|Mr. Fixit's PC Upgrade and Repair
A PC monitor is based on two technologies known as Cathode-Ray Tube (CRT) and Liquid Crystal Display (LCD). The monitor can be
either a CRT, LCD, Widescreen LCD TV, a Plasma Display, or a Projector. Many of today's monitors use LCD technology that does have
benefits over the CRT monitors. I will show advantages and disadvantages for each technology plus details to help you choose your next
Cathode-Ray Tube (CRT)
CRT monitors do have an advantage over LCDs. CRTs have wider viewing angles (as wide as 170° horizontal and 120° vertical) which
makes them great for presentations. They cost less than a LCD monitor, but cost more to ship due to weight and size of the monitor.
CRTs have a wider resolution range, however, you may need to fine-tune each resolution and refresh rate using the monitors On-Screen
Diagnostics (OSD) controls. The memory in the monitor will store the settings, so the next time you turn on the monitor, the settings will
be applied. CRT monitors provide fast response times while playing full motion video.
Many CRT monitors use a default refresh rate of 60Hz which can strain the eyes after long period of usage due to the flicker. The
graphics card can adjust the refresh rate through Windows display properties and list the monitor's ability at different resolution
limitations. Using a refresh rate of 75Hz will usually work for most resolutions. Refresh rate is the number of times the screen is refreshed
per second. The refresh rate of the graphics card must match that of the CRT to avoid damage to the monitor.
Flat CRTs have less distortion, less glare, and provide higher quality more accurate images than the conventional CRTs. For most cases
a 17-inch monitor is the best bargain.
Liquid Crystal Display (LCD)
LCD monitors have benefits over the CRT counterpart. A 17-inch LCD monitor has the same viewing area as a 19-inch CRT display.
LCDs use direct addressing for each pixel in the display, producing a High-Precision image. LCDs are immune to the common problems
with CRTs like pincushions, barrel distortions, convergence errors, etc. LCDs also use less energy compared to CRTs and do not emit
Very Low Frequency (VLF) and Extremely Low Frequency (ELF) electromagnetic radiation. LCD monitors are compact, light weight, and
can be placed in tight or cramp areas. LCDs can use digital or analog signaling. LCDs provide a comparable Mean Time Before Failure
(MTBF) than CRTs. In LCDs, the primary failure is the backlight, which is cheaper to replace than a CRT.
LCD monitors are becoming popular as the prices begin to decline and are available in 2 forms: 4:3 (Full Screen) and 16:9 (Wide
Screen). Full Screen monitors use the same standards as a TV and are called 4:3 ratio monitors, but are sometimes referred as 1.33:1
ratio monitors. These types of monitors can reach resolutions as high as 1600 X 1200 on a 20.1-inch flat screen. Wide Screen LCD
monitors have other benefits. With wide screen LCDs you can watch wide screen movies and TV shows with out seeing the 'letter box' as
you do on 4:3 displays. Most support multiple connection types to allow a connection to any computer. Some even support portrait mode
to ease document editing. They are great for photo and video editing with all that extra desktop space. Wide screen monitor resolutions
can reach up to 1920 X 1200. Be aware of the differences between computer LCDs and TV LCDs. Computer LCDs will provide higher
resolutions and sharpness than TV LCDs and are recommended for detail work where as TV LCDs are good for TV, DVD, Game
All monitors have one or more video connectors. The monitor must support the graphics card's video connection interface. The most
common is the Video Graphics Array (VGA).
The VGA transmits analog composite video as separate Red, Green, and Blue video signals. This connector also transmits
the Horizontal and Vertical Sync signals from the graphics card to the monitor. Monitors with both VGA and Digital
connectors have built-in Analog to Digital Converters (ADC).
The Digital Flat Panel (DFP) connector was used on earlier LCD monitors to avoid converting analog signals to
digital. It transmits both analog and digital to provide backward capability for legacy VGA connectors. The DFP has
since been replaced by the DVI.
The Digital Visual Interface (DVI) became standard on many LCDs, replacing the VGA and DFP. Many Digital TVs,
use the DVI-D connector to use High-bandwidth Digital Content Protection (HDCP) and others use DVI-I (shown Left)
because it provides analog signals to convert the DVI into a VGA connector.
High-Definition Multimedia Interface (HDMI) is more advanced than DVI. It can transmit both Audio and Video signals
in a single connector. HDMI is compatible with DVI-I and DVI-D adapters that can be used to convert HDMI to DVI or
vise-versa, however, some DVI adapters are not compatible with HDCP.
Digital projectors were often used in board rooms and training facilities, but have been making its way into Home Theater systems.
