How wide-screen TVs display smaller pictures

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

12 November 2006

Kimani John says that he has notice that there are two types of TVs in the market. Some have square screens and others are rectangular. He asks: “How can a rectangular TV display the same image as a square one?”

The simple answer is that they don’t have similar images. There are two video picture size standards describing the ratio of the width to the height of the image – the aspect ratio. The narrow screen is not exactly a square; it has a ratio of 4 to 3 (4:3). Rectangular screens have an aspect ratio of 16:9.

Now, normal television broadcasts are on the 4:3-standard. There are three ways of displaying these images on a wide 16:9 screen. The first one is to show the full image unchanged. This leaves two blank vertical areas on either side of the screen.

The second method is to fit the width of the image on the wide screen. To do this, the top and/or bottom portions of the image must be chopped off because the space will not be enough.

The third method is to stretch the image to fit on the screen without cutting off any part. This distorts the picture and things (especially people) look “fatter” than their true size. Most of the wide screens in the show rooms are set to this mode. If you look carefully, you will notice that things are broader than usual.

In contrast, High Definition Television (HDTV) broadcasts are on the 16:9 aspect ratio. HDTV is not yet available in Kenya but, with the advent of digital TV in the country, the 16:9-standard may become common place in the near future. When a 16:9 image is displayed on a 4:3 TV, it fits the width and leave blank areas in upper and bottom parts of the screen.

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 Peter Wakaba has sent in an interesting anecdote and asked me to comment. It goes thus: “A man died and left his cows to his three sons. He had 17 cows which were to be divided as follows: The eldest son gets a half of the total, the second a third while the youngest gets a ninth. After trying and finding it impossible to share the animals, the sons consulted their uncle.

“The uncle nodded knowingly and solved their problem this way: He got one cow from his herd and added it to the 17 to make 18. Now, a half of 18 is 9, a third of 18 is 6 and a ninth of 18 is two. So the three sons got 9, 6 and 2 animals respectively. But the total given out (9 + 6 + 2) comes to 17. So the uncle was left with one cow – the same one he had given to the brothers – which he returned to his herd!”

My comment is this: That is one intelligent uncle, but the will was inconsistent. A half plus a third plus a ninth do not add up to one. There is an eighteenth fraction which was not allocated to anyone. Perhaps that’s why one cow remained.