The Power of aIM: calibrated color management for the entire workflow
David Long
Imaging Scientist, Eastman Kodak Company
Almost all major motion picture productions today face the challenge of overcoming mis-managed color reproduction across the full workflow. And at the heart of the problem lie the very same technologies modern filmmakers have embraced to improve production efficiency and enhance creative vision. As the world of feature film post-production has migrated from the tried and true standards of print film dailies and optical color decisions and effects to a video and data-centric model for rushes and digital intermediate, color management has gotten a little lost in the shuffle.
In the days when the 'look' of a movie was placed in the skilled hands of a master color timer and the Director of Photography, filmmakers could count on the color consistency and reliability of motion picture intermediate and print films to translate common color decisions from dailies to conformed edits and answer prints to finished exhibition release prints. But today, dailies and edits are derived from video scans of the footage produced during each shooting day. And anyone who has sat through a viewing of a pristine answer print and the master video transfer of the same movie knows that they often do not look the same. The issues include equipment capability and historical calibration. In addition, most video colorists who produce dailies today didn't grow up color-timing film prints and so the look of film transferred to video has only small correlation to the old standby of camera negative imaged onto print film. Add in video's limitations relative to matching print film for color gamut and dynamic range and you've got some challenges if you hope to exhibit your finished movie on a film projector. Further, the newly ubiquitous world of digital intermediate adds two more pieces of equipment that the guys in the good ol' days never had to worry about - the film scanner and the film recorder. You better believe that these two can do some damage to your color consistency, too.
The good news is that solutions exist, and steps can be taken to properly calibrate equipment and viewing environments. Digital intermediate provides nearly endless possibilities for shaping the look and feel of your movie. The guys in the DI lab can do things to your pictures that would make print color timers a few lights green with envy. The secret then is to maintain the power and flexibility of the video and data worlds, as well as to base the workflows in an architecture that provides a common color experience across multiple stages.
One such solution is LaserPacific's accurateIMAGETM (aIM) system, a seamless postproduction process that calibrates, connects and integrates all devices used for displaying images in various digital formats. It is utilized on set and for dailies, previews, the digital intermediate and distribution. The system is designed to faithfully emulate a project's look created by cinematographers in collaboration with their directors throughout every step of post-production. The aIM process also applies any color decisions or changes made during the early stages of the project to subsequent steps in the workflow. This eliminates the need to start over and recreate a look that had been previously dialed in.
aIM was developed in response to requests and suggestions made by cinematographers and other filmmakers. The process incorporates proprietary Kodak color science coupled with innovative LaserPacific technology. It also supports the Color Decision List (CDL) developed by the American Society of Cinematographer's Technology Committee, which allows color decisions made on set to transfer easier and more accurately to the next level, and all the way through to color correction and final release.
In the post-production laboratory, aIM takes advantage of film dye spectral characterizations and advanced color transforms to insure all telecines and data scanners used on a project are reproducing the same raw color information on each frame. The basis for the calibration is printing density, a metric that describes how a print film will see the dye amounts on the camera negative film. Printing density is especially useful in the data world as it provides a mathematical analog to the photochemical processes found in the traditional optical printing world. Thus the image is digitally encoded in a format that is completely translatable to optical printing steps, something very handy for when it comes time to actually record the data back onto film for replication and distribution. Further the Kodak CINEON or DPX data file formats used quite commonly in the industry already provide a workspace supporting 10-bit log printing density information.
With video telecines and data scanners producing perfectly color-matched raw image frames, the next step is to enforce a common color manipulation language. This comes in the form of the ASC's CDL where color decisions are summarized into tidy standard mathematical expressions. These decisions specifically take advantage of color corrections already commonly understood in traditional and digital post-production processes, including printer lights, lift, gamma, gain, and saturation controls. With color choices resolved to mathematical expressions, the raw scanned image can be floated to various pieces of color correction equipment where the two pieces are combined prior to viewing.
The final step is to provide proper emulation of the ultimate master viewing display, the projected piece of print film. Prior to being rendered to prints, the images are likely to be viewed on many different kinds of computer monitors, video monitors or digital projectors throughout the course of dailies and post-production. Each has its own unique color characteristics but each can be calibrated and characterized through 3D look-up table (3DLUT) image processing to render the appearance of the printed image. Thus anyone interacting with images in the digital realm will see the proper look of the project as referenced to the ultimate optical print.
At its heart, the aIM process is designed to emulate the consistency and reliability of optical printing workflows. The cinematographer documents a range of set ups during production with digital stills, which he or she manipulates with a personal computer to fine tune looks. The telecine colorist uses the cinematographer's still images as a roadmap for creating digital dailies. An aIM DailiesPlayer is used to view dailies with an aIM digital projector. All devices used during the process are calibrated.
The images are encrypted for security and a proprietary 3DLUT automatically adjusts the projected images to mimic film projection. The cinematographer can make adjustments in color balance using standard printer light controls which mimic film timing. His or her changes are exported to a CDL that is integrated into the workflow and used as the starting point for digital previews and DI timing.
By implementing calibrated scanning, calibrated color manipulation and calibrated viewing environments, LaserPacific's aIM system ensures the integrity of a controlled workflow from beginning to end. This new process delivers predictable visuals so that collaborators on a project see images at every step of the post process the same way audiences will see them in the theater.
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