VGA and DVI connectors are used to transmit video from a source (like a computer or tablet) to a display device (like a monitor, TV or projector). The main difference between VGA and DVI is in the way the video signals travel. VGA connectors and cables carry analog signals while DVI can carry both analog and digital. DVI is newer and offers better, sharper display compared to VGA. You can easily tell them apart because VGA connectors (and ports) are blue while DVI connectors are white.
|Stands For||Digital Visual Interface||Video Graphics Array|
|General Specification||Hot pluggable, External, Digital video signal, 29 Pins||Not hot pluggable, RGB video signal, 15 Pins|
|Signal through cables||There are three types of cables:- DVI-A: Analog only DVI-D: Digital only DVI-I: Digital and Analog.||Analog|
|Display||Cleaner, faster, more precise display with hardware that supports it properly.||The maximum resolution claimed for a VGA connector is 2053 x 1536, however due to signal conversions and the influence of electrical noises the output is not comparable.|
|Compatibility||Can convert to other standards like HDMI and VGAs.||VGA to DVI and VGA to HDMI converters available.|
edit Quality of the signal
DVI offers a higher quality signal compared to VGA. The difference is especially noticeable at higher resolutions. The video quality is a factor of the mechanism of operation and the length and quality of the cable.
edit Mechanism of operation
From a user's point of view, both connectors work in the same way: devices have female ports and the connector cables have male endpoints. The signal is transmitted from the source device via the port to the connector cable and the desitnation, which is a display device.
VGA connectors transmit analog signals. The digital video signal received from the source is converted to analog to be transmitted via the cable. If the display device is an old CRT (Cathode Ray Tube) monitor, it accepts an analog signal. However, most display devices are now digital; so they convert the VGA connector's analog signal back to digital. This converstion from digital to analog and back results in a degadation of video quality for VGA connectors.
For both VGA and DVI connectors, signal quality is impacted by the quality and length of cables. A cable carrying a signal is impacted by crosstalk which occurs when the signals in one wire induce unwanted currents in adjacent wires. VGA cables are more susceptible to electrical disturbances and noise compared to DVI. Always use high quality cables that provide good, thick insulation.
Signal degradation is worse for longer cables; again, VGA cables are more susceptible to this problem. DVI cable lengths up to 15 ft work for displays at resolutions of 1,920 × 1,200. Cable lengths up to 50 ft can be used with displays at resolutions up to 1,280 × 1,024. For longer distances, the use of a DVI booster is required to mitigate signal degradation.
The following video compares the output of using a DVI vs a VGA on a game on HP 2510i 25" monitor:
edit Types of connectors
The VGA connector is also called RGB connector, D-sub 15, mini sub D15, mini D15, DB-15, HDB-15, HD-15 or HD15. It has 15 pins. There is only one type of VGA connector and it is blue in color.
In contrast, there are different types of DVI ports.
- DVI-D is the digital format connector. It is the most popular format used for connecting digital LCD monitors to DVI graphics cards. DVI-D can come in single-link and dual-link forms. The dual link form provides twice as much power and delivers the data more rapidly than the single link kind. So dual-link may be used for larger monitors. Here is the layout of the pins.
- DVI-A is the analog version of DVI. It is used to carry signals from a DVI graphics card to an analog display, for example a CRT monitor. There is a digital to analog conversion applied here, but this still gives higher-quality results than a standard VGA cable. Here is the layout of the pins The analog pins are the four that surround the flat blade as shown in the picture.
- DVI-I is the integrated format which caters for both digital and analog equipment. This doesn’t convert a pure DVI-D output to something a DVI-A device can use. But it will act as a DVI-D cable or a DVI-A cable according to your needs. The real benefit is that you don’t have to use two different cables if you use both digital and analog displays.DVI-I also come in single-link and dual-link forms. DVI-I dual-link has 29 pins
Here is an excellent video that compares the various standards (VGA, DVI, HDMI, DisplayPort etc):
edit Products and prices
A plethora of connectors and adapters are available. People are often constrained by the ports available on their computers. Older PCs may only have a VGA port and new monitors may only have a DVI port. In such cases you may need a VGA to DVI adapter to connect this PC and monitor. It should be noted that you cannot get DVI quality by using a VGA to DVI adapter. While some quality issues like signal degradation in longer VGA cables can be avoided by using an adapter near the video source, the digital-to-analog conversion necessitated by the VGA port does degrade signal quality.
Converters also differ in quality and price. Here are some prices for DVI and VGA accessories (including adapters starting from $5) on Amazon.com: