[3] Born to Punjabi Hindu parents in Gurdaspur in Punjab, Mahajan graduated in a physics from Panjab University, Chandigarh.

Thereafter, he joined the Film and Television Institute of India (FTII) and graduated with a diploma in Motion Picture Photography in 1966 with a gold medal.

[4] Prior to this, while still at FTII, he had shot, Shahani's avant garde graduation film, The Glass Pane (1966).

[2][4] This paved way for lifelong collaboration, as he went to shoot many films with Sen, including, Interview (1971), Calcutta 71 (1972), Padatik (1973), Chorus (1974), Mrigayaa (1976), Oka Oori Katha (1977), Ek Din Pratidin (1979), Akaler Sandhane (1980), Chalchitra (1981), Kharij (1982), Khandhar (1983) Ek Din Achanak (1988).

[5] Another director he worked extensively with was Basu Chatterjee; they had collaborated in films such as Piya Ka Ghar (1971), Rajnigandha (1974), Chhoti Si Baat (1975), Chitchor (1976), Swami (1977) and Manzil (1979).