The Aspect Ratio defines the shape of the rectangular picture in a TV set. It is the width of the picture relative to the height. Our standard TV picture, in terminology used by that industry, is 4 units wide by 3 units high, or 4:3 (read as 4 by 3) in aspect ratio. There is more than one way to express an aspect ratio. In film terms the width of the screen is 1.33 times the height. Divide 4 by 3 and you get 1.33333... It has an aspect ratio of 1.33:1 (read as 1.33 to 1). Since the :1 is always the same it is often dropped for the definition. We then say that the set has a 1.33 aspect ratio instead of saying it has a 1.33:1 aspect ratio. This is an easy system to use in that the larger the number the wider the set. A 1.78 set is wider in aspect ratio than a 1.33 set. Of the two numbering systems, you might initially think it's easier to use the 4:3 instead of 1.33:1 or just plain 1.33. That works until you get to multiple aspect ratios. Then it becomes difficult to determine what the numbers are telling you about the shape of the picture. Picking on two widescreen sets that have been available in the U.S., which is wider, one that is 16:9 or one that is 16:10.5? Asking the same question in decimal systems makes it much easier to answer that question. Which is wider, 1.78:1 or 1.52:1? The decimal system makes it much easier to determine the correct answer. 1.78 is wider than 1.52. Since there are a number of aspect ratios currently in use, not all of which can be expressed as whole numbers, the decimal system is by far the better choice. The film community has many more aspect ratios and has therefore adapted the decimal system to describe the shape of the picture. There are currently two standard TV aspect ratios in the U.S., 1.33 (4:3) and 1.78 (16:9). The 1.52 aspect ratio set is sort of a compromise in the transition from one system to another. They alter picture geometry to get either 1.33 or 1.78 to show up on the 1.52 screen. In the DTV world we’ll see a bit of 1.55 or 14:9 as another option in the compromise. That’s what will be done to 1.33 images as they are upconverted to a raster that is defined as 1.78. Some of the top and bottom of the 1.33 image will be cut off so that the image can appear to be wider on the 1.78 set. There will still be slight black bars on the left and right edges of the image. Several manufacturers are advocating 1.85 because it's a common aspect ratio for many American movies. The Director's Guild has called for a study of making 2:1 the shape of new video displays. It is also possible that some day the high definition active picture area will be redefined as 2.35 from its current 1.78 aspect ratio. This is just another extension of defining the 1.33 aspect ratio of standard definition television to 1.78 in the DVD format. If the future of television is widescreen, is one aspect ratio better than another? Knowing that we will have to accommodate the 1.33 aspect ratio for some time to come, the question becomes how wide can we go and still deal with the 1.33 image in the center? The resolution of current display technology would suggest that 1.78 is the upper limit of our current capability. The 1.33 image is compromised by only being able to use the resolution in the center of the display and images wider than 1.78 can’t use the resolution available at the top and bottom of the display. Some of these problems can be partially resolved by the use of high quality scalers and displays that far exceed the resolution of the source signal. That gets tough to accomplish as the resolution of our source signals goes up. It looks as if the 1.78 imager has a long life ahead of it as a compromise between 1.33 and all of the wider aspect ratio pictures. The majority of Video Essentials on DVD is produced in 1.33. Only Title 20 is in 1.78.