Waveform Monitor

A waveform monitor (often just called « the waveform » or « the scope ») is an instrument that displays the luminance and chrominance values of a video signal in real time. Unlike your eyes — which adapt to brightness and color within seconds and cannot be trusted for absolute measurements — the waveform provides an objective, calibrated readout of every pixel's value. There are three main scope types used in color grading. The luminance waveform (Y waveform) displays the brightness of each pixel across the horizontal axis of the image, with IRE values on the vertical axis from 0 (black) to 100 (white) for SDR, or 0 to 10,000 nits for HDR. Every pixel in the frame is plotted at its corresponding brightness level. A face that reads at 55 IRE is at a known, reproducible brightness — regardless of what the surrounding image looks like or how your monitor is calibrated. The RGB parade splits the signal into red, green, and blue channels and displays each as its own waveform side by side. This is the primary tool for evaluating color balance: if the three waveforms are not aligned in the shadows, midtones, and highlights, the image has a color cast. A blue spike in the shadows means the blacks are tinted blue; a red deficiency in the highlights means whites are cool. The vectorscope displays chrominance (hue and saturation) on a circular graph. The center represents zero saturation (grayscale), and distance from the center indicates saturation level. The angle indicates hue, with six target boxes marked at the positions of primary and secondary colors: R (red), G (green), B (blue), YL (yellow), CY (cyan), MG (magenta). Skin tones should fall along the I-line (the line between red and yellow on the vectorscope, at approximately 123 degrees). If skin tones drift away from the I-line, they look wrong — too orange, too red, or too green — even if you cannot articulate exactly why. The vectorscope with 2x magnification is the standard for skin tone evaluation. Why you grade by scopes and not by eye: your visual system is continuously adapting. After 30 seconds of looking at a warm-toned image, your brain white-balances it and a neutral image suddenly looks too blue. After staring at a bright scene, a normal-exposure scene looks too dark. The scopes do not adapt — they show you the absolute, calibrated truth about your image values. Every professional colorist sets black points, white points, and skin tone values on the scopes first, then adjusts visually for creative intent, then verifies again on scopes.

The first step in any grade is setting the black and white points — and this must be done on the waveform, not by eye. For Rec.709 SDR (per ITU-R BT.709): black should be set to 0 IRE (code value 64 in 10-bit, 16 in 8-bit) and white to 100 IRE (code value 940 in 10-bit, 235 in 8-bit). Values below 0 and above 100 are called super-blacks and super-whites — they exist in the signal but may be clipped by broadcast monitors and streaming platforms. Legal broadcast range requires all values between 0-100 IRE; anything outside may fail QC. To set black point: look at the luminance waveform and find the darkest area of the image that should be true black. Adjust the lift (or offset, or shadows) control until the bottom of the waveform just touches 0 IRE. Do not crush below 0 — you lose shadow detail that cannot be recovered. To set white point: find the brightest area that should be pure white (a practical light, a specular highlight, a white shirt in direct sun) and adjust the gain (or highlights) until the top of the waveform reaches 100 IRE. If the image has no true whites, do not force it — a naturally dim interior scene may legitimately peak at 80 IRE. The RGB parade is the fastest way to diagnose color balance problems. If all three channels rise and fall together — red, green, and blue waveforms align at shadows, midtones, and highlights — the image is neutrally balanced. If one channel is higher than the others in a specific range, there is a color cast in that tonal range. For example, if the blue parade sits 5 IRE higher than red and green in the shadows, the image has a blue cast in the blacks. Correct this by reducing blue lift or adding warmth in the shadows until the three parade channels align. This is faster and more accurate than trying to evaluate color cast visually — especially on an uncalibrated monitor. In DaVinci Resolve, the scopes are always available in the top-right corner of the Color page. You can switch between Waveform, Parade, Vectorscope, Histogram, and CIE Chromaticity. For a standard SDR grading session, keep the Parade scope open continuously — it gives you both luminance and color balance information simultaneously. Switch to the Vectorscope when evaluating skin tones and saturated colors. The Histogram is useful for evaluating overall exposure distribution but less precise than the waveform for setting specific IRE targets.