Test Data

If you are looking for some test data, you can download the following bits and bobs:

Introduction and Overview

We’ll be running all stills photography through RawTherepee (5.11+). RawTherepee works well within an ACES pipeline and the latest version does not have any issues with image cropping (as explained below).

We are using RawTherapee to convert the images from RAW to 32bit TIF. Once converted to 32bit TIF in ACEScg, you can take the images into Nuke or PTGui for further grading or processing.

At each stage, the data should be versioned up, allowing you to always go back to the RAW data or compare between graded/ungraded reference. For example:

v001: RAW (cr2, arw, etc) – this is the original captured data. This data should be archived.
v002: 32bit TIF (ACEScg) – this is the RAW data converted in RawTherepee.
v003 (lighting ref): 32bit EXR (ACEScg) – this is the graded data modified and output from Nuke, ready for lighting.
v003 (texture/lookdev ref): 16bit TIF (utility -sRGB – Texture) – this is the graded data modified and output from Nuke, ready for texturing.

It’s true that the 32bit TIF images output from RawTherapee (which is what we are doing) will be HUGE, so if you are finding that is problematic, then you may want to consider other output options (for example, 16bit TIFs). The reason we are going with 32bit TIF is to ensure no data is clamped. Once you’ve processed your 32bit TIFs as required for lighting, texturing, etc. you could delete the files to save disc space. Although should you need to reprocess the reference, you will need to re-generate them from the RAW images.

Lastly, although you can convert images from RAW to TIF without a colour chart present, ideally, you’d have one present when capturing any onset data. This will help you and your team work consistently and with less guesswork. For more info on the colour chart (along with the grey and chrome ball), check out this doc:

The Grey, the Chrome and the Colour Chart

Lighting Stills Prep Workflow

At CAVE, we are rendering in ACEScg, and for all lighting references, we are also prepping them in ACEScg. This includes HDRIs and lightmaps. However , if you are merging and stitching your HDRIs in PTGui, then we find you can work directly in the PTGui with RAW images and export to ACES, as demonstrated here:

Creating a HDRI Light Map in ACES

But… if you do need to go through RawTherapee, the workflow looks something like so:

Texturing/Look Development Stills Prep Workflow

Similar to the lighting workflow, we’ll be processing the data into ACEScg. We’ll be using the utility -sRGB – Texture colour workflow for texturing (primarily for the base colour/diffuse map). This is to allow us is to easily work between Substance 3D Painter, Mari, Photoshop and Nuke.

The workflow looks something like so:

We’ll be exporting linear ACEScg images in 32bit TIF format from RawTherepee. This is to ensure we lose no data when grading the images in Nuke. From Nuke, and after grading, we can then output the images as utility -sRGB – Texture in 16bit or 8bit, so they can be correctly used in 3D applications such as Maya, Substance Painter, Mari, Photoshop (using OCIO).

If you need to view any images on a standard viewer (in sRGB colour space), you can output as Output – sRGB.

When prepping onset texture reference, we are also assuming the data has been shot as both polarised and cross polarised, and for look development reference, the photography should be shot unpolarised.

For more information on unpolarised, polarised and cross polarised photography, please take a look at this doc:

Unpolarised, Polarised and Cross Polarised Photography

01. Issues with Cropping

Before you begin processing any images, double check the image size in your processing app (in our case Raw Therepee) against the metadata of your original raw image. If the numbers do not match up, then you will have issues with distortion and camera/projection line-up later on.

02. Prepping and Exporting your Images from RawTharepee

Please note that I forgot to enable Abstract Profile and set this to Linear g=1 in the video. So do read the notes below.

In RawTherapee, navigate to the directory containing your RAW (in our case, ARW) images and load them into RawTherapee. For this example, we are using the following images:

\cave_dataProcessing_reference_1001\ldv\

This is a subset of images captured by Clear Angle Studios for our courses:

Exposure

Once you’ve loaded your images, select the colour chart, jump to the Exposure tab and set the following:

clip-out-of-gamut colours: Disable
Highlight reconstruction: Luminance Recovery
Tone curve 1: Linear, Standard
Tone curve 2: Linear, Standard

White Balance

This step is not necessary (as we’ll be doing a proper grade in Nuke) but we like to do it as a kind-of pre-grade.

On the Colour tab, go to White Balance and click on the ‘Pick’ button, and then click on a white swatch.

Colour Management

This is where we will define our Working Profile and Output Profile.

