Blog series Part 3

In-camera grading: Custom color management with ALEXA 35 and Livegrade 

in-camera grading Alexa 35 Livegrade custom color management

Are you ready for the final technical deep dive to wrap up our content series on in-camera grading? Before jumping into today’s topic, let’s quickly recap what we’ve covered so far: In Part 1, we introduced the general concept of in-camera grading with Livegrade and explored some of its key benefits. In Part 2, we then looked at the actual workflow, taking a hypothetical setup with the ARRI ALEXA 35 as an example. In that example, we used Livegrade to adjust the creative elements (CDL+CMT) of the underlying look file (ALF4) while the technical components for colorspace conversions (DRTs) remained untouched. 

But what happens when you want to grade in-camera, but the default display rendering transforms (DRTs) your camera provides don’t align with production requirements? Or when you’re asked to work with a distinct color management specification, like ACES? Don’t worry, we got you! In this article, we’ll focus again on an in-camera grading workflow with the Alexa 35 and Livegrade but use custom color management instead of ARRI’s standardized DRTs. 

Before we begin, it’s important to highlight that converting LogC4 to a specific output colorspace using custom color management carries higher risks than relying on default DRTs. As the creator of custom DRTs, you bear full responsibility for the accuracy of the workflow and must, therefore, be absolutely confident in your skills. Only choose this approach after close consultation with the production team.

Understanding ALF4c looks

As in Part 2, our workflow discussion starts with explaining the underlying look file, as we need to understand it before moving on. The look file that’s used with the custom color management options of the Alexa 35 is called ALF4c. The illustration below displays the core elements of ALF4c, which may already look familiar to you: 

In-camera grading: Custom color management with ALEXA 35 and Livegrade 
Fig. 1: Components of an ALF4c look for custom color management

We used a similar illustration in Part 2 since both ALF4 and ALF4c look files share the same core elements: CDL, CMT, DRT SDR, and DRT HDR. However, the key difference is that the DRTs used in ALF4c are not those configured in the camera. Instead, they incorporate custom 3D LUTs provided by the user. 

Understanding your options

As mentioned in the introduction, there are two main use cases for working with custom DRTs, which we will both cover in this article and outline what’s possible with Livegrade: 

1. Customizing display rendering transforms 
You may want to replace the display rendering transforms for technical or creative reasons. When taking this approach with Livegrade, it will still be possible to edit the CDL and CMT components live. All the advantages of in-camera grading thus remain available to you, including dual-monitoring via the camera. 

2. Using custom color pipelines
It’s also possible to use a completely custom color pipeline designed in Livegrade. You can tailor it to the specific needs of your workflow regardless of the scheme specified by the look format. For example, you can set up an ACES workflow while still benefiting from all the advantages of in-camera grading. 

Use case 1: Customizing display rendering transforms

The need for customized display rendering transforms can arise from several reasons, both creative and workflow-related. For example, the lead colorist may have a specific vision for how the display rendering should be handled, like wanting the DRT to place HDR brightness and colors differently than possible with the manufacturer’s LUTs. Or the production decides on a certain target colorspace or a maximum NIT level that is not provided by the manufacturer’s LUTs. Whatever sparked the decision, let’s assume you are on set and want to grade your in-camera look with customized display rendering transforms. 

Step by step: How to create an ALF4c look and grade it live

Using Livegrade to work with an ALF4c and custom DRTs is quite similar to working with an ALF4. You grade the CDL and CMT parts of the look and leave it to the camera to select the suitable custom DRT. That way, it is still possible to flexibly decide on the camera side which SDI output of the camera should show which colorspace: HDR or SDR. We will now walk you through each step of the workflow so that you end up with a detailed overview of the following: 

  • How to create an ALF4c look with custom DRTs using the ARRI Reference Tool
  • How to adjust that look with Livegrade by adding a film emulation look and adjusting CDL values 
  • How to extract the look in Silverstack 

In our hypothetical scenario, we assume you already received custom DRTs for SDR and HDR as 3D LUT. Usually, they will be provided by either the production or the lead colorist. If you want to work through the example yourself, please also prepare the following: Make sure you are using the latest version of Livegrade Pro or Studio and have the ARRI Reference Tool installed. Your Alexa 35 needs to run at least on SUP 1.2.1 or later. So with all preparations taken care of, let’s begin! 

