The Dhoom Tanna Song in Om Shanti Om was to present Deepika Padukone as the "The Dreamy Girl - Shantipriya" (a popular heroine of 70's). To make the script more authentic she was to be shown acting alongside and romancing yesteryears legendary actors like Sunil Dutt, Rajesh Khanna and Jeetendra. It was impossible to shoot the song sequence with actual legendary actors as Rajesh Khanna & Jeetentra and Sunil Dutt is no more with us. This presented a major challenge which was solved by some extremely innovative use of VFX techniques.

The director Farah Khan wanted the song to have a 70's look so she selected footage from many old movies and handed them over to the team at Redchillies.vfx for short listing those which would fit their requirements.

Step 1:
While short listing the footage that could be used in the song, the team had to keep in mind that the selected scenes should have no lip movements by the male actors & the shots were with complicated camera moves and have some eye & body contact. Accordingly scenes from three songs were finalized from the movies Amrapali (1966) starring Sunil Dutt and Vaijantimala, Sacha Jhutta (1970) starring Rajesh Khanna and Mumtaz and Jay-Vijay (1977) starring Jeetendra and Jayashri T.

Then the team had to locate the original prints and negatives of the films they had selected.

Step 2:
The original footage were nearly 30 years old and hence not in the best condition. They had to be scanned and carefully restored. These footages included many scratches, a lot of grains, dust and color patches that was then cleaned up to the best quality on the computers.

Step 3:
The VFX team of Red Chillies used the *ROTOSCOPING technique. They rotoscoped the veteran actors from the old footage. These rotoscoped footages were then composited with a new background and with Deepika Padukone as Shantipriya of those times.
(*ROTOSCOPING refers to the technique of manually creating a matte for an element on a live action plate so it may be composited over another background.)

Step 4:
The Red Chillies team then had to design a new set matching one in the footage keeping in mind the camera angles and lighting. Also Deepika's costumes were matched with the yesteryear actresses to enhance her 70's look.

Step 5:
The next and the most important part was to establish a proper eye & body contact between Deepika Padukone and the veteran actors.

VFX teams made this challenging task a great success by making Deepika dance with dummies wearing CROMA suit to match every pose of hers to poses of the veteran actors. Things to note were the eye contact between the actors, physical touch, lighting continuity, perspective matching, skin tones matching and color matching.

In the song sequence of Deepika with Rajesh Khanna no dummies were used as the camera rotated around Rajesh Khanna, instead VFX team used a wire for Deepika's eye contact and a rod covered with green cloth to represent Rajesh Khanna's shoulder height.

The major technical input in the song was the use of some state of the art equipment which enabled the mixing of the rotoscoped images with the live shoot on the monitor in real time. This helped the team in matching camera angles of the live CROMA sequences with Deepika and the old footages at the time of the live shoot, making it more precise and lifelike added Keitan.

Step 6:

The cuts of the veteran actors from the old footage were then pasted with the CROMA takes of Deepika alongwith the background and the output was the amazing song sequence of Dhoon Tanna where Deepika was seen romancing the yesteryear biggies utmost ease. (This process of putting the shots together is technically called compositing)

But to give that feel of 70's there were other factors as well that had to be taken care off like color correction and texture. Previously it was decided to add scratches for the retro era look, but later the scratches were replaced by grains.

The shadow matching was also a crucial parameter which had to be considered for the Rajesh Khanna sequence, because it had Mumtaz's shadow falling over Rajesh Khanna's back. Hence the timing of Mumtaz shadow falling on Rajesh Khanna' s back had to be matched with Deepika's timing of going behind him. And the interesting fact is, as Arjun puts it, "The shadows were never created but matched."

Pinch :

The pinching sequence of Deepika and Jeetendra was shot with a dummy wearing a blue suit which was matched with the original suit worn by Jeetendra in the movie Jay-Vijay. Later, only the pinch was rotoscoped and composited with the final sequence.

*In VFX industry the term ROTOSCOPING refers to the technique of manually creating a matte for an element on a live action plate so it may be composited over another background.