The Difference Between Analog and Digital
Analog video connections and devices are quickly becoming a thing of the past giving way to all digital connectivity. If you are buying a new computer or monitors make sure everything connects digitally.
The key difference is that digital will give you much higher video quality and resolutions compared to analog.
Compare Analog to Digital
Note the DVI-D in the cable in the picture here. The “D” in DVI-D represents digital meaning that it can only be used to connect to a purely 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 video signals are in the form of waves while digital video signals are in the form of 1s and 0s. However, before either video format is displayed on your video display, video images first go through a series of stages: The creation stage (video recording or animation), the storage stage (on tape, DVD, or hard drive), and the display stage (appearance on a TV or monitor).
A video image may 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 and degrade video quality and should be avoided when possible, however most conversions are unavoidable without the latest “expensive” video components.
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 produce signal loss and errors. Ideally a video signal would be analog or digital from one end to the other. However, because digital signals can be copied, stored and transmitted more accurately than analog signals, the ideal video system would be digital from end to end.
Most computers create, store and transmit video signals digitally, but before sending these signals to a video display (a monitor) they are usually converted to analog signals and signal loss occurs in the conversion. Once digital video display devices hit the market, two conversions took place, one from digital to analog (within the computer) and another from analog back to digital (within the video display). These two conversions create a lot of signal loss that degrades video quality.
In summary, when possible always connect end-to-end via digital when possible. You will always 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.
Also see: M.2 SATA, mSATA, eSATA, SATA Express | How Fast is USB 3.0 | HDMI vs DVI | DVI-I vs DVI-D | What is DisplayPort | Monitor Connections