Calibration Pattern (SMPTE bars)

What the bars are

Color bars are a broadcast test pattern. The seven bars run from brightest to darkest: white, yellow, cyan, green, magenta, red, blue. Each is at 75% level, which here means 191 of 255 in every channel that is switched on, so yellow is red and green at 191 with blue off. The order is not decorative: each step removes one primary, so a missing or swapped channel breaks the sequence in an obvious way.

1. 1

   Open the bars full screen and look straight on.

2. 2

   Check the order and the colors. Yellow should be clearly yellow, cyan clearly cyan, and each bar darker than the one before it.

3. 3

   Look along the edges between bars. Fringes, ringing or smearing point to sharpening or a scaled signal rather than a color problem.

4. 4

   Use it to compare two screens, or the same screen before and after changing picture settings.

Why 75% and not full brightness

Broadcast bars use 75% rather than 100% because full-strength colors could exceed the signal limits of older broadcast equipment. The level also leaves headroom, so a display pushing colors too hard shows it: at 75% the bars should still look clearly separated, not merged into flat, glowing blocks. If your screen shows the bars as uniformly bright, a vivid or dynamic picture mode is probably on.

What this pattern does not include

A full broadcast pattern also has a bottom section with narrow blocks and near-black steps used for setting black level. Those parts only mean something with sourced, standard values for the way a computer sends color, so they are left out rather than guessed. For near-black and near-white steps, use the Screen Contrast Test; for standard color patches with their values, the Color Accuracy Test.