TV resolution

How do you determine a resolution of a conventional or analogue TV? You need to look at both the horizontal and vertical resolution. How do you determine the horizontal resolution? You look at the number of vertical lines on the screen. An illustration of this is to imagine counting the number of picket fences. This constitute the horizontal resolution. The quality of a tv set depends on its horizontal resolution. That means the more pickets you have the higher the resolution.

The vertical resolution is fixed by the format. For example , vertical resolution for NSTC is 525 lines but the actual number of display lines is 480 lines.

Interlacing

TVs feature 30 frames in a second. A NSTC picture frame consists of 480 display lines otherwise known as the vertical resolution. The electron beam traces the 480 horizontal lines on the picture tube from the top to the bottom and from left to right. Now each frame consists of two individual pictures. Each picture either feature the odd lines like 1,3 ,5 and so on or the even lines 2, 4, 6 and so forth. Both contain 240 lines per picture. The odd lines are presented first followed by the even lines. Why are there two separate pictures in each frame? Broadcast transmission is more efficient this way. By displaying half a picture each time, you get save one half of the transmission space. This is known as interlacing.

Progressive Scan

For a progressive scan TV, instead of half a picture shown for each frame, the complete picture is shown in each frame. The electron gun scans the horizontal lines in orderly fashion instead of skipping lines as in interlacing. Not only that, 60 frames are displayed in a second which means the number of horizontal lines have doubled. Resolution is better. I understand motion artifacts such as jagged edges during movement is lessened. Lastly, there is less flicker which means no eye strain or fatigue.