A wide screen
TV is smaller than a narrow one
The Sunday Nation
Nairobi,
21 March 2010
Flat screen LCD
televisions are becoming more and more popular these days. Even the
prices have come down drastically from several hundreds of thousands of
shillings a few years ago to just a few tens of thousands. I have seen
some selling for less than Sh25,000.
As people migrate
from the old TV “box” to the new “tablet” flat-screen format, an
interesting question has come up: is a 27-inch box the same size as a
27-inch tablet? The quick answer is of course yes! After all, 27 inches
are 27 inches whether measured on a box or a piece of paper. All the
same, let us take it through some analysis.
The stated size of a
TV is the length across the diagonal of the screen. The problem here is
that the old box is almost a square shape while the new tablet form is a
wider rectangle. In order to compare these different shapes, we must
find a way of calculating the areas of the screens in square inches.
The area of a
rectangle is found by multiplying the width by the length. Now TV
manufacturers don’t usually state the dimensions of the screen, but that
is not a big problem since they are made standardized ratios. The ratio
of width-to-length (height) in the old box format is 4-to-3.
Thus if it is four
inches wide, it will be three inches tall. An interesting outcome of
this is that for it to have right-angled corners, the diagonal of such a
screen would have to be 5 inches long.
This 3-4-5
relationship for right angles was probably the reason why the initial TV
screens were made in the ratio of 4-to-3: it makes the determination of
screen dimensions very easy.
Thus; to get the
width you divide the diagonal by five and multiply the result by four;
for the height, divide by five and multiply by three. Using this
procedure, it turns out that, a 27-inch box is 21.6in wide and 16.2in
tall. This gives an area of about 350 square inches.
The new tablet
wide-screen format has a different width to height ratio of 16-to-9. Now
this is an awkward ratio; a screen that is 16in wide by 9in tall would
have a diagonal of 18.357559750685819298491719518707 inches!!! OK, let’s
call it 18.36in; after all we are friends, aren’t we?
Using the same
procedure as before (but, of course, applying different ratios!), it
turns out that a 27-inch flat screen is 23.5in wide and 13.2in tall.
Thus its area is about 310 square inches.
Clearly then, a 27-in
“wide-screen” is 40 square inches smaller than a 27-in “narrow-screen”.
The next obvious question is: if you wanted to upgrade from an old
27-inch box, what size of a flat screen would give you the same size of
image?
The answer is that
you need a wide-screen that is the same height as your old box. That
way, a picture in the 4-to-3 format will fit inside the new screen but
leave blank bands on the sides.
Now we have seen that
a 27-inch old style box is 16.2 inches tall; it turns out that a 16-to-9
flat screen of this height would have a diagonal measuring 33 inches.
That gives a good conversion factor: if you want to retain the same size
of screen when migrating to the new format, then multiply you old size
by 1.222
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