Step 1: Create an ALF4c

The first step is to create an ALF4c in the ARRI Reference Tool. To do so: 

  • Open the ARRI Reference Tool and go to the „Look“section. 
  • At the bottom, select „Custom Color Management“
  • Click on the „DRT“ part of your ALF4c look.
  • Load the3D LUTs for SDR and HDR.
  • Select the „Target Color Space“ for SDR and HDR, respectively. 
  • Click on „Save Look File“, give your look a name, and hit save. 
In-camera grading: Custom color management with ALEXA 35 and Livegrade 
Fig. 2: Creating an ALF4c in the ARRI Reference Tool

Example:

  • Load „Custom_DRT_SDR_Rec709.cube with Target Color SpaceRec 709-D65 as DRT for SDR. 
  • Load „Custom_DRT_HDR_Rec2100_PQ_1000nits.cube with Target Color Space „Rec 2100 / PQ as DRT for HDR.
  • Save your look as „Example_CustomDRTs.alf4c“. 

Step 2: Load ALF4c into the camera

Next, load the saved file into the camera: 

  • Attach the camera’s USB drive to your computer. 
  • Copy and paste the look file into the look files folder on the USB drive.
  • Attach the USB drive to the camera.
  • Import the look file and select it in the camera menu. 
In-camera grading: Custom color management with ALEXA 35 and Livegrade 
Fig. 3: ARRI Alexa 35 look menu

Step 3: Prepare the camera

To enable the communication with Livegrade, please check the following:

  • Network connection: To exchange look information with Livegrade, the camera needs to have a working network connection with the computer that’s running Livegrade.
  • Enable CAP: To connect Livegrade to the camera, you have to enable the Camera Access Protocol (CAP) in the ARRI camera’s menu at „System > Camera Access Protocol“. You can also set a CAP server password there to protect access to the camera.

Step 4: Add camera in CDL+CMT mode

After your camera is set up, switch to Livegrade and add your camera to CDL+CMT look control mode: 

  • Add the camera to one of your slots using the „Add ARRI Camera“ dialog in the device manager. 
  • Activate “Enable framegrab“.
  • Set „Look Control“ to “CDL + CMT“ within the advanced color pipeline options. 
In-camera grading: Custom color management with ALEXA 35 and Livegrade 
Fig. 4: Setting look control to CDL+CMT mode in Livegrade’s device manager

Step 5: Set up the look in Livegrade

As you already know from Part 2, grading an Alexa 35 in CDL + CMT look control mode will adjust the in-camera look as follows:

  • All of your CDL and saturation adjustments that you make within the ARRI CAP compatible mode will be mathematically merged and then sent as one CDL value set to the camera’s look.
  • All Log-to-Log LUTs, curve adjustments, and other LUT-based nodes within your grade will be merged into one single 3D LUT, which will be sent as CMT to the camera’s look.
  • The DRTs in your camera won’t be changed via Livegrade. They will be managed by the camera, although you’ve set them to customized 3D LUTs by loading an ALF4c file into the camera before. Depending on the chosen SDI colorspace in the camera, either the custom DRT SDR or the custom DRT HDR will be used to transform your image to a display referred colorspace.
In-camera grading: Custom color management with ALEXA 35 and Livegrade 
Fig. 5: Overview of an ALF4c look with custom DRTs

This means that the last LUT node in Livegrade won’t be sent to the camera, as it will be applied in-camera anyway. However, if you are working with a LogC4-image source like a frame grab in Livegrade and want to use your Livegrade looks to be applied to original camera footage at a later point (e.g., to share stills), you should set the last LUT node with the exact same transform that has been set in ALF4c look file. The recommended best practice in this regard is to use either the DRT SDR or DRT HDR as your last LUT node, depending on the colorspace in which you want to pass your looks and stills from Livegrade on to others. Keep in mind: The whole look, including both DRTs, will be saved with each recording anyway.

Example:

  • Use the first CDL node to warm up the scene.
  • Load 3110 Film A.cube from ARRI’s LogC4 look library into your 3D LUT node “CMT” to add a filmic look to your image.
  • Load „Custom_DRT_SDR_Rec709.cubeinto your last LUT node “DRT”, to get the same image in Livegrade as on your graded SDR camera output and to hand over your looks and stills from Livegrade to other departments in SDR.

