A monitor is the display device used to output the video that is processed by a video card. The most common PC monitor technologies are CRT (Cathode Ray Tube) and LCD (Liquid Crystal Display).
LCD panels use a liquid crystal material made of polarized molecules to produce an image. An electric current is passed through the liquid and causes the crystals to align so that light cannot pass through them. There are two types of LCD panels. Active and passive matrix. Active matrix LCD panels offer a faster response time making them appropriate for full motion video, animation, mouse movement and gaming. Active matrix also provides a higher degree of color saturation. Passive matrix is an older form of LCD technology that controlls pixel processing for entire areas of the screen instead of individual pixels like active matrix dislplays. Passive matrix panels have reduced color, lower contrast ratios and higher response times.
Choosing A LCD Monitor
When choosing a LCD monitor, things to consider include response time, pixel pitch, screen size, viewing angle, brightness, contrast ratio, dead pixels, and resolution.
- Panel Type: There are three main panel types: S-IPS, S-PVA/MVA and TN. S-IPS is the hardest to find and most expensive, but in general offers the best image quality of the three. S-IPS are best suited for graphic designers or anyone who deals with photo editing and needs accurate colors. S-PVA/MVA are similar to S-IPS, but their viewing angles aren't quite as good as S-IPS and many suffer from color shifting. However, there are many of these panel produced and they are cheaper than S-IPS panels. They also offer the highest contrast ratios. TN are at the low end of LCD panels. They are very inexpensive and offer excellent response times which makes them great for gaming. The downside is TN panels have the worst color accuracy of the three and very limited viewing angles.
- Response Time: Response time is the amount of time in milliseconds (ms) it takes for a pixel to turn on and off. A high response time can cause motion blur in PC games and full motion video. A response time of 12ms or lower is recommended, however this is subjective and varies from person to person.
- Pixel Pitch: The distance between pixels, usually measured in millimeters. The smaller the pixel pitch, the sharper the image.
- Screen Size: Unlike CRT monitors, which are measured by the diagonal length from the bottom left to the top right of the screen including the case, LCDs are measured by the actual viewable area of the LCD. This means in a comparison with an LCD and CRT monitor of the same screen size, the LCD will always have a lager display.
- Viewing Angle: LCD panels have limited viewing angles. They lose contrast and become hard to read at some angles while having better contrast and are easier to read at others angles.
- Brightness: The measure of how much light an LCD panel can produce is measured in candelas per meter squared (also known as nits). Generally, the higher the nits, the better the image quality will be.
- Contrast Ratio: This is the measure of difference in light intensity between the brightest white and the darkest black. An LCD panel with a high contrast ratio should have better color representation than one with a lower contrast ratio.
- Dead Pixels: A dead pixel (also know as a stuck pixel) is a defective pixel that remains a solid color or stays either unlit or permanently lit. If dead pixels are noticeable on an LCD panel they can become very distracting. Most LCD manufacturers have improved their manufacturing process to minimize or stop dead pixels, though one or two dead pixels are still common on lower quality LCD panels. It is possible on occasion to fix a stuck pixel using the method listed here.
- Resolution: All LCDs have what is know as a native resolution. The native resolution is measured by the number of horizontal and vertical pixels that make up the LCD matrix of the display. Not running in the native resolution will cause the panel to use extrapolation, which attempts to blend multiple pixels together to produce the image as if it were running in the given resolution. This can result in a fuzzy, less detailed image. LCDs should always be ran in their native resolution for optimal image quality.
LCDs have many advantages over CRT monitors. LCDs require less power to operate, are free from flicker, reduce glare and the physical construction of an LCD is much smaller and ligher than a CRT.
Karl Ferdinand Braun is the inventor of CRT technology. Braun built the first CRT oscilloscope in 1897. To this day some still refer to CRTs as the "Braun tube". CRT monitors use filaments located at the back of the CRT which emits a beam of electrons on the screen. The beam of electrons is directed by plates to the top of the screen first, from left to right, and then down to the next line creating the image as the beam moves from top to bottom of the screen.
Choosing A CRT Monitor
When choosing a CRT monitor, things to consider include screen size, refresh rate, dot pitch and maximum resolution.
- Screen Size: The screen size is the measure of the diagonal length of the CRT. Since CRTs are measured diagonally from one corner of the case to the opposite instead of by their viewable area, a CRT will generally have a physically smaller display than that of an LCD with the same rated screen size. Screen size is one of the main variables that affects the price of a CRT monitor.
- Refresh Rate: Refresh rate is the number of times per second the screen is redrawn expressed in hertz. Slow refresh rates will produce a noticable flicker. Higher refresh rates produce a picture with very little or no flicker that is easier on the eyes. A minimum of 75 Hertz is recommended.
- Dot Pitch: Dot pitch is an important factor of the image quality of a monitor. Dot pitch is the measurement of the distance between two phosphor dots of the same color on a monitor. The smaller the dot pitch, the better image quality a monitor will have.
- Resolution: Resolution is the number of pixels displayed on screen. The higher the resolution, the sharper and more detailed the picture will be. CRTs do not have a native resolution like LCDs which means they can use many resolutions without the LCD side effects.
April, 2008 Update: CRT's are all but obsolete with quality ones almost impossible to find, so they really offer no advantage over current LCD displays.
The main advantage of a CRT over LCD panels is price. CRTs are much cheaper than LCD panels. CRTs can operate in multiple screen resolutions without a loss in image quality and CRTs can also display a larger range of colors than LCDs, making them popular in graphics design, gaming and video editing.
When choosing either a LCD or CRT monitor, you should always look at the image quality of the unit before you purchase. Image quality varies greatly in PC monitors and a monitor should be selected with display characteristics that match your personal preferences.