Working with ARRIRAW

Log C to Rec 709

When ARRIRAW data is processed for post production, the output usually will be a Log C image to retain as much information as possible. Since Log C images look flat with desaturated colors on a regular video monitor, the footage needs to be output in Rec 709 video color space. This image conversion can be applied by using a 3 dimensional look up table (3D LUT) on the Log C material.

Generating Dailies
Material that was shot with the ALEXA set to Rec 709 color processing does not require proxies to be created as current playback and editing systems can handle material in HD resolution without problem.

Material that was shot with the ALEXA set to Log C color processing, on the other hand, needs to be converted to Rec 709 video to display correctly. Viewed on a regular video monitor, Log C images look flat with desaturated colors. In order to get a grayscale characteristic and color reproduction that is more pleasing to the eye, the images have to be tone-mapped and transformed into the target color space. This image conversion can be applied by using a 3 dimensional look up table (3D LUT) on the Log C material.



There are many tools that can be used to perform a Log C to Video conversion for dailies. Many applications will render out the camera material with applied 3D LUT conversions. Some applications, like the recently introduced Final Cut Pro X from Apple, can perform the conversion in realtime as the material is played back, so the editor can work directly on the original camera material.

Note:
 Final Cut Pro X’s realtime conversion requires an FXPlugin such as Pomfort's Alexa Look2Video, available at www.pomfort.com.

ARRI LUT Generator
As most of the tools use their own notation for look up tables, ARRI offers the conversion LUTs through the online ARRI LUT Generator, which can create over a dozen different LUT formats.

When dailies are going to be color timed, the colorist may prefer using a photometric conversion LUT as he or she will use just this one LUT for all shots and perform adjustments to the black and white levels anyway. An example of LUT generator settings for color-corrected dailies are shown below. For an automated dailies process, the normalized LUTs must be used in order to compensate for the different ASA settings on the camera.

If ARRI Look Files were created and used during the shoot, they can also be used with the ARRI LUT Generator to create 3D LUTs that include look file adjustments (Preset "Look"). This will allow the creation of Dailies including the intended look from the DP.