ARRI ALEXA post, part 2

by Oliver Peters

Post Workflow – Apple Final Cut Pro

Posting ARRI ALEXA’s ProRes clips is going to follow many of the established workflows. The fact that it’s a new camera doesn’t really make much difference. The camera generates direct-to-edit ProRes media with embedded timecode and reel IDs. These are self-contained files without a folder hierarchy to mess you up, like with P2 or XDCAM. These media files are immediately ready to edit with most modern NLEs, including Apple Final Cut Pro 7, Adobe Premiere Pro CS5 and Avid Media Composer 5 (via AMA). Assuming that these camera clips are intended as the master files, then “best practices” for tapeless workflows need to be followed to archive and protect the media. These files are your “electronic negative”.

You could, of course, immediately edit natively with these clips, but instead, I’m going to lay out an offline-online workflow using ARRI ALEXA clips. Since these master clips might be ProRes 4444 or ProRes (HQ), many editors would rather deal with smaller proxy editing files during the creative, rough cutting phase of a project.

For the sake of this exercise, I’m going to assume that the files are recorded using the ALEXA Log C profile. This yields a low-contrast, “flat” image designed to preserve dynamic range and offer optimum grading latitude. It’s a wonderful alternative to true camera raw recording, but adds a few considerations for post.

Step 1. Clone your media files for protection. Standard archiving solutions include LTO data tape, redundant copies on hard drive or burning media to Blu-ray discs (BR-ROM). Here is also a step-by-step guide from Abel Cine Tech about how to offload the cards for FCP editing.

Step 2. Import the camera masters (ProRes HQ or ProRes 4444) into an FCP project.

Step 3. Drag-and-drop all of your clips to a new sequence. Apply Nick Shaw’s custom ALEXA LUTs to the timeline clips. This is an FxScript FCP plug-in with an optional burn-in window for text and timecode. Use the version of the filter that matches the exposure index to which the camera was set during recording. Now select all the clips in the timeline and drag them to a new, empty bin. This will create subclips with the embedded plug-in (LUT + burn-in).

Step 4. Set up a Batch Export of these subclips. Change the export settings to a different codec, such as ProRes 422 (Proxy), DVCPROHD or anamorphic DV. The exported clips will now become your editing proxy media.

Step 5. Create a new FCP project (optional) and import the folder of exported clips. These will become your working clips for the rough cut. These will have the LUT and burn-in data “baked” into the file.

Step 6. Edit as you normally would until the cut is approved and locked.

Step 7. When the cut is locked, create a new FCP project (optional) and copy the sequence for the locked cut to the new project. Make the sequence clips independent and reconnect the files to the original camera master media. Of course, these clips no longer have the LUT or burn-in applied. Change the sequence settings to match the desired final quality. Adjust any graphics, images and text as needed. Use “send to Color” to move the FCP timeline into Color for final grading.

Step 8. Follow a standard Color grading routine for the sequence. Since there is no corresponding Color LUT for ALEXA files, yet, you will have to establish the correct base look in Color before adding any additional grading. Once the grading is done, render and send back to FCP.

I would recommend, setting a basic conversion grade in Color’s Primary In room that can be applied to all clips. This corrects the Log C profile. Then use the Secondary windows as full-screen “adjustment layers” for all of your normal grading tasks. An alternate approach is to use the Auto Balance control in the Primary In room. I don’t usually think much of such automatics, but it seemed to do a  good job with the ALEXA Log C clips that I tested. Apply it first, which changes the lift/gamma/gain values in the Primary – Advanced tab. Then alter the Primary – Basic saturation value to 1.5. Now you have a good starting point and can still use the curves and hue offset controls (“color wheels”) in the Primary room as you normally would.

Click on the image for an enlarged view. (Alexa clip courtesy of ARRI.)

Remember, that you are not applying a true LUT, since the adjustments you are making – even the automatic ones – are based on the levels for the frame on which you are parked. If a shot moves from bright sun to shade, then setting Auto Balance for the bright sunlit segment will cause the shaded portion to have crushed blacks, as well as the other way around. Be prepared to tweak as needed.

ARRI Digital will soon post a page with a LUTs Generator, which might alter this workflow in the future. Also check out ARRI-specific products at GlueTools.

©2010 Oliver Peters