An artificial intelligence grading option for editors and colorists
There are many low-cost software options for color correction and grading, but getting a stunning look is still down to the skill of a colorist. Why can’t modern artificial intelligence tools improve the color grading process? Colorist and color scientist Dado Valentic developed Colourlab Ai as just that solution. It’s a macOS product that’s a combination of a standalone application and companion plug-ins for Resolve, Premiere Pro, Final Cut Pro, and Pomfort Live Grade.
Colourlab Ai is comprised of two main functions – grading and show look creation. Most Premiere Pro and Final Cut Pro editors will be interested in either the basic Colourlab Ai Creator or the richer features of Colourlab Ai Pro. The Creator version offers all of the color matching and grading tools, plus links to Final Cut Pro and Premiere Pro. The Pro version adds advanced show look design, DaVinci Resolve and Pomfort Live Grade integration, SDI output, and Tangent panel support. These integrations differ slightly, due to the architecture of each host application.
Advanced color science and image processing
Colourlab Ai uses color management similar to Resolve or Baselight. The incoming clip is processed with an IDT (input device transform), color adjustments are applied within a working color space, and then it’s processed with an ODT (output device transform) – all in real-time. This enables support for a variety of cameras with different color science models (such as ARRI Log-C) and it allows for output based on different display color spaces, such as Rec 709, P3, or sRGB.
If you prefer to work directly with the Colourlab Ai application by itself – no problem. Import raw footage, color correct the clips, and then export rendered movie files with a baked in look. Or you can use the familiar roundtrip approach as you would with DaVinci Resolve. However, the difference in the Colourlab Ai roundtrip is that only color information moves back to the editing application without the need to render any new media.
The Colourlab Ai plug-in for Final Cut Pro or Premiere Pro reads the color information created by the Colourlab Ai application from an XML file used to transfer that data. A source effect is automatically applied to each clip with those color parameters. The settings are still editable inside Final Cut Pro (not Premiere Pro). If you want to modify any color parameter, simply uncheck the “Use Smart Match” button and adjust the sliders in the inspector. In fact, the Colourlab Ai plug-in for FCP is a full-featured grading effect and you could use it that way. Of course, that’s doing it the hard way!
The ability to hand off source clips to Final Cut Pro with color metadata attached is unique to Colourlab Ai. This is especially a game changer for DITs who deliver footage with a one-light grade to editors working in FCP. The fact that no media need be rendered also significantly speeds up the process.
A professional grading workflow with Final Cut Pro and Colourlab Ai
Thanks to Apple’s color science and media architecture, Final Cut Pro can be used as a professional color grading platform with the right third-party tools. CoreMelt (Chromatic) and Color Trix (Color Finale) are two examples of developers who have had success offering advanced tools, using floating panels within the Final Cut Pro interface. Colourlab Ai takes a different approach by offloading the grade to its own application, which has been designed specifically for this task.
My workflow test involved two passes – once for dailies (such as a one-light grade performed by a DIT on-set) and then again for the final grade of the locked cut. I could have simply sent the locked cut once to Colourlab Ai, but my intention was to test a workflow more common for feature films. Shot matching between different set-ups and camera types is the most time-consuming part of color grading. Colourlab Ai is intended to make that process more efficient by employing artificial intelligence.
Step one of the workflow is to assemble a stringout of all of your raw footage into a new FCP project (sequence). Then drag that project from FCP to the Colourlab Ai icon on the dock (Colourlab Ai has already been opened). The Colourlab Ai app will automatically determine some of the camera sources (like ARRI files) and apply the correct IDT. For any unknown camera, manually test the settings for different cameras or simply stick with a default Rec 709 IDT.
The Pro interface features three tabs – Grade, Timeline Intelligence, and Look Design. The top half of the Grade tab displays the viewer and reference images used for matching. Color wheels, printer light controls, scopes, and versions are in the bottom half. Scope choices include waveform, RGB parade, or vectorscope, but also EL Zones. Developed by Ed Lachman, ASC, the EL Zone System is a false color display with 15 colors to represent a 15-stop exposure range. The mid-point equates to the 18% grey standard.
