Before emigrating, Ruth Jacobi worked at her family's photo studio in Berlin, which had been running for four generations. Between 1920 and 1922 she received a professional education in photography at the Photografische Lehranstalt des Lette Vereins, a progressive Berlin establishment given to the advancement of women, and the only place, apart from the Bayerische Lehranstalt für Lichtbildwesen in Munich, where women could study photography. Lessons included portrait photography and technical photography, as well as how to take portraits at different times of day, landscape and architectural photography, colour photography, reproductions and ink or overpainting.

In 2004, 400 of Ruth Jacobi's photographs were donated to the Jüdisches Museum in Berlin. The estate was in the possession of a sister-in-law of Ruth Jacobi in Massachusetts (exh. cat. Ruth Jacobi, 2008). In spite of this donation, her photographs are still rarely found in either public or private collections. Unlike her sister Lotte Jacobi, who has been the subject of research, Ruth Jacobi continues to be understudied, although her images were published in a number of magazines during her time.
One source of information is her memoir "Thorn", which contains fragmentary and disorganised descriptions of her life. It can be assumed that the memoir was written in the 1970s. She submitted a version of the memoir, with accounts of her life ending in 1922, to the Leo Baeck Institute in 1987. Another version, in which her accounts extend to 1939 is archived at the Akademie der Künste in Berlin.

Ruth Jacobi saw herself as a progressive and avantgarde photographer. In "Thorn", she describes the conflicts in her parents' studio between the old, traditional methods of portrait photography and the newer approach of the 1920s. “Ende des Jahres 1922 fing ich an ernsthaft im Atelier meines Vaters zu arbeiten. […] Jede Aufnahme die machte wurde ein Ereignis fuer mich. Es schien mir – als wuerde ich jetzt erst anfangen zu sehen. Ich sah Alles in einem neuen Licht. […] Mia [R.J’s mother, HR] erkannte das Neue in meiner Photographie: die junge – die neue Generation. Vater – Meister Jacobi war kritisch. Ihm gefielen meine Portraits gar nicht: 'die grossen Koepfe – wo jeder Zug in de Gesichtern entbloesst war'. Dazu kam noch – dass ich gegen – Retuschieren war. Tortzdem ueberliess er mir das Photographieren mehr und mehr.” (Jacobi 1970 ) She also writes about how she got involved with the Berlin intelligentsia, whose members came to the studio to commission portraits, how she put on her first small exhibitions in the shop window of her studio and succeeded in publishing her images in magazines.

The end of the 1920s marked a new stage in her life. Together with her husband Hans Richter, whom she married in 1926, she decided to emigrate to New York in 1928. In the metropolis she searched in vain for employment as a photographer, but was able to find only freelance jobs. Shortly after her arrival in New York, she made a series of pictures of poor Jewish street vendors and life on the Lower East Side. Her sensitive, humanistic images, taken with a Leica, capture unguarded moments amidst the hustle and bustle of the streets and made Ruth Jacobi an important figure in social photography. During her lifetime only few images of this series were published. In 1931, they were used for the cover and the book design, designed by John Heartfield, of the German edition of Michael Gold's autobiography, Juden ohne Geld (Jews without Money), in which he describes his childhood on the Lower East Side in New York City, at the time a poor area populated by emigrated East European Jews.

In addition to this social approach to New York, Ruth Jacobi, like many of her émigré colleagues, also focused on the city's skyscrapers, using tightly cropped and upward tilted perspectives. Her aim was to experience the metropolitan architecture through her camera. In 1932, four images of her street scenes, signed with “Jacobi, Berlin”, were published in New York, a photobook and essay collection by the Austrian émigré Ann Tizian Leitich. This publication of her images puts her on an equal footing with the book's internationally renowned photographic contributors. Among them were Edwing Galloway and Emil Otto Hoppé. Agencies that contributed included Presse-Photo, Berlin and Mauritus (a photo agency which was found by Ernest Mayer, who later was co-founder of Black Star Agency in New York). The book's images chimed well with the huge interest in New York that existed in 1930s Europe.

As her marriage with Hans Richter did not go well, Ruth Jacobi returned at the end of the 1930s to Berlin, where she went back to work at the family photo studio alongside her sister Lotte Jacobi. But only two years later, with the boycott of Jewish businesses imposed on 1 April, 1933, the situation rapidly deteriorated and the family made efforts to publish under pseudonyms like "folkwang-archiv", "Behm's Bilderdients" and "Bender-Jacobi”. In 1933, Lotte Jacobi resumed a previous relationship with her first love, Zsolt Roth, and their marriage in Budapest and a joint trip to Hungary followed.

