Adam

Adam J Purcell Ponders… Stretch-o-Vision™

Published: 7th October 2002

We've all seen it. One day, perhaps feeling rich, we go down to the local electronics shop and spy a few shiny new television sets. But what's this? Why, on these otherwise fantastic looking new widescreen TVs, does everyone on telly now look shorter and fatter than we remember? They look okay on those old squarer sets in the poorpers section but not on the widescreens. Celebrities are always complaining how television makes them look fatter and they are happy to regale us with the numerous tales of Joe Bloggs stopping them in the street and expressing surprise at how much taller or shorter they are in real life. Do these great new widescreen TVs make this situation worse, something magically different about widescreen (16:9) compared to the old 4:3 sets?

Chances are it is something much more mundane than a simple optical illusion. Chances are we're watching Stretch-o-vision™.

Now I'm not normally one to rant (too much) but what possesses people with widescreen TVs to stretch normal 4:3 pictures into 16:9 - completely different aspect ratios? I assume it is not because they prefer to see short fat people. Though, perhaps they do - good for their self esteem, maybe? On the other hand, it could just be that their brain's object recognition system can't distinguish between short fat people and tall thin ones. It also could be that these people are just absolutely determined to make full use of the screen real estate, they paid good money for widescreen so they are jolly well going to use it - even it does mean distorting the picture. But, I think the real reason is that people are simply ignorant on how to use their TVs properly - they are used to something they just press a button to turn on and a couple of other buttons to select the channel. That's a pretty damning indictment of the couch potato culture the television has created over the decades.

Okay, I should probably give you some concrete examples so you know what I'm talking about. Below you can see some 'test cards' of the awesome foursome that are the Staggering Stories Team. The image was originally shot in 4:3 aspect ratio (i.e. the same as a traditional television set).

 

Figure 1

Native 4:3 – How we should appear

Here we are in our native state, unstretched and how we appear in real life (except Tony, at the back, who has become a bit wider since this shot was taken last year!)

 

Figure 2

Native 4:3 on a widescreen 16:9 set – as it should appear

Here's the same picture as it should appear on a widescreen TV. The picture is still 4:3 but is centered in the 16:9 frame. This is how it should be done - any non-widescreen television programming should be neatly centered on the widescreen set.

 

Figure 3

Stretch-o-vision™ - 4:3 stretched to fill the entire 16:9 screen

This is what I hate - when the 4:3 picture is stretched into a 16:9 aspect ratio. We all look short and fat. Well, actually I don't think I look too bad, always thought I should have been built like a tank! But no, on the whole a completely hateful distortion of geometry and reality - just look at the square and the circle.

 

Figure 4

Zoomed – 4:3 with the top and bottom trimmed to fill 16:9 screen

It should be obvious by looking at the pictures that there is simply no way to make a 4:3 image fit exactly into a 16:9 space without either causing stretch distortion or chopping the top and/or bottom off the picture. Obviously this method means you are losing part of the picture, effectively zooming in on it, which I'll mention again in a bit when I talk about Anamorphic images.

 

Any widescreen TV worth it's salt will have a feature that enables the TV to choose the correct aspect ratio automatically. This sometimes goes by the name of 'Auto' - imaginative these TV engineers. If you want to show off that shiny new widescreen TV perhaps you should enable this feature so people don't look at the picture and think - ergh, Carol Smillie's fingers look much thicker on this rubbish TV set! Or worse still - yeah that was a great wedding video but weren't you lot a bunch of porkers back then?!

 

Anamorphic Video

Widescreen television pictures, at least here in the UK, are a kludge. The system was not designed to broadcast anything but 4:3 pictures, in our case PAL (there are other systems, such as NTSC used in the USA and elsewhere, but all are 4:3 based). There are other systems coming along such as High Definition TV but as that has little prospect of appearing in the UK for quite a while I won't mention it here again!

In the UK you can only get true, designed for widescreen, video via a digital system. Be that Sky Digital, ITV Digital (or whatever it will become after the collapse), Digital Cable and, indeed, DVD. These can all provide what is called an anamorphic picture.

