How to choose a monitor

The most important specifications

• Your computer source. Will you show computer images with your new monitor? If so, what resolution will it need to display? Resolution measures the amount of detail that can be seen in a video or computer image, expressed as the number of lines visible on a test pattern. VGA requires 640 x 480 resolution, S-VGA 800 x 600, XGA 1024 x 768, SXGA 1280 x 1024, UXGA 1600 x 1200 and engineering workstations can run higher. Another way to express these resolutions is in scan rates, and, for those with specialized graphics cards or workstations, we have included those in our comparison charts as well.

• Your video source. Do you need to show S-video or just composite? Will you need to show tapes from overseas in PAL or SECAM format? Will you need to show the new digital HDTV format?
  
  If you do need HDTV, a component input is the preferred connector. Though the new digital systems also have composite inputs, the component connector will reduce noise by minimizing crosstalk within the video signal.

• Video resolution is a key specification that can serve as an overall indication of the picture quality of the monitor. Normally your monitor's resolution will be higher than your source: VHS is about 220-260 lines, VHS-HQ 300, off-air TV signals just over 300, S-VHS 400-440. Strictly speaking, a monitor offering higher resolutions is a waste if you're showing standard video, but most viewers will agree that it looks better, because of a number of factors that don't show up in the specs.
  
  When looking at new digital video formats, resolutions get much higher. There are four DTV bandwidths that will be commonly used. To show 480i images at full resolution, your monitor must be able to show 640 x 480 lines; 480p requires 704 x 480, 720p requires 1280 x720, and 1080i requires 1920 x 1080. In practice, most monitors won't display 1080i or even 720p resolutions, and so they will simply show these signals at the highest resolutions they are capable of.

• Progressive and interlaced scanning are becoming important considerations with DTV formats. Interlaced scanning, used in all analog video monitors, interlaces two pairs of fields, each containing half the scan lines. Progressive scanning, used in most computer monitors and new 480p and 720p DTV formats, scans the entire picture as a single frame. Image quality is significantly better with progressively-scanned pictures.
  
  
• Aspect ratio is also becoming important with digital formats. Standard video has an aspect ratio of 4:3—that is, the ratio 4 to 3. HDTV (1080i and 720p), however, uses a wide screen ratio of 16:9, which is the aspect ratio used for movies. A monitor built to either aspect ratio will show both, but if you want to fill the screen with the best possible image, you need a unit with the ratio that matches what you most often view.
  
  

• Screen size vs. audience size. Rules about monitor sizing seem to be ignored more often than followed, but you need to be aware that, if you stretch these rules, viewability becomes a real issue.
  
  Current thinking is that the maximum viewing distance for video sources should be about eight times the height of the image and for computer about six times. This formula works for both traditional 4:3 aspect ratio monitors and 16:9 wide-screen sets, but if you show a wide screen image on a standard monitor, the top and bottom of the screen will not be used. Thus the image height and viewing distance will be about 25% less. (Showing 4:3 images on a 16:9 monitor does not affect viewing distance.)
  
  The person farthest away in your audience should be no more than:
  
  Standard 4:3 aspect monitors
  

  Diagonal	Full screen 4:3 video	Full screen 4:3 computer	Masked to 16:9 video	Masked to 16:9 computer
  20"	8.0'	6.0'	6.0'	4.5'
  27"	10.8'	8.1'	8.1'	6.1'
  32"	12.8'	9.6'	9.6'	7.2'
  36"	14.4'	10.8'	10.8'	8.1'
  40"	16.0'	12.0'	12.0'	9.0'
  50"	20.0'	15.0'	15.0'	11.3'

  Wide-screen 16:9 monitors
  

  Diagonal	Masked to 4:3 video	Masked to 4:3 computer	Full screen 16:9 video	Full screen 16:9 computer
  30"	9.8'	7.4'	9.8'	7.4'
  37"	12.1'	9.1'	12.1'	9.1'
  42"	13.7'	10.3'	13.7'	10.3'
  50"	16.3'	12.3'	16.3'	12.3'
  56"	18.3'	13.7'	18.3'	13.7'

