What is Mid-Grey? And the importance of 18% Midtone Grey in Color Grading.

(for the purpose of this post we are working on DaVinci Resolve, the concepts remains same across all softwares but available tools to achieve the same results will vary from platform to platform.)

Understanding 18% Mid-Gray in DaVinci Wide Gamut Color Space

Color grading in digital cinema often involves precise control over exposure, contrast, and color manipulation. One crucial tool in this process is the concept of 18% mid-gray, especially within the context of DaVinci Wide Gamut Color Space. This post will break down the significance of mid-gray, its role in the DaVinci Wide Gamut, and how colorists can utilize it effectively in their grading workflow using DaVinci Resolve.

What is DaVinci Wide Gamut Color Space?

DaVinci Wide Gamut (DWG) is a vast color space developed by Blackmagic Design, designed specifically for high-dynamic-range (HDR) projects. The DaVinci Wide Gamut color space is engineered to cover nearly all colors perceivable by modern capture devices and cameras. It’s invaluable for projects that demand extensive manipulation of colors and luminance without compromising the quality of the image. DWG is designed to cater to the current cinematic requirements, where high color fidelity is essential for HDR content and precise tonal adjustments.

Mid-Gray in Color Grading: An Overview

In the world of color grading, 18% mid-gray acts as a crucial reference point. It represents an 18% reflectance, which serves as a neutral midpoint in exposure. This midpoint is essential because it provides colorists with a consistent, reliable reference that can be used across different scenes and lighting conditions. Using mid-gray as a baseline for exposure adjustments allows for balanced image contrast, giving colorists a starting point to modify highlights and shadows uniformly.

The 18% mid-gray value is also mapped to a normalized level in the DaVinci Intermediate transfer function. Specifically, it is assigned a value of 0.336043 in this color space, which allows colorists to establish accurate pivot points for adjusting contrast. By setting this baseline, both the shadows and highlights are modified evenly, resulting in a balanced and pleasing image that maintains the original artistic intent.

Why 18% Gray?

The choice of 18% reflectance is rooted in traditional photography and cinematography. Studies have shown that the human eye perceives a surface with 18% reflectance as a neutral, balanced gray under standard lighting conditions. This value provides a natural baseline for exposure because it is neither too bright nor too dark. In digital color grading, using an 18% mid-gray reference ensures that the resulting image will not skew toward overexposure or underexposure, making it an optimal reference for setting up scenes.

Setting Up Mid-Gray in DaVinci Resolve

To apply 18% mid-gray in DaVinci Wide Gamut, colorists can follow specific steps in DaVinci Resolve. Here’s a simple guide to get started:

1. Create a New Project:

• Open DaVinci Resolve and either create a new project or open an existing one.

2. Set Up Color Management:

• Go to Project Settings by selecting the gear icon at the bottom right.

• Navigate to the Color Management section.

• Set Color Science to DaVinci YRGB Color Managed.

• Choose DaVinci Wide Gamut Intermediate as the Color Processing Mode.

• Set the Output Color Space to Rec.709 Gamma 2.4 or another preferred output option.

3. Add a Color Generator:

• In the Color workspace, create a new node by right-clicking in the node editor and selecting Add Node > Add Serial.

• Open the Effects Library and select Generators.

• Drag a Color Generator onto your node.

4. Set RGB Values for 18% Gray:

• Adjust the RGB values to 0.18 for each channel, representing 18% gray.

5. Verify with Scopes:

• Use the waveform or vectorscope to confirm the mid-gray value aligns with the expected 0.336 normalized value for mid-gray.

This setup allows colorists to align their exposure and contrast adjustments with the 18% mid-gray reference, ensuring that changes to image dynamics are both precise and balanced across scenes.

Technical Specifications in DaVinci Intermediate

In DaVinci Intermediate’s transfer function, the mid-gray reference point of 0.336043 is essential for maintaining color consistency. The DWG color space offers over 9 stops of dynamic range above this reference, ensuring flexibility in contrast adjustments. This extensive range enables colorists to make subtle modifications without compromising the image quality, which is especially important for HDR content.

The Role of 18% Mid-Gray in Creative Storytelling

The 18% mid-gray reference is not just a technical marker; it serves as a foundational point for creative storytelling in color grading. By adjusting exposure and contrast with this reference in mind, colorists can shape the mood and atmosphere of a scene to convey emotion. For instance, raising the exposure above mid-gray can evoke a light, airy feel, while lowering it can create a somber, intense ambiance.

The colorist’s task is to balance technical precision with artistic vision. By using 18% mid-gray as a baseline, they can confidently explore creative adjustments while maintaining a consistent look across scenes, ultimately enhancing the storytelling impact.

Practical Application of Mid-Gray

In practice, colorists frequently adjust their grading tools based on the mid-gray reference. For instance, when setting the pivot point in contrast adjustments to 0.336, they can streamline the grading process by avoiding the need for excessive modifications in different tonal areas. This enables a more cohesive adjustment across highlights, mid-tones, and shadows, resulting in a refined and polished final product.

The ability to recognize changes above and below the mid-gray value is also critical. This allows for more targeted adjustments that enhance image depth and dynamic range. By anchoring contrast adjustments to mid-gray, colorists can ensure their edits are both efficient and effective.

Conclusion: 18% Mid-Gray as a Cornerstone in DaVinci Wide Gamut

Understanding and implementing 18% mid-gray in DaVinci Wide Gamut empowers colorists to maintain control over exposure and contrast adjustments. The mid-gray reference provides a reliable foundation for making balanced changes that enhance image quality and support the narrative.

By anchoring their work in this reference point, colorists can achieve consistency across scenes while preserving their creative intent. Whether the goal is to create a dramatic contrast or a subtle atmospheric effect, mid-gray in DaVinci Wide Gamut is a vital tool for modern color grading workflows. Through this technical and creative mastery, colorists can deliver visually compelling stories that resonate with audiences.

18% Mid-Gray Cheatsheet by Cullen Kelly

The Mid-Grey Cheatsheet by Cullen Kelly provides standardized values for 18% mid-gray across various log encoding formats, helping colorists position mid-gray accurately when applying LUTs, transforms, or grading. This chart includes values in normalized (0-1), 10-bit, and 12-bit formats for different log curves such as ACEScc, Arri LogC, Blackmagic Film Gen 5, Canon Log 3, DaVinci Intermediate, Fuji F-Log, and S-Log3.

For instance, in DaVinci Intermediate, mid-gray is represented by the normalized value of 0.336, 344 in 10-bit, and 1376 in 12-bit. Each value on the list allows colorists to set consistent exposure baselines across projects using different log curves, ensuring continuity and color accuracy in color grading workflows .

Here is the cheatsheet by Cullen & his video for better understanding.

Mid-Grey Cheatsheet - Cullen Kelly Color.pdf

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