Mumbai, May 3 : National Award-winning filmmaker Sankalp Reddy shared that it was a seven-month phase of trial and error to nail the 1970s look for the upcoming spy thriller 'IB 71' starring Vidyut Jammwal. Set in 1971, the spy thriller based on real-life incidents. The film talks about how the Indian Intelligence Bureau in a secret mission, outwitted the entire enemy establishment and gave the armed forces the required advantages to win the 1971 Indo-Pak war. Describing his process of nailing the 70s look, Reddy said: "It was a sincere coordination between the production designer, art department, costume designer, and DOP. It was a 7-month phase of trial and error method." "We procured news articles from libraries in Delhi and Mumbai to flesh out the story. The right look for elements in a film like this is a gamble. You experiment extensively before finding something that fits just right. The colour palette was another area we spent a lot of time on." 'IB 71' is presented by Gulshan Kumar, T-Series Film and Reliance Entertainment. The Action Hero Films production stars Vidyut Jammwal, Anupam Kher and Vishal Jethwa in pivotal roles and is produced by Bhushan Kumar, Action Hero Films and Reliance Entertainment. Produced by Vidyut Jammwal and Abbas Sayyed, co-produced by Aditya Shastri, Aditya Chowksey and Shiv Chanana. The film is directed by national award winner Sankalp Reddy with the story by Aditya Shastri and the screenplay by Storyhouse Films LLP. The film is slated for a theatrical release on May 12. /IANS