AfterEffects

Broadcast-safe colors

Analog video signal amplitude is expressed in IRE units (or volts in PAL video). Values between 7.5 and 100 IRE units are considered broadcast-safe; colors in this range do not cause undesired artifacts such as audio noise and color smearing. (In practice, some spikes over 100 IRE are legal, but for simplicity 100 IRE is considered legal here.) This range is equivalent to a range from black to white of 64-940 in 10-bpc values for Y' in Y'CbCr, which corresponds to 16-235 in 8-bpc values. Therefore, many common video devices and software systems interpret 16 as black and 235 as white, instead of 0 and 255. These numbers don’t directly correspond to RGB values.

If you notice that colors of imported footage look wrong—blacks don’t look black enough, and whites don’t look white enough—make sure that you’ve assigned the correct input color profile. The common video color profiles included with After Effects include variants that account for these limited ranges, such as the HDTV (Rec. 709) 16-235 color profile, which interprets 16 as black and 235 as white.

Note: Some video cards and encoders assume that output is in the range 0-255, so limiting colors in your composition and rendered movie may be redundant and lead to an undesired compression of the color range. If colors of your output movie look dull, try assigning an output color profile that uses the full range of colors.

You can use the Broadcast Colors effect to reduce luminance or saturation to a safe level, but the best way to limit output colors to the broadcast-safe range is to create your composition to not use colors out of this range. Keep the following guidelines in mind:

  • Avoid pure black and pure white values.

  • Avoid using highly saturated colors.

  • Render a test movie and play it on a video monitor to ensure that colors are represented accurately.

The Color Finesse plug-in included with After Effects includes excellent tools that can help you keep your colors within the broadcast-safe range. For more information, see the Color Finesse documentation in the following folder: Adobe After Effects CS3/Additional Documentation/Color Finesse 2.

Note: After Effects 7.0 had an Expand ITU-R 601 Luma Levels option in the Interpret Footage dialog box. When opened in After Effects CS3 or later, footage items in projects created with this option will have a corresponding assigned profile.