Along with Josef Breitenbach, Fred Stein and Ylla, Hermann Landshoff was one of the photographers who arrived in New York in 1941. He was born in 1905 in Munich-Solln, the son of a Jewish family of musicians. The family home was a meeting place for such renowned intellectuals as Thomas Mann, Rainer Maria Rilke, Albert Einstein and Christian Morgenstern. The close-knit family could boast talent in music, literature and science, and Landshoff's younger sister Ruth pursued a career as a sculptress in New York. The sister of Hermann's father, Hedwig Fischer, was married to the publisher Samuel Fischer and Hermann's cousin, Ruth Landshoff-Yorck, was a successful actress in Berlin in the 1920s. She emigrated to New York in 1939 and became a writer. After attempting to become a caricaturist and draughtsman, Hermann Landshoff decided to teach himself photography. In his autobiography, he says of himself: "I hated high school. After school I learned to draw, especially caricatures, characters and typography at the School of Arts and Crafts and with my teacher, whose assistant I was. I took my first photo when I was 24 years old. Since then I still live and sleep in my darkroom. As a photographer I was self-taught from the beginning." (Landshoff, 1939/40, 283.) In 1933, he fled to Paris due to increasing racist persecution and lived there until 1939. After being drafted into the Foreign Legion in Sidi Bel Abbès, Algeria (1939–1940), he finally managed to emigrate with his wife Ursula Nothmann from Marseille on the ship S.S. Siboney to New York, where they arrived on 25 May, 1941.

As he had been obliged to leave all his photographic equipment and his camera in Paris, Landshoff had to restart his photographic career from scratch in New York. Only one year after his arrival, however, thanks to his experience as a fashion photographer with Vogue in Paris, he was able to obtain work with such renowned magazines as Harper's Bazaar (1942–1946) and Mademoiselle (1947–1960). Little information is available about his wife Ursula Landshoff. She worked as a book illustrator. However, it is not known how her work and career progressed in exile in New York. Book illustrations were for example for If I had a Lion by Liesel Moak Skorten (Harper & Row, 1967), Daisy and the Stormy Nigh (Bradbury Press, 1970) and Okay Good Dog (Harper & Row, 1978).

Landshoff's first photographs of New York are three infrared images which he took from a higher perspective, looking down on the cityscape. In one image, the view of the city is flanked on either side by highrise buildings, the building on the left being the Rockefeller Center and the one on the right, St. Patrick’s Cathedral. By focussing and cutting the two buildings at the top and the sides Landshoff emphasised the impressive height of these two landmarks while focusing on the architectural style of New York during the 1940s, a mix of tradition and modernism. The high contrast black and white tone range and the clear view, achieved by the infrared filter, intensify the focus on the contrasting architectural styles and the staggering of the buildings. Landshoff had already experimented in Paris with infrared film and explained the technique in Autograph (Landshoff, 1939/40, 296–308). To this end, from the 1940s on, he used photographic paper characterised by a highly differentiated spectrum of tonal values. He usually used a 6 cm x 6 cm Rolleiflex or 6 cm x 9 cm medium format camera, like the one that appears in his self-portrait of 1942.

Although this was his only infrared photograph, the New York cityscape found its way into his fashion and portrait photographs, which he continued to shoot outdoors. For example, he took pictures on the roof terrace of Saks (of the luxury department store chain) on Fifth Avenue, where the models were framed by towering skyscrapers, as well as in Central Park, in front of the Public Library and at Bronx Zoo. Other emigrants working for the department store Saks, where for example the German émigré photographer Ruth Bernhard with commissioned work or the Ukraine illustrator Vladimir Bobritsky (Bobri) for advertisements.

In addition to urban staging in outdoor spaces, as fashion photographer for Harper’s Bazaar and Harper's Junior Bazaar (1942–1946) Landshoff also attempted to produce a new kind of fashion portrait, producing photographs that emphasised spontaneity and movement and stood in contrast to the conventional rigid portrait photographs taken in a studio. This development was encouraged by the Russian émigré graphic and set designer Alexey Brodovitch who, as art director, revamped the appearance of Harper’s Bazaar with new design, typography and use of photographs. Landshoff's high level of technical skill also led him to being commissioned to develop the prints for Ballet (J. J. Augustin, 1945), Brodovitch's photobook whose experimental dance photographs inspired Landshoff's own photographs of the Ballet Russe de Monte Carlo, directed by émigré George Balanchine in New York in 1946.

Besides these images, Landshoff also created a huge and impressive body of work of portrait photographs of emigrated artists, writers and intellectuals during the 1940s and into the 1960s. All of the portraits can be viewed in the digital collection of Deutsche Fotothek. Landshoff photographed his subjects either in their studios, gallery spaces, or in some private setting to obtain a holistic portrait that included attributes of their profession and artistic work. Examples include: the Surrealist scene in Peggy Guggenheim's townhouse (51st Street); Max Osborn in the Wildenstein Gallery; and Ossip Zadkine in his studio. This direct connection with the sitter's artistic work can also be found in the unique series of photographic portraits Landshoff produced of his emigrated European and American colleagues from 1942. In the same year, in 1942, he was part of the group and interdisciplinary exhibition 20th century portraits at the Museum of Modern Art, where two photographs of Leonora Carrington and Max Ernst were presented among other émigré artists and photographers as for example Lotte Jacobi.
Likewise, his portraits of fellow photographers show them with their cameras in a setting that reflects their profession. Among the emigrated photographers he photographed were Alfred Eisenstaedt, Martin Munkacsi, Robert Frank, George Hoyningen-Huene, Andreas Feininger, Lisette Model, Lucien Vogel, Fritz Goro (the husband of Carola Gregor), André Kértész, Herbert Matter, Horst P. Horst, Erwin Blumenfeld, Alexey Brodovitch, Roman Vishniac, Nina Leen, Maurice Tabard, Georg Karger.
Landshoff’s elevated understanding of technique and his profound photographic knowledge allowed him to publish in several photo magazines such as Minicam and Commercial Camera, which, in close cooperation with Eastman Kodak, were aimed at professional photographers and presented the latest photographic developments and techniques, including colour film from the 1950s onward.