Finally, check if everything is set up correctly: 

  • Request a frame grab via „Slots > Refresh Framegrab of Current Device“.
  • Compare the graded frame grab in Livegrade with the graded output of the camera.
  • Do they match? Then you are good to go!
  • If they look different, you should make sure that your ethernet connection to the camera is stable and that the last LUT node “DRT” in Livegrade was set to convert to the same colorspace as the selected SDI colorspace in the camera.
In-camera grading: Custom color management with ALEXA 35 and Livegrade 
Fig. 6: Working with custom DRTs in Livegrade

Step 6: Extract the look from recorded clips in Silverstack

Just like discussed in Part 2, the current look that the camera outputs will always be saved in the clip’s file header and can be extracted in Silverstack. The look from the recorded clip will then unfold in its single parts represented by the individual nodes:

  • CDL: will contain all CDL adjustments 
  • Saturation: will contain all Saturation adjustments
  • CMT: will contain all LUTs and Curve adjustments (except the last LUT node) merged into one single 3D LUT file
  • SDR: will contain the custom DRT SDR you’ve loaded into the custom ALF4c file
  • HDR: will contain the custom DRT HDR you’ve loaded into the custom ALF4c file

In the context of our discussed example, the look should unfold as follows:

  • CDL: should contain an adjustment to warm up the image
  • Saturation: will be set to neutral
  • CMT: should contain „3110 Film A.cube“, which adds a filmic look to the image
  • SDR: should contain „Custom_DRT_SDR_Rec709.cub“
  • HDR: should contain „Custom_DRT_HDR_Rec2100_PQ_1000nits.cube“
In-camera grading: Custom color management with ALEXA 35 and Livegrade 
Fig. 7: Look with custom DRTs extracted in Silverstack

Use case 2: Using custom color pipelines

The decision to use a specific color management system for a production can be driven by various factors. For example, a production might use different camera types and require the film to be evaluated in different target colorspaces. It’s also possible that the post-production pipeline is optimized for a particular color management system, such as ACES. Whatever the reason, this section will guide you through how to use Livegrade to send any look pipeline to the ALEXA 35 and what considerations should be taken.

At the heart of this workflow is the new DRT-only look control mode, introduced with Livegrade 6.5. This mode makes it possible to use any grading mode and send the entire look as a 3D LUT into the DRT part of an ALF4c look. With this approach, you can, for example, work in an ACES look pipeline, output the graded image via the camera’s SDI ports or viewfinder, and save the look directly in the camera. At first glance, having these possibilities seems like ultimate freedom: No matter which input-, output- or creative- transforms happen in your look, it will be shown on your camera’s graded outputs and saved within each clip’s file header as 3D LUT. However, there are critical considerations to address before diving into an example of how to use the DRT-only mode to send an ACES look to the camera:

  1. Custom control of display rendering: In DRT-only mode, you are entirely responsible for the color management and control over the display rendering at the end of the pipeline. What you send to the camera via Livegrade will be displayed on the camera’s graded outputs and saved in the file header of each clip.
  2. DRT-only means that CDL and CMT will be neutral: In DRT-only mode, the look is saved as a single 3D LUT as DRT SDR and DRT HDR in the clip. An extracted DRT-only look, therefore, only contains a single 3D LUT that is saved identically in the DRT SDR and DRT HDR part of the look. If the separation between CDL, CMT, and DRT part is relevant in dailies grading (e.g., to view and build upon specific CDL values), look matching via ShotHub or a look export is necessary.
  3. One pipeline for one colorspace: The ALF4c look controlled in DRT-only mode contains a single color pipeline for a specific target colorspace – the one configured in Livegrade. This means that every graded output of the camera shows exactly this look and that it is only stored for this specific target colorspace. For example, if you send an HDR look to the camera but configure your camera’s SDI out for Rec.709, you will not receive a valid SDR image. Dual monitoring via the camera is therefore not possible. However, it can be achieved by introducing an additional LUT box controlled by Livegrade.
In-camera grading: Custom color management with ALEXA 35 and Livegrade 
Fig. 8: Overview of an ALF4c look in DRT-only mode

Step by step: How to grade a custom color pipeline in-camera

Now, we will walk you through each step of grading an Alexa 35 remotely with a custom color pipeline. To do so, we will use an ACES Rec.709 look as an example.

Step 1: Prepare the camera

To enable the communication with Livegrade, please check the following:

  • Network connection: To exchange look information with Livegrade, the camera needs to have a working network connection with the computer that’s running Livegrade.
  • Enable CAP: To connect Livegrade to the camera, you have to enable the Camera Access Protocol (CAP) in the ARRI camera’s menu at „System > Camera Access Protocol“. You can also set a CAP server password there to protect access to the camera.
  • Editable look selected in the camera: Before grading an ARRI camera, make sure that you have selected an editable look (e.g., by duplicating the default look) in your camera.

Example:

  • Duplicate the default look and name it „Example_DRTonly“.

