Overview of High Definition

High definition (or HD) is a term that refers to the level of clarity an image (or group of images) displays in a photograph or on screen.  High definition technologies have the ability to enhance colors, create smoother motion on screen, and display what viewers know as a wide screen view.  More specifically, HD is a measure of an image's resolution and the better the resolution, the better the picture.  Resolution is determined by the number of lines that are shown in a screen and the number of dots within those lines, or pixels.  Though high definition photography, film, and television involve achieving the same ultimate effect, different equipment and processes are used for each one.  This discussion is focused on film and television.  

HD television and video are becoming increasingly popular considering the noticeable difference in overall quality compared to standard versions.  Unlike standard television sets, HDTV is broadcasted digitally by signals that allow pictures to appear up to five times sharper or in other words, with much higher quality resolution.  Before high definition technologies were around, TVs were only capable of displaying about 480 lines of resolution.  Now, they can display between 720 and 1,080, which are currently the two most common formats used by broadcasters.  Though the 1080i format is supposed to be that much more advanced, both are of excellent quality and are actually better for opposite reasons.  The 720p is able to capture more rapid movement while the 1080i format captures more detail in slower movement.  This is because they scan lines onto the screen in different ways.  The "i" in 1080i stands for interlaced, which means that every other line is scanned first, then all the lines in between.  In comparison, the "p" in 720p stands for progressive and means that the lines are scanned in order creating a completely smooth image, free of any distracting flickers or pauses.  Therefore, progressive scanning is better.