After meeting Ike & Tina Turner he began photographing Bob Dylan and served as John Lennon's personal photographer during his time in New York City in 1971. Gruen is best known for his photograph of Lennon wearing a New York City T-shirt. Other notable celebrities and rock bands photographed by Gruen include the New York Dolls, The Clash, Ramones, Sex Pistols, Patti Smith Group, Blondie, Led Zeppelin, The Who, David Bowie, Elton John, Aerosmith, Kiss, Alice Cooper, Courtney Love and Green Day.