The Difference Between Analog and Digital
The key difference is that digital will give you much higher video quality and resolutions compared to analog.
Types of Digital Cables
Note the DVI-D in the cable in the picture here. The “D” in DVI-D stands for Digital, so it can only be used to connect to a fully digital monitor. Now look at the DVI-I cable, you will notice there are 4 extra little pins on this one. The “I” in DVI-I stands for Integrated meaning that it integrates both digital to digital as well as analog to analog connections.
Analog vs Digital
When comparing analog vs digital, think of it this way. Analog video signals are in the form of waves (like a radio wave). Digital video signals are in the form of 1’s and 0’s (it’s either on or it’s off). Before either type of video is displayed on your monitor, it goes through a series of stages. The creation stage (video recording or animation), then the storage stage (on tape, DVD, or hard drive), and finally the display stage (appearance on a TV or monitor).
A video image can travel through all stages as either analog or digital, or it may be converted from one to the other and back again. Such analog/digital or digital/analog conversions reduce the integrity of a video signal. However sometimes conversions are unavoidable without the use of video adapters.
Because analog video is displayed via a series of scans and digital video is displayed via light and color intensity on fixed dots (pixels), conversions can produce signal loss and errors. DisplayPort, DVI or HDMI are all digital.
No Adapters When Possible
Ideally, a video signal would be analog or digital from one end to the other using no adapters. This means from the back of your digital video card directly to your digital monitors, digital straight to digital.
Most computers now are purely digtal. But when adapters are used, the video signal must be converted, either from digital to analog or analog to digital. These two conversions create a lot of signal loss that degrades video quality.
In summary, always connect end-to-end via digital when possible. You will get a far superior image quality to your monitors when you connect digital all the way. In other words, the connection from your video card all the way through to your monitors, should all be digital.