As the situation in Europe under the National Socialists continued to get worse, Ruth and Zsolt Jacobi-Roth emigrated in 1935 via Le Havre to New York. A few months later in 1935, her sister Lotte Jacobi arrived in New York and in 1936 her mother Mia Jacobi (1872–1950) and the son of Lotte Jacobi, Joachim Jacobi (1917–1985; who Americanised his name into John Hunter) followed. That same year the two sisters opened a studio together on 1393 Six Avenue 57th Street, which they ran until 1936, when they each opened studios of their own. Ruth Jacobi’s studio was located on the corner of Madison Avenue and East 58th Street, only one street west of the old studio and close to a number of other galleries such as the Julien Levy Gallery and the Matisse Gallery, where she also held classes as well as to Lotte Jacobi's studio. Towards the end of the 1930s, since the studio was not profitable and the rent was high, she gave up her studio to support her husband in his medical practice. It was located on the first floor of their house in Astoria (Queens), where they lived on the second floor. Images of Astoria, taken by her émigré colleague Rudy Burckhardt, show that Astoria was not as densely populated as Manhattan during the time, but enjoyed rich cultural diversity, including German emigrants and Jews.

Only very few images have survived from Ruth Jacobi's "second" time in New York, but the considerable number of photographs that appeared in magazines as Popular Photography and U.S. Camera show that she achieved success and built something of a reputation in the 1930s and 1940s. A photograph of dolls was published in the December 1937 issue of Popular Photography and was followed by an image of twin sisters in February 1938. The latter was described thus: “The charming photograph of the twin sisters by Ruth Jacobi-Roth is a candid shot taken without their knowledge and consequently not posed.” (Anonymous 1938, 68) In March 1938, her picture of grapes was highly praised and selected as “Picture of the Month”: “The study of the grapes by Ruth Jacobi-Roth possesses a naturalness and quality that can be obtained only by one who has mastered photographic technique and lightning. This ordinary subject, in the hands of an artist, has been made into a still-life of luscious beauty.” (Anonymous 1938, 42) In the same issue was printed another image of rag dolls, sharing a double-page spread with the émigré photographer Walter Sanders and Philippe Halsmann. In the March issue of 1939, for the "Salon Section 1-2-3”, a montage of three pelicans was published, featuring a single image of a pelican taken by Jacobi at the Berlin Zoo using a 9x12 reflex type camera. Popular Photography was an important magazine for émigré photographers, who were able to publish both their images from their previous times in Europe as well as newer photographs from their exile in New York. Among the émigré photographers published were Lucien Aigner, Ruth Bernhard, Erwin Blumenfeld, Josef Breitenbach, Alexey Brodovitch, Rudy Burckhardt, Alfred Eisenstaedt, Andreas Feininger, Philippe Halsman, Fritz Henle, Lilly Joss, Clemens Kalischer, George Karger, André Kértész, Hermann Landshoff, Lisa Larsen, Herbert Matter, Hansel Mieth, Lisette Model, Martin Munkacsi, Fritz Neugass, Walter Sanders, Kurt Safranski, Xanti Schawinsky, Rolf Tietgens, Werner Wolff, Roman Vishniac and Ylla.

In 1940, a portrait study of a sleeping girl by Ruth Jacobi was published in U.S. Camera. It appeared in the edition to mark the 100th anniversary of the magazine and was selected by the photographer and editor Edward Steichen (who became in 1947 curator of the photographic department at the Museum of Modern Art). At this time, when she was already working less as a professional photographer, she was presented on equal footing with her sister Lotte Jacobi.
During the 1940s Ruth Jacobi also produced experimental photographs and photograms and took painting lessons with Zoltan Hecht und Hans Hofmann. In the 1970s she returned to photography, doing experimental work and nature studies and also taught at the Jewish Institution of the Educational Alliance.

Ruth Jacobi’s photographic estate from her time in Germany is almost completely lost. The photographs that have survived consist of portraits, still lifes, nature and plant photographs, and travel photography. Often these are undated and without names, which makes it difficult to assign them and does not reveal exactly which photographs were taken in exile in New York. The series of photographs taken in 1928 in New York are fortunately assignable and consist of a series taken on the Lower East Side and city views. The photographs of the skyscrapers, window washers or park entertainments show very clearly Ruth Jacobi’s experimentation with the camera in the urban space and reflects the photographic modernistic style of the 1920s. These aesthetics can also be recognised in her portraits, which are often in close-up, in profile and cropped, also demonstrating the principles of the “New Woman”. Through her work at the portrait studio she mastered the art of lighting which she applied to her still lifes such as the grapes. Two of her cameras, a Leica and a Rolleiflex, are stored in the Jüdisches Museum in Berlin.