Many LCD monitors now come with both an analog (VGA) and a digital (DVI) connection.  What is the difference?  Which one makes for superior image quality?

There are two major types of computer monitors: CRT, which based on the same 100-year-old cathode-ray-tube technology as the first television,  and LCDs, which are based on newer, liquid-crystal technology.  Although CRT monitors are still optimum for some tasks, LCD look slicker, take up less desk space, and can offer sharper image quality, and as a result, they have begun to dominate the market.  Most CRTs offer only VGA connection, but more and more LCDs offer both DVI and VGA inputs.  Which one should you use?

Let's take a step back.  A CRT, or cathode-ray tube, monitor is an iherently analog device, while computers are purely digital device.  How does a 20th century analog appliance talk to a 21st century digital machine?  They do so via a video or so call graphic card.  Most computers have at least one analog input, which is sometimes labeled VGA (for video graphics array) or D-SUB, on the back of the computer.



The graphics card converts the computer's digital signal to an analog one, which it conducts to the monitor via an analog (VGA) cable.  Without getting into too much detail, the CRT monitor takes the analog signal and uses electron guns to manipulate phosphors and, well, it turns the signal into an image.  However because of the conversion for digital to analog, in general, CRT monitors deliver less accurate image quality than LCDs.

An LCD (liguid-crystal display), on the other hand, like computer, is a digital device.  Manufacturers are increasingly putting both an analog (VGA) and adigital (DVI) connection on LCDs.  When connected via VGA connection, a LCD is vulnerable to the same distortions that affect CRT monitors.  However, when via a digital connection, often labeled DVI (for Digital Visual Interface), no digital-to-analog conversion is required, and there should be no loss or corruption of the signal.  As a result, when running at its native resolution, a LCD should give you a cleaner and crisper image then you'd see on a CRT.



CRTs rarely provide suppot fo digital signals; DVU support is found primarily on LCDs.  However, the advantage of digital signals for LCDs is of somewhat less impotance now than it was a few years ago.  Analog signal processing has improved to the point where major differences in image quality can be difficult to detect, unless you are a pro photographer, a prepredd professional, or someone else who needs superprecise, top-notch image quality, you should be fine using a CRT or an LCD on a VGA input.

If your LCD have a digital connection, you'll need a graphics card that have a DVI-I or DVI-D connector to take advantage of it.  You'll also need t DVI cable (many LCD monitors come with only a VGA cable).  DVI-D refer to a digital-only connection, and DVI-I means that connector can carry either digital or analog signals.

Now, there is external device, the USB 2.0 external graphics card VGA & DVI interface enables you to hook up to your LCD digital connection at an affordable price.  You can look into ebay auction site for the device.