Digital Video Interface

Most people think that DVI is vastly superior to an analog VGA connection for a LCD flat panel. Those people are right.

It makes sense for DVI to be better. With DVI, images are inherently sharp because each pixel on the monitor reflects one pixel from the computer. In fact, there is no reason why non-DVI LCD panels should still exist since all LCD panels are inherently digital. An analog-only LCD panel actually requires additional circuitry to convert the information back to the digital format – with DVI, there’s a direct connection. More importantly for you, there’s no meaningful price difference. The cheapest 17” non-DVI monitor is $205 and the cheapest 17” DVI monitor is $220. If your budget is so tight that you cannot afford the $15 difference, you shouldn’t be spending your money on computer equipment in the first place. If there’s one absolute of buying an LCD monitor, it is to get a monitor with DVI support. As long as you stick with a DVI panel, your monitor will be sharp.

There are two myths when it comes to DVI. The first is that the analog VGA output allows better color. This is false and we’re not sure where the misconception comes from. With exception of $2000 exotic LCD panels, monitors can only work with 24-bit color. This means that the monitor can only consider integer values from 0 to 255 for red, blue, and green information. The DVI interface is perfect for transmitting these numbers. With the VGA, an “analog to digital converter” has to measure the voltage of the signal to figure out what integer is closest to the measured input.

The second myth is that analog VGA is just as sharp as DVI on today’s monitors thanks to today’s improved analog- to digital converters. This is a false statement perpetuated by well-intentioned but inexperienced reviewers. They’re well-intentioned because they’re trying to help you save money by saying that there’s no big difference – they’re hoping that there’s no difference. We want to help you save money too – but instead of telling you to go with a lower-quality but lower-priced monitor that you’ll need to upgrade in a year or two, we want to help you find the right monitor so that you only need to buy it once and not have to upgrade for another 5+ years.

There definitely has been an improvement in LCD panels running analog VGA, but it’s not due to the analog to digital converter. It’s due to improvements in sharpening algorithms. Let’s explore this using a once top-of-the-line Samsung 915N 19” LCD panel with an 8 ms pixel refresh.

VGA - no sharpening

VGA - automatic sharpening

DVI – no sharpening

Target image

As you can see with a DVI signal, there’s no need to sharpen. If pixel #24609 is supposed to be black, the monitor shows black. This isn’t the case with analog. The unsharpened image reflects what’s really being received by the monitor. As you can see, it’s a terrible image. By applying a sharpen filter to the signal, it’s possible to increase the contrast between pixels. The problem is that this adds artifacts to the video. That’s the default sharpening set up by the “auto-adjust” feature. If you turn down sharpness to avoid the halo, the text gets blurry. Note that this test was done with a high-end analog-only LCD monitor and a modern flagship GPU – a budget panel, or a budget video card won’t have anywhere near as good of a picture. On the other hand, a budget DVI panel and budget DVI video card will essentially look just as sharp as a high-end setup when it comes to text.

Although today’s signal processing does a reasonable job and makes analog VGA usable, with a DVI connection you wouldn’t even need any signal processing to begin with. Since any video card capable of playing modern games is going to have a DVI output, we see no reason not to get a DVI panel. Remember, you don’t save money by getting a low-priced product that’ll need replacing in a few years – you save money by getting a low-priced product that has the endurance to last.