 

Figure 5

Anamorphic Widescreen – our testcard now designed with widescreen in mind. Notice our extra guests at the sides (our friends Velma and Willow, who obviously couldn’t be with us that day so I added them in post-production!)

Without wanting to get into too much technical detail, you can think of your television picture as being made up of a collection of horizontal lines, going from left to right across the screen. Each line is distinct and separate from any above or below it. You could also think of these lines as being rubber bands, hooked in to the left and right sides of the screen. So we can imagine 500 or so of these rubber bands lined up down the screen, each one with one line of picture information printed onto them. With Herculean effort (or should it be Xenalean effort?) we stretch these bands from their comfortable 4:3 width into 16:9. The picture distorts, the printing on the rubber bands stretch and we end up with the short fat people syndrome, aka Strech-o-vision™. But wait - what if we printed onto the rubber bands a slimmed down version of the picture, which at 4:3 made everyone look tall and skinny? Then when we stretched it out it would look correct! That, in a nutshell, is an anamorphic picture.

 

Figure 6

Anamorphic Widescreen – before it is stretched from 4:3 to 16:9, making us all look tall and thin

Technically there is no reason why the old analogue television transmissions cannot be anamorphic. But they are not - don't confuse the mild 'letterboxing' they do, especially for drama, on analogue transmissions. For completeness I should mention that letterboxing is where they effectively remove 30% of the lines by replacing them with black - those black bars at the top and bottom of the screen. So, assuming 500 visible lines of picture, you could lose about 167 of those to the black bars! Most widescreen TVs have a 'zoom' function, as I hinted at earlier, that will convert the 4:3 letterboxed picture into 16:9 by chopping the top and bottom off the picture, i.e. removing the wasted black lines. Obviously this means your picture has 30% less lines than it should have - the picture is therefore noticeably inferior. It doesn't help that most analogue letterboxed transmissions actually have much smaller black bars than that (as a compromise for older 4:3 sets), meaning when you zoom to fill the width of your 16:9 screen you are chopping off both the black bars and many good lines leading up to them.

So, there are two types of widescreen pictures - anamorphic and letterbox. With anamorphic all the lines are used and are stretched, like rubber bands, to fill the wider 16:9 aspect ratio compared to the 4:3 they are technically transmitted in. With letterbox as few as 66% of the lines are used, only those in the middle, with the top and bottom lines transmitted as bars of black - instead of stretching the lines the widescreen TV just zooms in on the middle ones until their width matches the width of the 16:9 set.

Now the astute among you will already have spotted the problem with anamorphic pictures - they are great for widescreen TVs but what happens with old 4:3 sets? These old TVs don't know anything about stretching or zooming the picture; they just transmit the 4:3 picture they receive as if it were designed as a 4:3 picture. This means that anamorphic pictures on an old 4:3 set makes everyone look tall and thin (as the previous graphic). That is why you don't get anamorphic analogue transmissions, it isn't that a digital transmission is needed because, ultimately, all television pictures are transmitted the same - 4:3. The real problem is that most old 4:3 TVs simply don't know how to handle the squashed anamorphic picture. With a digital platform you always have a decoder that converts the digital picture into the analogue picture your TV can handle. If your TV doesn’t understand anamorphic then you can tell your digital decoder and it will convert the picture to letterbox by removing every fourth line, pushing together the remaining lines into the middle of the screen and adding black bars at the top and bottom.

 

Figure 7

Anamorphic converted to Letterbox for a 4:3 TV

I hope that explains a little about how widescreen TVs work and, especially after seeing the graphics, is enough to educate those amongst us who use Stretch-o-vision™ on video designed for 4:3 aspect ratio TVs.  Set your TVs to 'Auto Aspect Ratio' and you can happily watch old 4:3, Letterboxed and Anamorphic video in the way their creators intended.  Never again will you embarrass yourself by stopping a celebrity in the street and exclaiming how much taller and thinner they appear in real life!