Oh VGA, You’re So Analog
First, we will explain how a VGA can garble data. VGA connectors are analog. Computers are obviously digital. Some data gets lost in translation (digital to analog conversion, or DAC). This was no big deal when we were using CRT (cathode ray tube) monitors, since these are analog as well, and the data had to get lost somewhere. If you have a digital monitor, which are almost everywhere by now, it is obviously better to preserve the signal as digital. This prevents errors as the data goes from digital to analog and back to digital on the screen
The other problem is harder to nail down. This digital to analog fudging means we can’t really compare apples to apples in terms of bandwidth and resolution. But we can see if the apples are starting to rot and we should get oranges instead. The maximum resolution claimed for a VGA connector is 2053 x 1536, which sounds like a lot. The 4:3 aspect ratio, while indicative of the age of the standard, is not important; we’re looking at how many pixels it can carry. For reference, if we apply the current 16:10 standard, that puts it about halfway between the 1920 x 1200 WUXGA specification used for 22-28" monitors and the 2560 x 1600 WQXGA spec used for 30" and larger screens.
So (ignoring DAC issues) VGA should be plenty unless you have one of the highest resolution screens available, usually found only in front of graphics editing professionals, right? If you have the hardware for it, you can definitely turn your settings up that high, but it won’t look very good. Maybe if you were using a 6" long gold cable with 3" wide lead shielding it would look pretty good, but still not as good as DVI.
The analog signal carried by a VGA cable is subject to significant degradation. You don’t just lose on the DAC; the data that comes out of your computer is then assaulted by all kinds of electrical noise and every inch it travels along the cable. In most cases, you will actually notice a difference if you use a 6 or 3 foot long cable, particularly if the longer one spends more of its trip running around alongside other cables behind your computer.
Since the VGA signal loses a lot of the data’s finer points, it is only suitable for far lower resolutions, as we explain later on.