Standard Definition Broadcast-Safe Concerns

Have you ever watched a low-budget commercial on late-night TV? Listen closely, as you may actually hear the graphics. If whites are too hot, the video track bleeds over into the audio track of a broadcast signal. This can also cause problems when tapes are duplicated. It is an accepted industry practice to keep video signals broadcast-safe.

Recently, creating broadcast-safe graphics has gotten trickier. Many video editing tools have begun to automatically adjust graphics to make them broadcast-safe during import. The system will automatically remap the white and black points to a broadcast-safe value. For example, both Premiere Pro and Final Cut Pro will properly interpret a zero black as 7.5 IRE on a Waveform monitor. Avid systems continue to offer you a choice and will ask if the graphics have RGB levels (0-255) or 601 Levels (16-235).

While this can take care of graphics where luminance is the only concern, it generally does not solve the problem of too much saturation. Whenever you adjust an image, you have to be concerned about modifying its colors to the point where they are no longer "broadcast-safe."

It is important to read the documentation that comes with your video software (or see the guides that come in the Appendixes of this book). If you do need to remap your graphics, then it is better to make this adjustment in Photoshop.

If you need to clamp your graphic to 601 levels, then you'll want to pull things into the 16-235 broadcast-safe range. In doing so, however, you don't want to overdo it, so you must monitor the adjustment. By placing targets using the Color Sampler tool (stored in the same well as the Eyedropper and Measure tools), you can monitor the values of white and black.

In the example (Ch09_BSC.tif), I have placed targets on the clouds (for white) and the deepest shadows (for black). In the Info palette, it is clear that these colors are out of the safe range. Add a Levels adjustment layer and set the output levels to 16 and 235. The colors are now in the safe range. You can leave the adjustment layer floating and modify it at any time within Photoshop.

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