Everything You Need To Know About LCD Monitors

Main Specifications

On this page we will explain the main features found on LCD video monitors and how to interpret them:

• Response time (a.k.a. performance): this feature measures the time the panel delays between switching a pixel from off (black) to on (white). This time is measured in milliseconds and the lower, the better. On a video monitor with a high response time you will see the screen blurred on fast animations (such as games) and fast movements on video playback. Today is easy to find video monitors on the 5 ms range and below, and you should buy a monitor with at least 5 ms response time. If you are into gaming, a 2 ms monitor is recommended.
• Brightness: This spec indicates how well you will be able to see images on your screen on a bright environment. This spec is measured in a unit called candela per square meter (cd/m2) and the higher, the better. For a typical office use, a video monitor with a 300 cd/m2 or 400 cd/m2 brightness is more than enough, but you will need a number far higher than this if your monitor will be exposed to direct sunlight or if it will be on an outdoors environment.
• Contrast ratio: This spec measures the brightness difference between the maximum white and the maximum black the monitor can generate. The higher this ratio is, the better, as you will be able to distinguish between more colors (i.e., better image quality). An LCD monitor with 600:1 rate, for instance, is better than a monitor with a 400:1 one. Units currently available on the market have contrast ratios between 400:1 and 1000:1. There is also a similar spec called “DC” or “Dynamic Contrast Ratio” that presents higher figures, see below. Some manufacturers announce the monitor DC instead of the static contrast ratio. You can’t compare dynamic contrast ratio to static contrast ratio. For example, a monitor with 5000:1 static contrast ratio will have superior quality compared to a monitor with 5000:1 dynamic contrast ratio.
• Dynamic Contrast Ratio (DC): Displays with this capability will lower the brightness from the backlight of the
  LCD display depending on the image being displayed to provide a better contrast ratio. Notice that this is a trick to improve image quality that doesn’t change the monitor’s real (static) contrast ratio. As explained, you can’t compare dynamic (DC) values with static values; they are incompatible. A monitor with a 1000:1 contrast ratio will have a better image quality than one with 2000:1 dynamic contrast ratio with only 400:1 contrast ratio. Some manufacturers only announce the DC ratio, especially when the monitor has a high DC but a low static contrast ratio. When you see monitors advertised with a contrast ratio measured on the thousands, you can bet that the manufacturer is talking about the dynamic contrast ratio, not the real (static) one. So compare static contrast ratio with static contrast ratio and dynamic contrast ratio with dynamic contrast ratio. Dynamic contrast ratio is a desirable feature but when comparing two units with the same DC, pick the one with the higher “real” contrast ratio.
• Viewing Angle: Depending on the angle between the user and the screen, the user won’t be able to see the contents from the screen. The viewing angle indicates the maximum angle the user can stay from the video monitor and still see the screen contents. Usually two numbers are given for this spec, one horizontal angle and one vertical angle, with some models having an upper viewing angle different from the lower viewing angle. Since most users will stay exactly in front of the video monitor, this spec doesn’t make much sense for the average user. But depending on the application (for example, you are going to hang a video monitor on the wall to be used to display information for people passing by or something similar) this spec can be very important.
• Connection: LCD monitors can use two types of connections, VGA (using a plug called D-Sub) or DVI-D. The first one is an analog connection, while the second one is a digital one and thus providing a better image quality. You should use the DVI-D connection for connecting your video monitor to your PC, but you are limited to the kind of connection provided by your PC. Currently all video cards provide two outputs, with low-end and mid-range video cards usually providing one VGA and one DVI output and with high-end video cards providing two DVI outputs. Unless you have an entry-level PC with on-board video that only provides one VGA output, you should use the DVI one. For more information on this subject, please read our Video Connectors tutorial.
• USB hub: Some monitors have an embedded USB hub. This device has nothing to do with the connection between the monitor and your PC mentioned above. This device is added to the monitor in order to make the life of users that have several USB devices on the desktop such as keyboard, mouse, webcam, digital cameras, etc easier. Instead of having several cables coming from your desktop and using several USB ports on your PC you connect everything on the USB ports from your monitor and connect just one cable from the monitor to your PC.