Common Questions & Other Considerations

Analog and Digital Media

"Analog" refers to a system of recording video images that employs continuously varying waveforms to encode brightness, color and the timing information necessary to reproduce a moving image. Examples of analog video formats are VHS, Betacam SP, and 1/2" reel-to-reel tape (obsolete). Digital media formats include DVD, Digital Beta, DVCAM, and MiniDV. With the exception of DVD, these formats are similar to analog video in that they consist of physical magnetic tape reels stored inside protective cassettes. The critical distinction is the way in which the information is stored. (Digital data is stored as a series of 1's and 0's, while analog data uses a range of numbers such as 0 to 10,000.) When examined closely, analog video appears as a series of lines, while digital video is comprised of pixels, or tiny boxes of color. The difference between analog and digital formats, though subtle, is perceptible.

International Standards: NTSC and PAL

NTSC and PAL are the two main video broadcast standards or systems; they are incompatible with one another. Developed in 1953 in the U.S., NTSC (the acronym for National Television System Committee) is the video standard used in North America and Japan. NTSC videocassettes and DVDs are only playable on equipment that supports this standard. NTSC displays 525 lines of information at 60 half-frames (interlaced) per second. PAL stands for Phase Alternating Line and is the dominant television standard in most of the world, including Europe. PAL delivers 625 lines of information at 50 half-frames per second. PAL videocassettes and DVDs are playable only on PAL equipment. (A third, much less common format is SECAM [Séquentiel Couleur Avec Mémoire], which was engineered in France.) Multi-standard playback devices can read all international formats.

Addressing the Ambient Environment

The environment will significantly impact the exhibition of media installations. Unless properly planned for, ambient light and sound can dramatically impair the presentation of these works. Please visit the Planning Process and Best Practices sections of the Resource Guide for detailed recommendations.

Inadequate Ventilation of Projectors and DVD Players

Projectors and amplifiers that overheat will shut themselves off. Improperly ventilated DVD players will cause DVDs to warp as they heat up, which can cause skipping and other malfunctions. Commonly an overheated DVD exhibits problems as the day progresses and the DVD player heats up. If skipping is caused by heat buildup, cleaning the disc will not help and in fact may damage the DVD. Only ventilating the DVD player will prevent such difficulties.

Ground Hum

Ground hum is an audible hum or light rolling bars in the video image. When possible make sure all equipment is plugged into the same electrical circuit, or at least the same electrical "leg."

Leaving Projectors on Continuously

Leaving a projector on continuously can significantly reduce the projector bulb's rated lifetime.

Color Bars

Color bars are inserted at the beginning of a video program to allow for the proper tuning of a television's or projector's brightness, contrast, and color settings.

Test Tones

Test tones are usually included with color bars and consist of a simple tone for testing speaker response and adjusting audio levels. A complete set of test tones (ranging from 20Hz to 20kHz, the average limits of human hearing) can be used for more specialized testing and tweaking of an audio system.

Other Electrical Considerations

Electrical considerations for exhibitions concern the placement of playback devices, amplification, speakers, and power and A/V cables. Power outlets should be checked to verify they can handle the needed output (when using projectors, amplifiers, etc. it is easy to blow fuses) and to ensure that the power output is clean and consistent. It is best to keep all power and A/V cables away from visitor traffic, but if cable must be run through exhibition space, the entire length must be carefully taped (use duct tape) to prevent accidents.


Even in exhibition environments with gallery attendants, it is important to secure your equipment for safety (if hanging overhead) and theft prevention. A good practice with video projectors is to use a lock or aircraft cable attached to the projector and a secure object.