How to Use Kdenlive Vectorscope for Color Accuracy

This guide explains how to access, read, and use the vectorscope monitor in Kdenlive to ensure precise color accuracy in your video editing projects. You will learn how to interpret the vectorscope’s graphical display of hue and saturation, monitor color levels, and utilize the skin tone line to achieve professional, balanced color grading.

Step 1: Open the Vectorscope in Kdenlive

To begin analyzing your footage, you need to enable the vectorscope monitor within the Kdenlive interface.

1. Open your Kdenlive project and select the clip you want to analyze on the timeline.
2. Go to the top menu and select View > Scopes > Vectorscope.
3. Alternatively, you can switch to the dedicated Color workspace from the top-right workspace switcher, which automatically displays the vectorscope alongside other color analysis tools.

Step 2: Understand the Vectorscope Display

The vectorscope is a circular graph that measures the color information (chrominance) of your video signal. It does not display brightness (luminance); it only shows hue and saturation.

• Hue (Color): The angle or direction of the pixels plotted on the graph represents their color. Around the circle, you will see targets for primary and secondary colors: Red (R), Magenta (Mg), Blue (B), Cyan (Cy), Green (G), and Yellow (Y).
• Saturation (Intensity): The distance of the pixels from the center of the circle represents their saturation. The center point represents zero saturation (true black, white, or gray). The further the pixels spread toward the outer edges, the more saturated the colors are.
• The Skin Tone Line: A diagonal line extending from the center toward the upper-left quadrant (usually between Red and Yellow). Regardless of race or ethnicity, human skin tones fall along this line.

Step 3: Check for Color Casts (White Balance)

A color cast occurs when neutral colors (like white or gray) are tinted with an unwanted color. You can use the vectorscope to identify and fix this.

1. Find a frame in your video that contains a known neutral reference, such as a white piece of paper, a grey card, or a neutral wall.
2. Look at the vectorscope. If the central cluster of pixels (representing the neutral tones) is pulled away from the center toward a specific color (like blue or orange), your video has a color cast.
3. Apply the Lift/Gamma/Gain or Color Balance effect to your clip.
4. Adjust the controls until the cluster of pixels representing your neutral reference sits directly in the center of the vectorscope.

Step 4: Verify Skin Tone Accuracy

Ensuring natural skin tones is critical for professional-looking video.

1. On your timeline, temporarily apply a Crop or Alpha Shapes effect to isolate a patch of skin on your subject’s face.
2. Look at the vectorscope trace. The pixels representing the skin should align directly on or very close to the skin tone line.
3. If the trace drifts too far toward red (sunburnt look) or yellow (jaundiced look), use the Color Balance or Hue Shift effect to nudge the color of the skin until the trace aligns with the skin tone line.
4. Remove or disable the temporary crop effect once the adjustment is complete.

Step 5: Prevent Oversaturation

Broadcast and online streaming platforms have limits on how much color saturation they can display without artifacting or clipping.

1. Observe the outer boundaries of the vectorscope. The targets (R, G, B, C, M, Y) represent safe color limits.
2. Ensure your color traces do not extend past these targets.
3. If your colors are extending beyond the safe zones, apply the Sat (Saturation) effect and lower the global saturation until the traces sit safely within the boundaries.