Color Fundamentals
The bedrock principles of video color: the physics of light, human perception, and how standards like the CIE 1931 Chromaticity Diagram provide a universal language for defining and comparing color gamuts.
CIE 1931 Chromaticity Diagram
The CIE 1931 diagram maps all colors visible to the average human. Video color spaces are shown as triangles, defining the gamut (range of colors) they can reproduce. Toggle gamuts to compare key video standards.
Human Perception & Color Models
Human color vision is based on three types of cone cells sensitive to short (Blue), medium (Green), and long (Red) wavelengths of light. This is the principle of trichromacy. Video displays leverage this by using an additive RGB color model.
For efficient video compression, the YCbCr model separates brightness (Luma, Y') from color information (Chroma, Cb/Cr). Our eyes are more sensitive to detail in brightness than color, allowing color information to be compressed with minimal visual impact.
Digital Representation
How the continuous world of color is translated into discrete digital data: bit depth, which determines color precision, and chroma subsampling, a compression technique fundamental to modern video codecs.
Color Depth (Bit Depth)
Bit depth defines the number of shades available for each color channel. Higher bit depth means more colors, smoother gradients, and more flexibility for color grading. 8-bit is standard for SDR, but 10-bit or higher is essential for HDR.
~16.7 Million Colors
256 shades per channel
Chroma Subsampling
Chroma subsampling reduces color data by sampling at a lower resolution than brightness. The notation J:a:b (e.g., 4:2:2) describes this sampling. Select a scheme to see how it works.
In the Camera
Capturing a great image starts in the camera: the exposure triangle of aperture, shutter speed, and ISO, and transfer functions (like Log curves) that maximize dynamic range for post-production.
The Exposure Triangle
Exposure is controlled by three interdependent settings. Changing one requires adjusting others to maintain desired brightness. Each setting also has a critical secondary effect.
Aperture (f-stop)
Controls lens opening size. Wider aperture (e.g., f/1.8) lets in more light and creates shallow depth of field.
Shutter Speed
Controls sensor exposure time per frame. Slower speed (e.g., 1/50s) creates more motion blur, often considered cinematic.
ISO/Gain
Amplifies sensor signal. Higher ISO allows darker shooting but introduces noise and reduces dynamic range.
Transfer Functions (OETF)
An OETF (Opto-Electronic Transfer Function) translates scene light into a video signal. While standard gamma curves (like Rec.709) are for direct viewing, Log curves capture high dynamic range.
Log footage looks flat and desaturated, but it preserves highlight and shadow detail, providing maximum flexibility for color grading.
Post-Production & Display
Bridging capture and viewing: color grading for artistic control, and High Dynamic Range (HDR) technology for brighter highlights, deeper blacks, and wider color gamuts.
Color Grading & LUTs
Color grading alters and enhances video color to set a mood, create a style, or correct issues. This is where "flat" Log footage is transformed into its final look.
Look-Up Tables (LUTs) are key to this process. A Technical LUT converts footage from one color space to another (e.g., camera Log to Rec.709). A Creative LUT applies a specific artistic look or color palette.
High Dynamic Range (HDR)
HDR allows displays to show a much greater range of brightness and color than Standard Dynamic Range (SDR). Key HDR formats include:
- HDR10: An open standard using the PQ transfer function and static metadata. Common baseline for HDR content.
- Dolby Vision: Proprietary format with dynamic metadata for scene-by-scene or frame-by-frame optimization.
- HLG (Hybrid Log-Gamma): Royalty-free standard for broadcast, backward-compatible with SDR displays.
| Feature | Rec. 709 / sRGB | DCI-P3 (Theatrical) | Display P3 | Rec. 2020 |
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