INTERACTION DESIGN PRINCIPLES FOR INTERACTIVE ...

4.2.4 Line Width
The image on a television screen is composed of interlaced odd and even
scanlines. The NTSC’s 525 line, 30 frames per second system is used in the United
States. NTSC interlaced video draws alternating top and bottom lines for each frame of
video. To reduce interlace flicker, designs for TV-safe graphics should be no less than 2
or 3 pixels wide (“Television Guidelines,” 2004). Also, it is best to avoid detail, since
images with fine details will blur and television viewers won’t be able to see them
properly.
4.2.5 Color
In general, television screens have a more limited overall gamut and a much
higher gamma value than computer monitors, resulting in displays that are higher in both
contrast and saturation. When designing applications on a computer to be displayed on a
television screen, the BBC recommends that images be toned down and desaturated.
Large, clearly defined regions of cool, desaturated colors work best for television (2002).
To avoid color-associated distortion effects such as blooming, tearing, chroma-
crawl, bleeding, interlace flicker, smearing of colors, and moiré patterns, NTSC graphics
must not be too bright, too dark, or too saturated; the maximum saturation brightness in
the color palette should be 85% (“Television Guidelines,” 2004).
NTSC video supports a luma range of 16 to 235. Bright, saturated reds and
yellows will bleed on NTSC monitors, and sharp color transitions will create unwanted
artifacts at the boundaries where they meet. One way to avoid most potential problems is
to keep all RGB values between 16 and 235. Additionally, some graphics programs such
as Adobe Photoshop contain NTSC safe settings (Buehler, 2003)
90