DoP Sudeep Chatterjee (Padmaavat, Chak De India, Guzaarish)says the brief he received from Bhansali for this scene was that apart from looking grand and dramatic, it also had to look beautiful. But the shoot was complex one. Apart from lead actors Ranveer Singh and Deepika Padukone, there were countless junior artists, animals, etc who were also a part of the scene. Therefore, the scenes were shot in layers and later blended into one. In fact, the lead actors weren't even taken on location for the shoot. Their portions were shot in a studio.
This was done by first consulting the action department, the art department and Bhansali himself to create a conclusive storyboard. The storyboard was broken down and cellophane sheets were used for different layers – foreground, background, VFX, etc. Remember the iconic image of Ranveer Singh climbing over the heads of armoured men and an elephant, to behead a soldier? Chatterjee says they used a crane to shoot the moment and the elephant was added later.
Thus, separate parts were shot separately and location photography was reduced to 8-9 days. Major elements of the scene like the lighting, which is typically controlled on the set, was in this case worked on in post-production with the help of VFX. "I don't have that puritan frame of mind where 'everything has to be done on-set.' If the technology is available and it's helping me tell the story better, then I'd jump at it," says Chatterjee.
Watch his give a detailed breakdown of how the battle scenes were shot.