Real Steel: How To

http://www.fxguide.com/fxpodcasts/fxpodcast-real-steel/

A highlight from the bottom.

Stage 7: Have great compositors

DD used a similar multi-pass compositing approach as it had done with its Makebot Nuke plug-in for I, Robot. But as the Real Steelcharacters had no real translucency, the process was easier, although artists still did a multi-pass approach as a multi-channel OpenEXR.

Compositing has certain key tasks, such as:

• match the black levels

•match the highlights

• balance the mid tones match the softness, motion blur and atmospheric conditions that integrate a shot

• allow light wrap

• match lens curvature and properties.

But, as you can imagine from the company that gave birth to Nuke, the DD compositors did a lot more than just standard multi-pass compositing.  For example, in the end stadium shots there was a need for massively large stadium crowds. DD's composite team delivered live action real stadium crowds, yet they never had more than 500 extras on set. One location in Detroit was used as two locations in the film.