agfa in Munich, Germany. His task is to further develop his automatic diaphragm.


Together with Hille Kleinstra, Prinsen builds an automatic distance setting on an Ilford 35 mm camera. He also experiments with distance settings achieved with the help of two photocells on an Agfa Flexilette camera.


On 19 September, Prinsen demonstrates his ‘Prinsen Panorama 3-D Television’ at Bob Kommer’s film studio in The Hague.


Frits Prinsen dies on 15 November in The Hague.


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.


Primary bibliography

Urheberrecht auch auf Wissenschaftliche Werken und Erfindungen, Den Haag (Ver. voor auteursrecht op wetenschappelijke werken) z.j.

Holografie, in tff. Maandblad voor foto- en filmtechniek (april 1968) 4, p. 7-9.

Maser en laser. Holografie, in tff. Maandblad voor foto- en filmtechniek (mei 1968) 5, p. 7, 9.

Holografie, in tff. Maandblad voor foto- en filmtechniek (juni/juli 1968) 6, p. 17-19.

Parallax stereogram, in tff. Maandblad voor foto- en filmtechniek (oktober 1969) 9, p. 15, 17-18.

Parallax-panoramagram, in tff. Maandblad voor foto- en filmtechniek (februari 1970) 2, p. 5-7.

Parallax-panoramagram in Nederland, in tff. Maandblad voor foto- en filmtechniek (juni 1970) 6 . p. 14-18.

3 D gisteren en vandaag, in tff. Maandblad voor foto- en filmtechniek (juli/augustus 1970) 7/8, p. 13-14.

Video recorder deel 1, in tff. Maandblad voor foto- en filmtechniek (oktober 1970) 10, p. 6-8.

Video recorder deel 2, in tff. Maandblad voor foto- en filmtechniek (november 1970) 11, p. 12-14.

Integraal fotografie, in tff. Maandblad voor audio-visuele technieken (januari 1971) 1, p. 9-10.

De ‘metro-cinemobil’, in tff. Maandblad voor audio-visuele technieken (maart 1971) 3, p. 12-13.

Auto-focus-systeem voor dia-projectoren, in tff. Maandblad voor audio-visuele technieken (april 1971) 4, p.6-8.

Auto focus systeem voor camera’s met slinger of pendel, in tff. Maandblad voor audio-visuele technieken (mei 1971) 5, p. 18-19.

Auto focus met contrast principe, in tff. Maandblad voor audio-visuele technieken (juni/juli 1971) 6/7, p.6-8.

Auto-focus voor kleinbeeld camera’s, in tff. Maandblad voor audio-visuele technieken (maart 1972) 3, p. 14-15.

Autofocus voor kleinbeeld camera’s, in tff. Maandblad voor audio-visuele technieken (april 4, p. 16-17.

Secondary bibliography

(Verslag over 30e Koninklijke Nederlandsche Jaarbeurs), in Het Vaderland. Avondblad D, 14 maart 1934.

KL, F.B.A. Prinsen ing., in Foto 21 (juni 1966) 6, p. 244-245.

tff. Maandblad voor foto- en filmtechniek (april 1968) 4, p. 7.

Piet van der Ham, Nieuwe aanpak van de driedimensionale fotografie, in tff. Maandblad voor audio-visuele technieken (maart 1973) 3, p. 3-5.

H.J. Oolbekkink, Ing. Frederik Berthus Archibald Prinsen, uitvinder, in Leidsch Dagblad 27 september 1975, p. 25.

Auteurs onbekend, Wat een uitvindingen. Ing. F.B.A. Prinsen, Dordrecht (Sari B.V.) z.j. (ca. 1977).

PJ. van der Zanden en Luc Verkoren, Een kans gemist?, in Photohistorisch Tijdschrift 5 (1982) 4, omslag, p. 7-9.

Luc Verkoren, Prinsen en de automatische belichting, in Foto 37 (april 1982) 4, p. 71-72.

Luc Verkoren, Drie boxcamera’s. Prinsen, Philips en Foka, in Photohistorisch Tijdschrift g (1986)3, p. 4-8.


1934, 15 oktober, Nederlands octrooi nr.33922 (automatisch diafragma voor gewone en kinematografische camera’s, werkende door middel van een lichtgevoelige cel).

1935, 15 augustus, Nederlands octrooi nr. 36097 (fotometer voorzien van een foto-voltaïsche cel, ook wel aangeduid als foto-elektrische belichtingsmeter).

1952, 15 juli, Nederlands octrooi nr. 70387 (boxcamera met ingebouwde synchroonschakeling voor flitslampen).

(Een uitvoerige lijst van geoctrooieerde vindingen van Prinsen is opgenomen in het boekje Wat een uitvindingen, p. 181 e.v.).


Delft, Kamer van Koophandel (dossier 7348).

Delft, Technisch Tentoonstellings Centrum (TTC), archief.

Leiden, Prentenkabinet, bibliotheek en documentatiebestand.

Nijmegen, Kamer van Koophandel voor Nijmegen en omstreken, (dossier 6886).

(De gegevens van de Kamer van Koophandel te Rotterdam, dossier 54205, zijn vermoedelijk in de oorlog door brand verloren gegaan).


Amsterdam, Filmmuseum.

Delft, Technisch Tentoonstellings Centrum (TTC).

Den Haag, Museon.

Leiden, Prentenkabinet van de Rijksuniversiteit.