Step 2: Add camera in DRT-only mode

After your camera is set up, switch to Livegrade and add your camera in DRT-only look control mode: 

  • Add the camera to one of your slots using the „Add ARRI Camera“ dialog in the device manager. 
  • Activate „Enable framegrab“.
  • Set „Look Control“ to “CDL + CMT“ within the advanced color pipeline options. 
  • Select the target colorspace of the look which you will send to the camera. 
  • Please note: In DRT-only mode, your look will only be valid for this single colorspace.
In-camera grading: Custom color management with ALEXA 35 and Livegrade 
Fig. 9: Setting look control to DRT-only mode in Livegrade’s device manager

Step 3: Set up an ACES look in Livegrade

Once you’ve added your camera as a device to your slot, you can begin creating your custom look pipeline. And by custom, we mean custom: There are basically no restraints in DRT-only mode; you can incorporate any grading mode and any node type you want. No matter what you do, all your grading will be baked into a 3D LUT and sent to the camera. 

Again, this might sound like a lot of freedom. However, keep in mind that some post-production workflows require viewing or building on all parts of the look pipeline that you graded live.

To ensure compatibility with post-production and to allow your looks to be passed on via ShotHub or exported in standard formats like CDLs, AMFs, or ALEs, it’s crucial to choose your grading mode and node configuration carefully.

Example:

  • Select the grading mode “ACES CDL Advanced”.
  • Select ARRI LogC4 as IDT.
  • Select Rec.709 100 nits as ODT.
  • Use the first CDL node to warm up the scene.
  • Use a curves node to retain details in the highlights and the blacks.

Finally, check if everything is set up correctly: 

  • Request a frame grab via „Slots > Refresh Framegrab of Current Device“.
  • Compare the graded frame grab in Livegrade with the graded output of the camera
  • Do they match? Then you are good to go!
  • If they look different, make sure that your ethernet connection to the camera is stable and that you chose an editable look in your camera.
In-camera grading: Custom color management with ALEXA 35 and Livegrade 
Fig. 10: Grading Alexa 35 in-camera with Livegrade using DRT-only mode

Step 4: Extract the look from recorded clips in Silverstack

In the case of DRT-only look control mode, CDL and CMT will be left neutral and the whole look will be represented as 3D LUT stored identically in the DRT SDR and DRT HDR part of the look. When extracting the look from the recorded clip it will unfold as follows:

  • CDL: will contain neutral CDL adjustments
  • Saturation: will contain neutral Saturation adjustments
  • CMT: will contain an identity LUT that does not alter the image
  • SDR: will contain your look as 3D LUT, including the ODT for Rec.709
  • HDR: will contain your look as 3D LUT, including the ODT for Rec.709

For our example, this means: 

  • CDL: should contain neutral CDL adjustments
  • Saturation: should contain neutral Saturation adjustments
  • CMT: should contain an identity LUT that does not alter the image
  • SDR: should contain a 3D LUT which represents the result of the graded ACES pipeline, including the ODT for Rec.709 
  • HDR: should contain a 3D LUT, which represents the result of the graded ACES pipeline, including the ODT for Rec.709
In-camera grading: Custom color management with ALEXA 35 and Livegrade 
Fig. 11: Extracted looks in Silverstack with DRT-only mode

Quick comparison: CDL+CMT vs. DRT-only

In-camera grading: Custom color management with ALEXA 35 and Livegrade 
Fig. 12: Comparison table: CDL+CMT vs. DRT-only mode

Conclusion

Across all three parts of this content series, we explored the possibilities of in-camera grading and specifically examined how Livegrade interacts with the ALEXA 35. As shown in Part 2, you can take the safe path of processing looks in the ARRI Color Management Pipeline, where standardized LUTs handle display rendering for various target formats. However, not all productions fit into this standardized workflow. When a custom color pipeline is required, you don’t have to forgo the benefits of in-camera grading, though. The ALEXA 35’s advanced custom color management options, combined with the latest innovations in Livegrade, enable productions to maintain the advantages of in-camera grading while tailoring the pipeline to specific creative or technical needs. 

The State-of-the-Art Digital Imaging System

Test Livegrade Studio with our free 10 day trial!

About the author
Lukas is a product manager for Pomfort’s on-set systems. Having worked as an assistant camera and finals colorist for several years, he combines on-set with post-production knowledge and has a keen eye on everything that helps creatives to realize their vision.
Kim
Natascha
Patrick
Lukas
Wanja
Franz
Elwin
Who is writing for you?

We are Pomfort's editorial team - a group of tech specialists, industry experts and communication professionals working across diverse technical and creative roles within the company. Together, we create engaging content for the global film production community, exploring the topics that matter most to them.

Stay up to Date
Pomfort Blog RSS Feed