  
  

• Direct video inputs: The difference between a monitor (or monitor/receiver) and a television is important: the monitor has direct video and audio inputs, the pure receiver only an antenna input. Having a video input means that a videotape or disc image will be much clearer. Using a television, you have to convert the video signal to radio frequency, then convert it back again to video (that's what you're doing when you use the RF output on the VCR and channel 3 or 4 on the receiver). The two extra steps add quite a bit of noise.

• In the same way, S-video inputs are not necessary to show an S-video tape, as all S-VHS and Hi-8 VCRs have S, composite and RF outputs. But a monitor with S inputs will show S-video images at a higher resolution and with much less noise cased by crosstalk between the chroma (color) and luma (detail) signals, because it carries these signals on separate cables.

• Component video inputs separate the signal into three parts, dividing the chroma into red, green and blue components (with luma included with the green). A component signal is as clean as S-video, but offers much more color detail. You'll find component connectors on DTV-ready monitors and projectors, DVD players and digital VCRs.

• The kind and number of computer inputs are also important. Most PCs and Macs require analog RGB inputs; some older and some specialized systems will require TTL inputs.

• Brightness is an important specification, though not generally provided by CRT monitor manufacturers. It is, however available for many plasma units, given in cd/m2, or candellas per square meter.

• Commercial UL approval means that the unit has be rated as safe for use is a school or business. These safety standards are higher than those for a home.
  
  
  

Useful features
Beyond the basics, you'll want to consider whether or not your new monitor includes:

• Multiple inputs and outputs allow you to switch between more than one computer or video source

• Loopthrough means that the unit has video (or computer) and audio outputs as well as inputs allowing you to daisy-chain monitors or use your desktop computer monitor at the same time as your display monitor.

• Auto scanning allows the monitor to sense the incoming computer or video signal and lock onto it without adjustment. All of the monitors United Visual offers have this feature, but many older or lower quality units do not.

• Scan mode memory, available in many computer monitors, stores any adjustments you make for a given input separately from those for a different input.

• A TV tuner allows you to access broadcast or cable programming. A tuner is not a necessity if you're using a VCR (as most VCRs already have tuners).

• A built-in VCR can also be useful, particularly if you have limited space or are planning to transport the unit.

• On-screen menus simplify the accurate setup or adjustment of many monitors.

• Clone programming allows you to set up one unit the way you want it, then copy all settings to additional monitors. It can make a big difference in business networks and video distribution settings, as an initial time saver and a tool to keep image quality high on every monitor.

• Automation features, whether event programming or a simple on/off timer, can be very useful for monitors used in public displays or networks.

• Security features, such as channel lock, a removable mask or more advanced control lock features, are important for pubic displays and classroom networks, where viewers might change settings.

• Production features, such as overscan/underscan, rack mounting, and sync input, are available in monitors from United Visual, though we have not included them in this on-line catalog. Please call for details.

Beyond the specifications
Comparing specifications will take you only so far in choosing a computer or video monitor. You'll need to see the unit demonstrated or talk to your dealer to get a feel for:

• Reliability. How long will a monitor last? Does its manufacturer have a good reputation? What's the warranty?

• Serviceability. How quickly can your monitor be serviced if it fails? Are you purchasing it from an authorized service center? If not, what will you do when it needs repair?

• Flatness and squareness of the picture tube is a consideration for the overall image quality and the impression you'll make on your audience. It is also an indication of the age of the technology going into the monitor's manufacture.

• Audio quality. We have not listed detailed audio specs for the monitors in this catalog, as they are typically not available from monitor manufacturers. But audio can be important, and an audience will perceive an identical image to be of higher quality if the accompanying sound is better