2007-03-12 02:18:26 · 11 answers · asked by andylegendoneill 2 in Consumer Electronics ➔ TVs
Maybe because the companies that make them want us to believe they are bigger than they actually are!!
2007-03-12 02:21:38 · answer #1 · answered by Spence 3 · 0⤊ 2⤋
The very first cathode ray tubes (the tv picture tube) were developed well before the second world war. Their early use was not for what we now know as television.
The flattened front of these things (where the image was projected) was circular so the screen size was simply the diameter of this glass plate.
The first cathode ray tubes used in "mass production" television sets had a bakelite frame around the screen face which was roughly oval. This mask later evolved to the rectangular 4:3 ratio shape that we've become familiar with. The tube behind it was still circular and the corners of the frame extended to the rim of the tube face.
Hence the diagonal measurement of the 4:3 frame = the diameter of the tube. Later tubes became 'flattened' until the screen shape itself became of 4:3 ratio but the tradition of designating screen sizes by the diagonal works very well and lives on to this day. It works regardless of the aspect ratio of the set.
Additional Information, if you're interested.
When a screen size is quoted in inches it means the whole distance of the diagonal across the surface of the screen. Some of this screen will almost certainly be obscured by the mounting framework and trim.
When it's quoted in centimetres it means the length of the visible part of the diagonal. The area obscured by trim and mounting frames is not included.
This means that a screen size quoted in centimetres is more useful for comparing 'equivalent' sets than one given in inches. Sometimes the figure has the letter "V" after it. E.g screen size 88cm (V).
2007-03-14 14:51:50 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Dels is right - all of the others above him are wrong. Cathode ray tubes (CRTs) were invented early in the 1900's and were round. The size measurement for any tube was the diamter of the tube. When the tubes started to become rectangular early in the TV era, manufacturers used the largest measurement - diagonal - to state the size of their tubes.
Specifically, the measurement is between the bolt holes on the brackets at the corners of the tube, NOT the visible face of the tube. Some manufaturers extended the size by using bigger brackets. Because they measure between the bolt holes, the measurement is bigger than what you actually see on the screen. This is why when looking at computer monitors, for example, you see text like "21-inch monitor (19.8-inch visible)". 21 inches is the bolt-hole distance, 19.8 inches is the visible screen measurement.
2007-03-12 11:08:08 · answer #3 · answered by Steven D 5 · 0⤊ 0⤋
Because the aspect ratios are different for conventional and widescreen TVs.
For instance, if you measured from side to side, a 20" 4:3 TV would be bigger than a 20" 16:9 TV. And if you measured up and down, a 20" 4:3 TV would be smaller than a 20" 16:9 TV. Measuring on the diagonal standardises the categories.
2007-03-12 09:32:02 · answer #4 · answered by maryavatar 4 · 0⤊ 2⤋
Goes back to when T.V. was first made. The original cathode ray tubes were round and the measurement was the same in any direction.When the first rectangular tubes were made the CRT makers quoted the maximum measurement for the screen size,being corner to corner. This was in the 1950's and has been the norm ever since.
2007-03-12 09:34:47 · answer #5 · answered by Anonymous · 1⤊ 0⤋
If tvs were measured side to side or up and down I would give a true defintion of the size. For instance widescreen tvs are obvouisly wider than they are tall so do you say it is 20" or 39" assuming 16:9 ratio.
2007-03-12 14:05:45 · answer #6 · answered by maybayus123 3 · 0⤊ 1⤋
tv's are built to either 4:3 (4 units wide and 3 units high) normal screen or 16:9 (16 wide and 9 high ) wide screen
since all tv's at one point were the same (4:3) it was easier to give the diagonal measurement than to explain the 4:3 measurements (asnted in another answer below)
the measurement has remained in place with the advant of wide screen tv's (16:9) and iwll remain until a newer measurement is in place (ie : square feet or invhes of viewing area)
2007-03-12 14:15:04 · answer #7 · answered by mrdg90 4 · 0⤊ 1⤋
Because it gets all messed up with widescreens, and if they mesure from side to side then it would be two measurements. and with corner to corner it is only one.
2007-03-12 09:29:00 · answer #8 · answered by steven z 3 · 0⤊ 1⤋
the old screens showed a 4:3 picture measuring the diagonal is basic Pythagorus
2007-03-12 09:29:15 · answer #9 · answered by BillyB8 6 · 0⤊ 2⤋
it will be too complicated to specify think bout it 15X12 or
17 in which on do you prefer and before there was just a standard tv size until now that there are various sizes.
2007-03-12 09:28:39 · answer #10 · answered by Yeahbabe 3 · 0⤊ 2⤋