DVI-D is Digital Video Interface – Digital. Using DVI-D is the highest quality image because it is all digital all the way, and there are no exceptions. This is perfect for home theaters, or a big budget shows, where going all digital is ideal.
The real-world trouble with DVI-D is that it cannot be used to connect to an analog source, which is the majority of displays/projectors encountered today. (I should note that I did some research and there are a few DVI-D to VGA converters are out there, but they cost $200+). This limitation of only connecting to other DVI-D equipment is a major limitation for us with the wide range of euqipment we may be using.
Looking at the connector it is easy to see if it is DVI-A or DVI-D. DVI-D does not have the 4 additional connector pins around the slotted connection (on the right side of this image).
Troy @ TLC