There are two versions: LCD and DLP. LCD projectors separates white light into Red, Green, and Blue wavelengths then directs them
through the corresponding LCD panel. Each LCD pixel is either open to pass light or closed to block light. Then the RGB signal is
combined and projected onto the screen or surface.
Digital Light Processing (DLP) projectors use a spinning color wheel and a Digital Micro-mirror Device (DMD) to project an image. As the
color wheel spins to change RGB colors, each DMD mirror will either reflect light through the lens for projection or reflect the light away
from the lens. Each mirror acts as a pixel and is controlled by a processor.
These are commonly used in TVs from 30" and larger. They contain millions of small cells (pixels) with electrically charged ionized gas
that illuminates the RGB phosphors triads to collectively form an image. Plasma displays are best suited for TVs, however, some do
provide a VGA or DVI port for PCs.
Plasma displays provide superior contrast ratios with deeper black levels, Wider viewing angles than LCDs, and produce less
motion-blurs from fast moving frames. However, Plasma Displays are susceptible to screen burn-in and image retention, newer models
use orbiting pixels to reduce the effect by moving the entire image slower than the human-eye can see. Flickering or Shimmering may be
noticed with different hues, intensities, and other dither patterns. Some models may experience a lost in luminosity over time. The
screen-door effect may be seen in 50" and larger TVs at close range. They use more energy than LCD TVs. They do not work well in
altitudes over 6,500 feet and may cause a "buzzing" noise (manufactures rate them by altitude). Plasma Display's Radio Frequency
Interference (RFI) interferes with AM, HAM, and Shortwave radios.
Monitor Shopping Guide
Before you buy a new monitor, here are some things to consider.
Luminance is measured in candelas per square meter (cd/m2), also known as a Nit. This indicates the brightness of the display. Higher
luminance means a brighter picture.
Aspect Ratio is the ratio of the horizontal length to the vertical length. Full-Screen (standard) displays have an aspect ratio of 4:3 (a.k.a.
1.33:1), whereas Widescreen displays have a ratio of 16:9 ( a.k.a 1.77:1, 1.85:1 or 2.40:1).
Viewable image size is measured diagonally, but the actual widths and heights are more informative since they are not affected by the
aspect ratio in the same way. The viewing area size on a 15" LCD is equivalent to a 19" CRT.
Screen Resolution is the number of distinct pixels (dots) in each dimension that can be displayed. This is displayed as Width x Height.
For example a monitor with 1440 x 900 resolution means there are 1,440 pixels in width by 900 pixels in height. When you multiply W x H,
you get a total of 1,296,000 pixels. The maximum screen resolution is known as the monitor's Native Resolution and is limited to it's Dot
Dot Pitch (a.k.a Pixel Pitch) is the distance, in millimeters (mm), between the center of one triad (group of red, green, blue dots) color dot
to the center of an adjacent triad of the same color dot. High quality monitors can have a dot-pitch of 0.26mm or smaller. A smaller dot-
pitch will produce a sharper image. Dot Pitch mostly applies to CRT monitors.
Refresh Rate is the frequency at which the display is illuminated per second. Most monitors default to 60Hz, but can often be changed to
a higher refresh rate such as 75HZ to as high as 120Hz. Higher refresh rates reduce strain on the eyes, but the maximum refresh rate is
limited to the display's response times.
Response time is the time, in milliseconds, a pixel takes to go from active (white,) to inactive (black), and back to active (white) again.
Lower numbers mean faster transitions and therefore fewer visible image artifacts. Monitors with a response time of 16ms or less are
great for movies, 3D video games, animation, etc.
Contrast ratio (a.k.a. Static Contrast Ratio) is the ratio of the luminosity of the brightest color (white) to that of the darkest color (black)
that the monitor is capable of producing. A good monitor will have a contrast ratio of 250:1, meaning the brightest color is 250 times
brighter than the darkest color. Newer displays may use Dynamic Contrast Ratio (DCR) which controls the brightness of the backlight or
luminance. For example, if the display shows a "dark scary night" scene, the display will reduce the luminance so the scene appears
darker. Displays with a ratio over 1000:1 may be using DCR and are suitable for game consoles and watching movies.
Power Consumption measures the amount of power (Watts) the display will consume per hour.
Delta-E (a.k.a ΔEab, ΔE, or dE) measures the color accuracy (or color differences) of the displayed image. A delta-E below 1 is
imperceptible to the human eye. Delta-Es of 2 to 4 are considered good and require a sensitive eye to spot the difference.
Viewing angle is the maximum angle at which images on the monitor can be viewed, without excessive degradation to the image. It is
measured in degrees horizontally and vertically.
The prices have gone down dramatically over the past decade. CRT monitors are fading as they are being replaced with better technology. PC monitors
costs between $40 and $1,000 depending on your preference. Do your research before buying a monitor.