CompTIA A_ Certification All-In-One Exam Guide, Seventh Edition - Michael Meyers [319]
Figure 19-9 One triad
Dot Pitch
The resolution of a monitor is defined by the maximum amount of detail the monitor can render. The dot pitch of the monitor ultimately limits this resolution. The dot pitch defines the diagonal distance between phosphorous dots of the same color, and is measured in millimeters (mm). Because a lower dot pitch means more dots on the screen, it usually produces a sharper, more defined image (see Figure 19-10). Dot pitch works in tandem with the maximum number of lines the monitor can support to determine the greatest working resolution of the monitor. It might be possible to place an image at 1600 × 1200 on a 15-inch monitor with a dot pitch of 0.31 mm, but it would not be very readable.
The dot pitch can range from as high as 0.39 mm to as low as 0.18 mm. For most Windows-based applications on a 17-inch monitor, many people find that 0.28 mm is the maximum usable dot pitch that still produces a clear picture.
Figure 19-10 Measuring dot pitch
Bandwidth
Bandwidth defines the maximum number of times the electron gun can be turned on and off per second. Bandwidth is measured in megahertz (MHz). In essence, bandwidth tells us how fast the monitor can put an image on the screen. A typical value for a better-quality 17-inch color monitor would be around 150 MHz, which means that the electron beam can be turned on and off 150 million times per second. The value for a monitor’s bandwidth determines the maximum VRR the video card should push the monitor for any given resolution. It reads as follows:
maximum VRR = bandwidth ÷ pixels per page
For example, what is the maximum VRR that a 17-inch monitor with a bandwidth of 100 MHz and a resolution of 1024 × 768 can support? The answer is
maximum VRR = 100,000,000 ÷ (1024 × 768) = 127 Hz
That’s a pretty good monitor, as most video cards do not push beyond 120 Hz! At a resolution of 1200 × 1024, the vertical refresh would be
100,000,000 ÷ (1200 × 1024) = 81 Hz
So, we would make sure to set the video card’s VRR to 80 Hz or less. If you had a monitor with a bandwidth of only 75 MHz, the maximum VRR at a 1200 × 1024 resolution would be only 61 Hz.
Most monitor makers know that people aren’t going to take the time to do these calculations. Instead, they do the calculations for you and create tables of refresh rates at certain resolutions to show what a monitor can do.
Great! Now that you have the basics of CRT monitors, let’s turn to LCD monitors. Although the technology differs dramatically between the monitor types, most of the terms used for CRTs also apply to LCD functions.
LCD Monitors
Liquid crystal displays (LCDs) are the most common type of display technology for PCs. LCD monitors have many advantages over CRTs. They are thinner and lighter, use much less power, are virtually flicker-free, and don’t emit potentially harmful radiation. LCDs still have resolution, refresh rates, and bandwidth, but LCDs also come with their own family of abbreviations, jargon, and terms you need to understand so you can install, maintain, and support LCDs.
How LCDs Work
The secret to understanding LCD panels is to understand the concept of the polarity of light. Anyone who played with a prism in sixth grade or has looked at a rainbow knows that light travels in waves (no quantum mechanics here, please!), and the wavelength of the light determines the color. What you might not appreciate is the fact that light waves emanate from a light source in three dimensions. It’s impossible to draw a clear diagram of three-dimensional waves, so instead, let’s use an analogy. To visualize this, think of light emanating from a flashlight. Now think of the