1. Basic Comparison

• What they are
  • sRGB: A standard “web”/computer-display RGB color space defined by IEC 61966-2-1. It’s used for most monitors, cameras, printers, and the vast majority of images on the Internet.
  • Rec. 709: An HD-video color space defined by ITU-R BT.709. It’s the go-to standard for HDTV broadcasts, Blu-ray discs, and professional video pipelines.
• Why they exist
  • sRGB: Ensures consistent colors across different consumer devices (PCs, phones, webcams).
  • Rec. 709: Ensures consistent colors across video production and playback chains (cameras → editing → broadcast → TV).
• What you’ll see
  • On your desktop or phone, images tagged sRGB will look “right” without extra tweaking.
  • On an HDTV or video-editing timeline, footage tagged Rec. 709 will display accurate contrast and hue on broadcast-grade monitors.
    

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2. Digging Deeper

Feature	sRGB	Rec. 709
White point	D65 (6504 K), same for both	D65 (6504 K)
Primaries (x,y)	R: (0.640, 0.330) G: (0.300, 0.600) B: (0.150, 0.060)	R: (0.640, 0.330) G: (0.300, 0.600) B: (0.150, 0.060)
Gamut size	Identical triangle on CIE 1931 chart	Identical to sRGB
Gamma / transfer	Piecewise curve: approximate 2.2 with linear toe	Pure power-law γ≈2.4 (often approximated as 2.2 in practice)
Matrix coefficients	N/A (pure RGB usage)	Y = 0.2126 R + 0.7152 G + 0.0722 B (Rec. 709 matrix)
Typical bit-depth	8-bit/channel (with 16-bit variants)	8-bit/channel (10-bit for professional video)
Usage metadata	Tagged as “sRGB” in image files (PNG, JPEG, etc.)	Tagged as “bt709” in video containers (MP4, MOV)
Color range	Full-range RGB (0–255)	Studio-range Y′CbCr (Y′ [16–235], Cb/Cr [16–240])

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Why the Small Differences Matter

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