Jonas Ferdinand Gabriel Lippmann, a Luxembourgish-French physicist, is known for the innovation he brought to the color reproduction method in photography and for having produced the first color photographic plate. His method was based on the phenomenon of interference. His discovery enabled the total reconstitution of all wavelengths reflected by an object. Using an emulsion on a mercury surface, which reflects the incident light, both the received light and the reflected light produce standing waves that reproduce the original colors of the photographed object. This method is not practical because long exposure is necessary and no copies can be made. It also has no connection with modern methods. For this work, he was the Nobel laureate in physics in 1908. He was also known for his discovery of heliochromes, microscopic analyses, and of the Lippmann electrometer. In recognition of his work for developing the method of photographically reproducing colors based on the theory of wave interference, Lippmann was appointed Professor of Mathematical Physics at the Sorbonne. Lippmann enriched the field of scientific research with significant contributions to the fields of optics, thermodynamics, photochemistry, electricity, and astronomy.

The inventor of color photography was a member of the French Academy of Sciences in 1886 and was elected as its president in 1912.

1 The life of Lippmann or lux aeterna

Lippmann was born on 16 August 1845 in Hollerich, in Hollerich, in the Grand Duchy of Luxembourg. His mother, who was from Alsace, took care of his education, and his father was a tanner in the region of Lorraine. Later, the entire family moved to Paris, where Gabriel received his early education. In 1858, Lippmann followed the “Lycée Napoléon” (today known as Henri-IV). While at the “Lycée”, he was acknowledged for his attention to history, Latin and other languages such as English and German. During this time at the “Lycée”, he was also interested in philosophy because of his teacher Nourisson. However, his physics teacher, Mr. d'Almeida, gave him a taste of the physical sciences. In 1870, d'Almeida and his friend Marcelin Berthelot had put such science in the service of the motherland. Almeida first proposed using microscopic photographs as a means of correspondence, which allowed the province to correspond with the capital using carrier pigeons. Under the influence of Almeida, Lippmann headed the scientific section of the “École normale” (normal school), which he entered in 1868 at the age of 23. He was only a few years older than his colleagues. He was first admitted to eligibility with good grades in mathematics and physics and a mark of 20 in composition in foreign languages. During these years at the “École normale”, Lippmann became much more interested in his personal scientific research than in his courses. The Deputy Director and Lecturer of Physics, Bertin, was interested by his inquisitive mind as a researcher. Lippmann was particularly interested in the oscillatory discharge of a capacitor. He realized that during this discharge, the current was not uniformly distributed in a straight section of the driver because of the increasing self-induction. This phenomenon is often referred to as the skin effect and plays a large role in the theory of electrical waves and wireless telegraphy. Such topics were not included in the aggregation programs and were thus slightly neglected by Lippmann. Lippmann was also more interested in scientific work, but he did not pass the final examination as a teacher at the “École normale”. He had no degree of worship. How could one who did not want knowledge for its own sake and was independent of mind-relevant information clear a new area of knowledge?

Between 1872 and 1875, Lippmann was charged by the French Government with several missions to visit Germany to study methods for teaching science, and he chose to work with Kühne and Kirchhoff in Heidelberg, and with Helmholtz in Berlin. These distinguished German researchers had always shown him the greatest kindness and became interested in his work. In 1875, Lippmann returned to Paris; at first, he worked at home with a few instruments on loan from the “École normale”, but he subsequently worked at the Sorbonne University. He completed his thesis on electrocapillarity and defended it on 24 July 1875, achieving “summa cum laude” distinction. His thesis was entitled Relations entre les phénomènes électriques et capillaires, and Kirchoff served as the doctoral advisor. It must be mentioned that Herman von Helmholtz was also an academic advisor. After this beginning, as a “maître de conferences” (MdC), he was attached to the lab JAMIN until the end of 1878, when “maître de conferences” positions were created in the science faculties. Then, he had a stable position and some means to work. Lippmann remained as MdC until 1883. At that time, the mathematical physics chair became vacant following the death of Briot. Lippmann was then named a professor at the Sorbonne University and head of the laboratory of physics.

Lippmann taught at the Faculty of Science for over 40 years and many French and foreign scholars and students worked in the laboratory of Lippmann, where they produced original studies. One of his more interesting collaborations was with the young Polish student Marie Skłodowska (Curie), as well as with Maurice Couette and Pierre Curie.

Education was a major concern for Lippmann. He repeatedly set out his ideas on this concern in lectures and speeches.

