VectorscopeCC: Color Grading in Latent Space

Color grading involves the adjustment of colors in an image to achieve a desired look or feel. It enhances the mood, tone, and overall aesthetic of images or videos. It is used in post-production on a final image, but what happens if we use the concept in stable diffusion?

Installation

You can install VectorscopeCC as an extension for A1111 in Extensions tab (go to Extensions/Available/Load from, and find it in the list). The github repository is this link. After installation, restart A1111 web UI.

Saving VectorscopeCC Parameters to File Metadata

In Settings/User Interface/Infotext check "Add Vectorscope CC parameters to generation information" and Apply settings. This way the settings can be loaded via "PNG Info" or drag and drop image file into a prompt.

Color Grading in Stable Diffusion

Color grading helps establish visual cohesion within a series of images. In stable diffusion, it will also change the scene slightly to fit the parameters. 

How the Parameters Change the Output

The parameters are in ranges with logical effects, but the output variations depend on the model and the scene. In the first example, I am using a prepared style to add warmer colors to the scene.

These examples show extreme ranges of parameters:

Styles

Experiment with various styles. Here (github link) is a list of experimental styles to choose from.

Advanced Noise Settings

You need to experiment with these. Creator of the extension says: "In my experience, 1 - Sin works better for the default Tensor while 1 - Cos works better for the Alt. Tensor". I would add: test various options and fine tune it to your scene, sampler, and model.

Noise Settings Methods

Noise Scaling

In this example PX-Bluetone-CC Style with "Alt." was applied as base modification. The style shifts colors to blue. In combination of Sin Scaling and Cross Method it creates almost a RAW flat color dynamics in the face.

High Dynamic Range HDR Approximation

VectorscopeCC comes with handy script for bracketing and HDR merge for 16-bit HDR approximation. You may read about the technique in this article about HDR for SDXL. 

Conclusion and Tips

VectorscopeCC is an interesting tool to use. You may complement its effects with LoRAs or prompt engineering tricks. Preferably use Hires workflows to completely avoid artifacts in lower resolutions.

You may use VectorscopeCC to lower the contrast in the image, if you intend to use some traditional color grading techniques later. In my experience it is the better solution than to use a lower contrast VAE.