last updated 16 Mar 2008

DI - Recording

Digital Intermediates - recording back to film

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After all the grading magic is over you still need to show it to the public.
Recording back to film represents the final challenge in DI.

Back to film

After all the stages of DI are over, all effects and graphics shots inserted, sound mixed and ready. And everyone has checked it all matches. Finally you need to put it back to film so film prints can be made and shown in theatres.

At this time, the film exists on a hard disk. a large disk array. Its normally a file sequence. a .dpx file sequence. Most likely sitting in 5-9 folders one folder for each reel. As many as 30,000 files can go into a reel and a film can have anywhere between 150,000 to 250,000 frames.

This file sequence is then sent to a 'film recorder'. An example of a film recorder is Arrilaser made by Arri which also makes film cameras. Even Imagica, Celco, Lasergraphics and Cinevation make film recorders.

Different technologies are used to write the image to film.

In an Arrilaser, as the name suggests, a laser beam, or rather three laser beams red, blue, and green lasers actually scan the film line by line frame by frame. Drawing a frame at a time. Arrilaser takes about 2 sec. per frame. So a normal Hindi film is recorded in 5-8 days.

Other recordes use LEDs or CRTs to write to film. But the principle is the same. DPX files are opened one by one, frames and/or resized if necessary, then light (laser, LED, or CRT) is used write to film, frame by frame.

Cinevator from Cinevation, uses a slightly different approach. This recorder uses DLP chips to create the entire frame image. And LEDs to illuminate the DLPs. This permits the Cinevator to write images extremely fast. In fact Cinevator records film at a full 24 fps. Making it the fastest film recorder for DI.



What resolution

Just as scanning and grading can be done at different resolutions, so can recording. The recording system either takes the DI files and records them 1:1, or does scaling to fit the image to film. But it is either HD (1920x1080), 2k (2048x1536), or 4k (4096x3112).

Writing speed is dependent on resolution. 4k recording takes longer than 2k which takes longer than HD.






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