AI-based shot matching forms the core
Colourlab Ai focuses on smart shot matching, either through its Auto-Color feature or by matching to a reference image. The application includes a variety of reference images, but you can also import your own, such as from Shotdeck. The big advance Colourlab Ai offers over other matching solutions is Color Tune. A small panel of thumbnails can be opened for any clip. Adjust correction parameters – brightness, contrast, density, etc – simply by stepping through incremental value changes. Click on a thumbnail to preview it in the viewer.
The truly unique aspect is that Color Tune lets you choose from eleven matching options. Maybe instead of a Smart model, you’d prefer to match based only on Balance or RGB or a Perceptual model. Step through the thumbnails and pick the look that’s right for the shot. Therefore, matching isn’t an opaque process. It can be optimized in a style more akin to adjusting photos than traditional video color correction.
Timeline Intelligence allows you to rearrange the sequence to group similar set-ups together. Once you do this, use matching to set a pleasing look for one shot. Select that shot as a “fingerprint.” Then select the rest of the shots in a group and match those to the fingerprinted reference shot. This automatically applies that grade to the rest. But, it’s not like adding a simple LUT to a clip or copy-and-pasting settings. Each shot is separately analyzed and matched based on the differences within each shot.
When you’re done going through all of the shots, right-click any clip and “push” the scene (the timeline) back to Final Cut Pro. This action uses FCPXML data to send the dailies clips back to Final Cut, now with the added Colourlab Ai effect containing the color parameters on each source clip.
Remember that Final Cut Pro automatically adds a LUT to certain camera clips, such as ARRI Alexa files recorded in Log-C. When your clips comes back in from Colourlab Ai, FCP may add a LUT on top of some camera files. You don’t want this, because Colourlab Ai has already made this adjustment with its IDT. If that happens, simply change the inspector LUT setting for that source file to “none.”
Lock the edit and create your final look
At this point you can edit with native camera clips that have a primary grade applied to them. No proxy media rendered by a DIT, hence a much faster turnaround and no extra media to take up drive space. Once you’ve locked the edit, it’s time for step two – the show look design for the final edit.
Drag the edited FCP project (new sequence with the graded clips) to the Colourlab Ai icon on the dock to send the edited sequence back to Colourlab Ai. All of the clips retain the color settings created earlier in the dailies grading session. However, this primary grade is just color metadata and can be altered. After any additional color tweaks, it’s time to move to Show Looks. Click through the show look examples and apply the one that fits best.
If you have multiple shots with the same look, apply a show look to the first one, copy it, and then apply that look to the rest of the selected clips. In most cases, you’ll have a different show look for various scenes within a film, but it’s also possible that a single show look would work through the entire film. So, experiment!
To modify a look or create your own, step into the Look Design tab (Pro version). Here you’ll find the Filmlab and Primary panels. Filmlab uses film stock emulation models and film’s subtractive color (CMY instead of RGB) for adjustments. Their film emulation is among the most convincing I’ve seen. You can select from a wide range of branded negative and print film stocks and then make contrast, saturation, and CMY color adjustments. The Primary panel gives you even more control over RGBCMY for the lift, gamma, and gain regions. Custom adjustments may be saved to create your own show looks. Once you’ve set a show look for all of your shots, push the sequence back to Final Cut Pro. Voila – a fully graded show and no superfluous media created in the process.
Colourlab Ai is a revolutionary tool based on a film-style approach to grading. Artificial intelligence models speed up the process, but you are always in control. Thanks to the ease of operation, you can get great results without Resolve’s complex node structure. You can always augment a shot with FCP’s own color tools for a power window or a vignette.
The application currently lacks a traditional undo/redo stack. Therefore, use the version history to experiment with settings and looks. Each time you generate a new match, such as with Auto-Color or using a reference image, a new version is automatically stored. If you want to iterate, then manually add a version at any waypoint if a new match isn’t involved – for example, when making color wheels adjustments. The version history displays a thumbnail for each version. Step through them to pick the one that suits you best.
If you are new to color correction, then Colourlab Ai might look daunting at first glance. Nevertheless, it’s deceptively easy to use. There are numerous tutorials available on the website, as well as directly accessible from the launch window. A 7-day free trial can be downloaded for you to dip your toes in the water. The artificial intelligence at the heart of Colourlab Ai will enable any editor to deliver professional grades.
©2022 Oliver Peters
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