During the planning stage, Dibakar, 44, told PTI, he had worried a lot about how to impart a retro look to his movie, as the city has transformed much with skyscrapers and huge shopping malls now proclaiming their presence.
"But as I began to explore the city's old quarters in the north and central part, I discovered a fascinating picture of old world charm complete with narrow lanes, old buildings, tram tracks and above all the unobtrusive bustle," he said.
Dibakar said that in the first leg of shooting he had used a lot of vintage cars of the 1920s like Austin and Rangers, horse-drawn carriages and old tram cars, thanks to the Calcutta Tramways Company.
"For scenes which may have references to present-day Kolkata, we will use DI technique while editing, but mostly they were real time ones," he said adding the unit would be back in a few months.
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He said that the Dalhousie Square part of the shooting was done to recreate the ambience of 1943 when the city was experiencing the first stirring of World War II and Byomkesh was passing through the area when a Red Cross charity drive was in progress.
The two British era trams, used in the shooting, were painted afresh with adverts of a hair oil and perfume adorning the cars which were popular among women of those days.
Sushant Singh Rajput will play Byomkesh Bakshi, the character immortalised by author Saradindu Bandyopadhyaya.
Dibakar has bought the rights of all 33 Byomkesh stories.