• sRGB vs REC709 – An introduction and FFmpeg implementations

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    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.

    2. Digging Deeper

    FeaturesRGBRec. 709
    White pointD65 (6504 K), same for bothD65 (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 sizeIdentical triangle on CIE 1931 chartIdentical to sRGB
    Gamma / transferPiecewise curve: approximate 2.2 with linear toePure power-law γ≈2.4 (often approximated as 2.2 in practice)
    Matrix coefficientsN/A (pure RGB usage)Y = 0.2126 R + 0.7152 G + 0.0722 B (Rec. 709 matrix)
    Typical bit-depth8-bit/channel (with 16-bit variants)8-bit/channel (10-bit for professional video)
    Usage metadataTagged as “sRGB” in image files (PNG, JPEG, etc.)Tagged as “bt709” in video containers (MP4, MOV)
    Color rangeFull-range RGB (0–255)Studio-range Y′CbCr (Y′ [16–235], Cb/Cr [16–240])


    Why the Small Differences Matter

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  • Aputure AL-F7 – dimmable Led Video Light, CRI95+, 3200-9500K

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    High CRI of ≥95

    256 LEDs with 45° beam angle

    3200 to 9500K variable color temperature

    1 to 100% Stepless Dimming, 1500 Lux Brightness at 3.3′

    LCD Info Screen. Powered by an L-series battery, D-Tap, or USB-C

    Because the light has a variable color range of 3200 to 9500K, when the light is set to 5500K (daylight balanced) both sets of LEDs are on at full, providing the maximum brightness from this fixture when compared to using the light at 3200 or 9500K.

    The LCD screen provides information on the fixture’s output as well as the charge state of the battery. The screen also indicates whether the adjustment knob is controlling brightness or color temperature. To switch from brightness to CCT or CCT to brightness, just apply a short press to the adjustment knob.

    The included cold shoe ball joint adapter enables mounting the light to your camera’s accessory shoe via the 1/4″-20 threaded hole on the fixture. In addition, the bottom of the cold shoe foot features a 3/8″-16 threaded hole, and includes a 3/8″-16 to 1/4″-20 reducing bushing.