High Definition TV - Are We Being Conned?
When I decided to replace my glass 36 inch TV with an up-to-date flat panel, I decided to do a bit of research - mainly because there seemed to be some pricing disparity between "same-manufacturer" models of the same screen size. Just what was the extra cost for, when the sales person in the high-street shops couldn't explain it- maintaining that they were both high definition. No mention was made of the various degrees of high definition - maybe they just didn't know, or maybe they were keeping quiet so as to sell more TVs - maybe I'm cynical but I'd guess the former is more likely. Irrespectively of which, many purchasers seem to have been conned.
First came a visit to both Currys and Comet, notebook and pen in-hand. I didn't really have a hard-and-fast budget but I didn't want to be taken for a ride. I do know someone who bought a very expensive 50 inch (or was it 60 inch?) TV two or three years ago. He insisted was high definition. It turned out not to be. Lessons are often best learned from other folks misfortunes - and I didn't want to be taken for a ride.
Once I'd gathered a list of the various makes/models, with prices I sat down and started digging.
The first thing that I discovered that there are no less than four different resolutions that qualify for the description "HD Ready". These are 720i, 720p, 1080i, and 1080p - in ascending order of "high definition". When passing Curry and Comets I went in and asked for an explanation of the difference. Yes - you've guessed it - I was met by a glazed look - but to be fair in both shops the sales person said that he would find out and off he scuttled. This was so similar in BOTH shops that I couldn't hide a smile. In both shops the salesperson returned and, with a pleased smile, informed me the 720 is one resolution and 1080 is another resolution. "Err... what do the figures mean?" I asked. In both shops (the staff must be trained at the same place) the absence of explanation was the same. It was uncanny how similar these exchanges were. "What about the I and the P?" I went on. I was now feeling a little guilty because I already had an idea what the figures and the suffixes meant. Again the same response at both shops - "The I and the P are the way the picture is displayed", was the reply, which I suppose was true. At this point (in both shops) the salesperson began to look somewhat uncomfortable, and was glancing around - whether to find another customer to escape to or to find someone to help him out, I'm not sure. Anyway, feeling a bit sorry for him I politely thanked him and said I'd think about what he'd said before making my mind up (it was the same in both shops). Obviously they must both be on some sort of bonus scheme as the both requested me to ask for them by name when I came back. I won't be so cruel to mention their names. Nor did I return.
Anyway, let me now explain what the sales persons SHOULD have known. It might help others not to buy something which isn't at the full Hi-Defintion standard.
Some of us older people will remember the TV test cards which were broadcast after the programs were shut down late at night. They were intended to aid the TV installers in properly setting up the TVs - though thinking back what TV installer would be installing and setting up a customer's TV between midnight and six in the morning? The test cards allowed all sorts of things to be set up which aren't relevant here. I only mention them because much of the test card picture was taken up by parallel lines in various axis, so a TV could be assessed on "lines of resolution". Glass TVs (originally) had 405 horizontal lines, then later 625 horizontal lines. Because you couldn't discriminate below this figure, top to bottom of the screen, the lines of resolution were measured across the screen.
Things have now changed with the disappearance of glass TVs. But the "lines" bit is still relevant when considering a flat-screen's resolution. Easiest way to look at it is the number of horizontal lines which will display the picture. So a 720i/720p will have 720 horizontal scan lines - not much more that the old 625 line standard, but 720 is STILL classed as high Resolution ("HD Ready"). Obviously 1080 scan lines is much much better. But here comes the rub. To be able to display a high resolution picture (at 1080 lines) the native resolution of the display itself MUST be capable of displaying 1080 rows on the screen. Now here's the problem - a lot of so called 1080i/1080p televisions CAN NOT put up that number of lines. Before we look at a particular example, we should remember that if we are going to display a wide-screen piture of a 16:9 ration, then we must be able to display 1920 vertical lines across the display as well as the 1080 lines in the other axis. And again, a lot of so called 1080i/1080p Hi-Definition TVS CAN NOT disply this number of vertical lines. So how do we know.
As an example, shall we take a very popular plasma screen TV - the Samsung PS50Q97HDX? If we go here where the specification is reproduced from the manufacturer's product sheet, under Display we see that the native resolution of this TV is only 1365 x 768. So how can this so called 1080i Hi-Definition TV display when it simply can NOT display a 1920 x 1080 picture. And here is where the claim that it is a 1080i Hi-Definition TV falls on its backside. True, it receives a 1920 x 1080 picture but it can NOT display it without fudging it because it has not got enough pixels to do so, and the result - by the basic laws of physics - is that the VERY BEST that you will see on the screen is a picture of only 768 lines. So the claim that it is a 1080i TV is at the very least flawed.
Some other Samssung TVs do indeed support the REAL resolution of 1920 x 1080 - an example of which, the Samsung LE40M86BD, can be found here. This model is, incidentally, the television that I eventually purchased - but not from either Currys or Coment with their high prices (see my webpage Buying Stuff)
OK, so having sorted out the 720/1080 bit - what about the "i" and "p" suffix. The former indicated that the picture is Interlaced, and the latter that the whole picture is displayed Progressively. An interlaced picture "paints" every odd numbered line, and the goes back to fill in the gaps with the even numbered lines. Why should this make a difference? Well, if you're displaying a still picture with no movelment within that picture - no difference whatsoever, But if you have a moving object within the picture frame, then after the first scan of the interlaced picture the object has moved before the next line is painted and we get what is known as a "movement artifact" - meaning that the resolution of the picture is compromised. That is why the 1080p is the only FULL HD standard.
But hold on - not all is lost (at the current time). Sky HD only broadcast to the lower High Definition stanard of 1080i. And there again, if you're going for Blue Ray, the current crop of Sony Blue-Ray players only give you the lower resolution standard of 1080i. If, though, you go for a Toshiba HD DVD player you'll get the FULL 1080p high definition - arguably a good reason NOT to go for Blue-Ray - at least until Sony produce a Blue-Ray player that supports the FULL HD standard of 1080p. But there again - the major movie companies (influenced no doubt by the gullible public) have recently decided to go for Blue Ray. More of this on the High Definition TV page.
Having said all that, the REAL issue is that if the native resolution of the HD TV that you have bought only provides (say) 768i then you're MOST DEFINITELY NOT getting full High Defintion - nor anywhere near the 1080i/1080p we should be expecting.