Set the Working Profile to ACESp1.
Set the Output Profile to: RTv4_ACES_AP1

Also – make sure to enable Abstract Profile and set this to Linear g=1 (I forgot to do this in the video):

Your images will go darker and this is normal.

Demosaicing

Jump to the Raw tab now and…

Set the Demosaicing Method to: RCD+VNG4
Set the Border to 0

Crop

Switch to the Crop tab and double check that the image width/height is correct. And then disable the Lens Profile. Set it to None.

Copy/Paste your Modifications to all the Images

As we are dealing with a bracketed set of images, we’ll want to apply our tweaks to all the images. To do this, select your image and hit the right-mouse-button. Then go Processing profile operations > Copy.

…Then hit Ctrl+A to select all the images, and go Processing profile operations > Paste.

Export your Images

If all looks good and once you’ve applied all the tweaks to all the images, select them, hit the right-mouse-button and go ‘Put to queue‘:

Jump to the Queue tab and set the following:

File format: TIFF (32-bit float)
Uncompressed TIFF: Enabled
Save processing parameters with image: Enabled

Once all looks good, kick off the processing of the images.

You should now see something like so:

03. Testing and Outputting your Reference from Nuke

If you now launch Nuke, hit the S key to bring up the Settings and go to the Color tab. Then, set the following:

color management: OCIO
OCIO config: aces 1.2+

Then read in your colour chart and reference images, and make sure the Colorspace is set to default (scene_linear)

Grading your Reference

You can now grade your reference using your standard tools, or in our case, we are simply using the ‘grade‘ node. A huge thanks to Brian Chinnery for sharing a couple of workflows.

For workflow 001, Brian primary works with the mid-grey value.

…and for workflow 002, Brian uses a workflow that first establishes the dark tones, then the highlights, and then the mid-grey values:

You’ll be able to find out more about how Brian tackles VFX lighting on our course, Lighting Fundamentals for VFX.

Outputting your Reference

For writing out images for LIGHTING, we are using the following settings for EXRs (16bit/32bit):

colorspace: ACES – ACEScg
File type: EXR
datatype: 16 bit half / 32 bit float (our preference is 32 bit)
compression: none (our preference)

For writing out images for MODELLING, TEXTURING, LOOK DEVELOPMENT or anything else where the images are to be loaded into an application that is ACES compliant, such as Maya, Substance Painter, Mari, Nuke, Houdini, we are using the following settings for TIFs/PNGs/JPGs (16bit/8bit):

colorspace: utility –sRGB – Texture
File type: TIF, PNG or JPG
datatype: 8 bit / 16 bit (our preference is 16 bit)
compression: none (our preference)

For writing out images for GENERAL use to be viewed on a standard scren or for example, using Windows image tools, we are using the following settings for TIFs/PNGs/JPGs (16bit/8bit):

colorspace: Output – sRGB
File type: TIF, PNG or JPG
datatype: 8 bit / 16 bit (our preference is 8 bit)
compression: none (our preference)

04. Dealing with Distortion for Camera Alignment and Projection

If you do not handle distortion correctly, your reference images may not match your cameras and scan data. It will be an issue when projecting reference images via lined-up cameras in your texturing applications. And it will also make it tricky to review models, textures, etc. consistently.

When lined up correctly, the ST Maps can be used to undistort your reference images.

This can then be double checked in your 3d app.

That’s it. Your images should now be good to go and to be used by other departments.

Links

Pushing an Image for Texturing through the VFX Pipeline – In this doc, we cover pushing your processed onset image through the VFX texturing pipeline.
RawTherapee – RawTherapee is a free, cross-platform raw image processing program.
Jedypod blog – Excellent info on working with RawTherapee for VFX.
The Math of Color Grading with Jed Smith – In this video, Jed takes a close look at the simple mathematical functions behind color grading operations in Nuke.
Nukes Grade Node Demystified by Chris Turner – On this page, Chris breaks down each aspect of the Grade node in Nuke.

Asset and Lighting Courses

The workflows presented here will be further explored in the following courses, kicking off in Feb 2025:

Onset Data Acquisition and Creating Look Dev Environment Courses

If you are looking for a more detailed step-by-step breakdown, you can check out our courses on capturing and working with light maps here:

Support CAVE Academy

Here at CAVE Academy the beauty of giving and sharing is very close to our hearts. With that spirit, we gladly provide Masterclasses, Dailies, the Wiki, and many high-quality assets free of charge. To enable the team to create and release more free content, you can support us here: Support CAVE Academy

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Prepping Onset Stills Photography