Monitor Based LUTs

Introduction

After monitor calibration is complete, we have to make sure we take advantage of its benefits in every possible software. Programs like Photoshop are color managed - they recognize both the monitor profile as well as the embedded profile in an image and using this information render correct a color representation. Thus, we can be sure that, when viewing an image through Photoshop, we will see the correct color.

Unfortunately, not every software is color managed. 3ds Max and Fusion, two of the main tools 3D artists use, are both color agnostic. As these programs weren't really developed for print purposes, no one has thought they will need to understand embedded image profiles. That's why they can only use our monitor profiles to interpret color - and that's not enough.

In a sense, we have to cheat these programs in one way or another. To do so we can generate a LUT (Look Up Table) based on our monitor profile - a sort of an artificial profile that will mimic what would usually be an embedded image color profile.

Generation

The process of generating these LUTs can be quite difficult to comprehend but, viewed in terms of what steps need to be undertaken, it is very simple. It has to be done for every monitor connected to your PC. Here's how to do it:

1. Open up the file called Calibration Chart - Nov 2014+.tif located in R:\02_ASSETS\0000_COLOR\_RESOURCES with Photoshop.

2. If an Embedded Profile Mismatch pop-up window shows make sure to select Use the embedded profile. If it doesn't, don't worry about it.

3. Go to Edit>Assign Profile select Profile and from the drop-down menu select the profile of the monitor for which you need to generate a LUT (For ex. BGWORKSTATION01_LEFT_010120).

4. With the file still open in Photoshop start 3D Lut Creator and click on the Image from PS button to load the image.

5. Select the Color chart grid tool and align the grid properly on top of the color chart image.

6. Set the proper settings for the Color chart grid tool - the type of the checker to X-Rite ColorChecker (Nov 2014+) and the type of correction to Curves + 3DLUT.

7. Press the Match button.

8. Now go back and change the correction type from Curves + Matrix to A/B and press Match again. The correction LUT has been created.

9. Save the LUT using the Save 3DLUT button. Save it as a .cube file in R:\02_ASSETS\0000_COLOR\ in the folder with the name of the machine. For the naming, use the exact same name as the color profile of the monitor (For ex. BGWORKSTATION01_LEFT_010120.cube).

Below you can see a short video demonstrating the whole process.

Usage

After the LUTs have been created, they are going to be used only for preview purposes. Let's see how to set them up:

3ds Max & V-Ray

3ds Max offers very poor LUT support, while V-Ray does have a bit better integration where the LUTs are loaded directly into the V-Ray Frame Buffer. To load an LUT enable Show corrections control and follow these steps:

1. Enable the LUT option.

2. Load the LUT correspondent to the screen you will be viewing your renders on.

3. Untick Convert To Log Space... to see a correct preview of the LUT.

4. For V-Ray Next only: make sure Save In Image is disabled. The LUT is only used for preview purposed and should not be not embedded when saving out renders.

Fusion

Setting up Fusion is also quite easy but there are a few things that need to be taken into account especially when migrating from an older workflow.

Unlike V-Ray, Fusion cannot support for both Gamut (sRGB) and Custom LUT previews to be enabled at the same time. As we are working with Linear renders and doing calculations in Linear Space we need to preview the result in Gamma/sRGB Space. Usually, to do this the LUT option in the Image View is enabled and set to Gamut View LUT. This Gamut (sRGB) LUT is actually embedded in our final render output from Fusion as images afterwards are only meant for viewing/printing, thus we need an sRGB output.

So, alternatively, we can use the Gamut node itself, which is at the very end of every Comp, for previewing, by keeping it loaded into the Image View all the time. This means that even though it sits just before the Saver node, we need to add it once we start a new Comp and every next node or operation we need to do or use, be it Color Corrections or Merging Backgrounds, needs to happen before this Gamut node so we can see the result correctly.

By taking this approach we can use the LUT option now set to Fusion View LUT from where we can load our custom monitor calibration based LUT. Find below an illustration of how a normal setup should look:

After we've established how to preview our comp from now on, let's finally setup our custom LUT. Make sure to choose the proper one (Left or Right) based on the monitor that you use for Fusion.

Once an image is loaded into the Image View (through the Gamut node) follow the steps below:

Finally, the Gamut node itself (that we are using for both preview and rendering) should be set to output in sRGB Space like in the image below.

Color Profiling

As mentioned in the beginning of this article, both 3ds Max and Fusion are color agnostic and cannot recognize color profiles. This also means that they cannot embed color profiles - after rendering an image from either of these two programs it doesn't have a color profile.

Be it for print (Adobe 1998) or web (sRGB) we need to embed color profiles into our images so when presented through different mediums their color can be interpreted correctly.

So, the final step in our process is embedding the correct color profile to our images. First we need to setup Photoshop's Color Settings correctly. To do so go to Edit>Color Settings and under Settings choose Europe Prepress 3

After Photoshop is setup like this it will ask, upon opening an image without a profile, what it should do. There are two possible scenarios:

Images for Web

Images meant for the Web need to have an sRGB profile embedded. That's why, when opening images that will be used on the web (be it for final delivery or for upload to client), we need to assign sRGB profile.

Images for Print

Images meant for Print should have Adobe 1998 profile embedded. However, as we are working based on sRGB we need to first assign sRGB profile (as we do with images for web) and only then convert to Adobe 1998. The conversion process, unlike the assigning, tries to keep the appearance of the colors, which is what we want, by changing their RGB values.

Conclusion

This whole process gives us the opportunity to keep product colors consistent and untouched throughout the whole workflow. In a sense we start from Photoshop by either choosing a sRGB color or making a sRGB texture and then keep its properties until the very end where, again in Photoshop, we can get the exact same color.