2 Research activities or a success story of the color photography

As a passionate man of science, Lippmann chose to develop his own path in the “jungle” of knowledge and succeeded…

The scientific activity of Lippmann is distinguished by his contribution to several discoveries in physics such as piezoelectricity, time measurements, the coleostat, integral photography and color photography. Both during his time at the school and after leaving the school, Lippmann thought that there might be a relationship between electricity and capillarity. His intensive research led him to develop the capillary electrometer, or “Lippmann electrometer”. Lippmann also stated a theory of pyroelectricity, where crystals such as tourmaline that were subjected to heating or cooling exhibited electrical events at specific locations on their surface. In 1879, in a note entitled “Action magnetism moving about static electricity; inertia of static electricity”, he deduced that a moving magnet exerted a remote mechanical action on an electrified motionless body, and he concluded that static electricity had its own electrical inertia. The permanent color spectrum was obtained based on Zenker's explanation on reflection holography and Maxwell's electromagnetic theory. The Lippmann process, which yields colors, is a method for producing colored photographs of objects without using dyes, which is in contrast to the three-color processes. This method uses a layer of mercury in a special holder behind the photographic emulsion of an orthochromatic or panchromatic glass plate. The emulsion side of the glass plate faces away from the lens and is in optical contact with the mercury mirror. Light rays that reflect off the mercury layer interfere with the incident light rays and form regular standing waves and latent images at different depths according to the colors. After the development, the film contains a series of layers of silver deposits where the light acted and intermediate places where silver was not reduced. The reflected lights from two layers add together to produce more light only if the two waves are in phase, which occurs when the distance between the layers is half of the wavelength of the light. The film appears with an identical color when it is viewed afterwards from the emulsion side due to the ordinary reflection, whereas the image appears negative due to the transmitted light (because the space between layers is determined by the light that falls on the film). The Lippmann method is a symmetrical two-step process of interference-mediated encoding and diffraction-mediated reconstruction to generate color photographs on a black-and-white medium.

Lippmann was an active member of the Academy of Sciences and its president. Moreover, he was a foreign member of the Romanian Academy, Royal Society of London, and Grand Ducal Institute of Luxembourg. He was a member of the “Société francaise de photographie” (1892) and its president (1896–1899). Lippmann was one of the founders of the “Institut d'optique théorique et appliquée” in France. In Luxembourg, in his tribute and recognition, the Centre for Public Research – University Center, which was created in July 1987 in Luxembourg City, changed its name on 31 May 1999 to that of Public Research Centre Gabriel Lippmann (1999–2014). However, the Public Research Centre – Gabriel Lippmann later merged with the Public Research Centre – Henri Tudor on 1 January 2015, and formed the Luxembourg Institute of Science and Technology (LIST).

Lippmann was a distinguished man with reserved manners, tender conscience and infinite scruples. His mother was a woman of rare distinction of mind and had a great influence on him. With her remarkable musical gifts, she developed in Lippmann a taste for classical music from childhood. From his father, a tanner, he obtained a sensitive colorist's eye to notice the effects of color degradation. This is the artist physicist! He took extreme pleasure in contemplating the effects of light in landscapes.

Lippmann was passionate about literature: he could recite full acts of plays from the classic French literature and from Shakespeare's ones. He could give a lecture on any novel by Walter Scott. The high culture of Lippmann was further refined in the circles that he frequented after his marriage (1888) to the daughter of Victor Cherbuliez (novelist and author). Miss Cherbuliez was a valuable collaborator and research associate to her husband in the study of colors in photographs; they realized together admirable photographs.

“Life is short and progress is slow,” said Gabriel Lippmann in 1908.

He died on 13 July 1921 while returning from a voyage to Canada. His research continued to live. The intelligence of Lippmann, which was an intelligent integral to fundamental physics, was a revolutionary strategy for progress in engineering and our society. Later, Denis Gabor became a Nobel laureate in Physics (1971) for developing the holographic method, which extended photography in the three-dimensional space. The works of Lippmann and Gabor enabled the evolution of two- and three-dimensional hologram studies by Yuri N. Denisyuk in 1962. A new technique to record Lippmann color holograms was described by Kubota: using three recording wavelengths that correspond to the three primary colors, using a holographic stereogram.

Lippmann, sanctus sanctorum, devoid of all ambition, lived only for research, and the idea of drawing some profit from his discoveries never occurred to him. Absorbed in his dream of a scholar, we must admire the disinterestedness of this scientist.