Just when things had settled down with full high definition resolution, the number of pixels in a consumer display is again up in the air.

Everything was going along so well. High definition standards were settled. What everyone needed in their homes was a display showing a grid of pixels: measuring 1,920 horizontally and 1,080 vertically.

But technological advancement marches relentlessly on.

Two recent TVs have tried to challenge this settled resolution. Not all that successfully, it seems, but they are pointing the way to the future.

What to do with 691,200 pixels?
Ever since the first flat panel displays appeared in the late 1990s there has been an unsteady march towards higher resolutions.

It has been unsteady because it has usually been convenient to adhere, at least to some extent, to formal or informal standards – often ones related to computer displays.

The first plasma TVs offered 640 pixels across by 480 vertically in a 4:3 format. That was suitable for American standard definition TV, but little else. Soon they went widescreen and the standard resolution was 852 by 480 pixels.

But back in their development laboratories engineers were working on making pixels smaller and screens bigger.

There is little point to boosting stuff by just a smidgeon. What purpose would a 520 pixel tall display serve? Instead, rather than a smooth progression in increasing resolution, they jumped up in significant steps, still guided at least in part by computer standards (640 by 480 is VGA and XGA required a vertical resolution of 768 pixels).

If we take a 50-inch screen as the standard, they went from 852 by 480 pixels to the next computer standard (on the vertical axis): 1,366 by 768 pixels. Home theatre front projectors rested for a while on a HD broadcast format: 1,280 by 720.

Then they paused there for a couple of years. There were variations, of course. 107cm plasmas tended to have a resolution of 1,024 by 768 rectangular pixels, and there were some models around with 1,024 by 1,024. But the next major step had to wait until the engineers accumulated enough techniques to create full high definition. Once the first models appeared, things proceeded rapidly, and now the norm is 1,920 by 1,080 pixels, both for projectors and plasmas. And, of course, for LCD TVs.

But that isn’t a natural stopping point for the technology. Why should the continuing shrinking of pixels, and the consequent packing of more of them into a display, stop? But it is a natural stopping point for the market, at least for the moment. With Blu-ray offering a maximum of 1,920 by 1,080, why bother going higher?

Still, with a physical ability to pack in more pixels, higher resolution products have started to appear, searching for uses for those extra pixels.

Perhaps the first was Philips, which last year released its Cinema 21:9 LCD display. Rather than 1,920 by 1,080, this had 2,560 by 1,080 pixels. The extra pixels altered the aspect ratio to a wider 21:9. The additional width allowed it to scale up a 2.35:1 movie to fill up the screen, eliminating black bars at the top and bottom.

Another one is Sharp – perhaps the main LCD developer in the early days – with its ‘Quattron’ models. These have a lot more pixels than a full HD display, but this raised the problem: what to do with them?

Three- or Four-Colour
Each pixel in a plasma or LCD TV, and in many projectors, actually consists of three ‘sub-pixels’. To form the range of brightness and colours required, a pixel has to produce red, green and blue colours. Separate plasma cells or sections of the LCD panel handle that.

The total pixel count of a Full HD panel is 1,920 by 1,080 pixels, which comes to 2,073,600, or 6,220,800 subpixels.

Sharp’s Quattron model increases the number of subpixels by one third. But increasing the actual pixel count didn’t really make much sense. It would result in the odd pixel count of 2,217 by 1,247 pixels. Such a display could actually degrade picture quality because of the need to scale the native video to a non-native resolution, especially one that is only slightly higher.

So what Sharp did instead was add an additional subpixel to each pixel. Instead of each pixel being created by a combination of red, green and blue, it became a combination of red, green, blue and yellow.

Four colours: thus the name ‘Quattron’.

The problem was that it offered little, if anything, in the way of actual visible improvement. There were two reasons for this. First, yellow is an area where the standard three colour model already does a pretty good job… indeed, the best job. There is more room for improvement in purples than yellows.

Second, what’s to improve? Blu-ray and DVD and digital TV all use the standard RGB model to carry their picture information. There isn’t any additional or unexpected yellow in the signal to worry about.

Those engineers would do better to hoard extra subpixels for the time being. When the engineers have got the pixel density (for a reasonable price) up to the point where 4K displays (3,840 pixels across, or more) can be delivered, then they’ll be worthwhile. Not for extra colours, but for extra pixels for smoothing diagonals and removing the last residual jaggies from full high definition displays.

Reducing the pixel count through three dimensions
Korean electronics giant LG, on the other hand, has gone the other way and halved the resolution of its TVs.

Not all the time, I must hasten to add. But it has done so for 3D content.

Most 3D TVs use a system of shutter glasses. The left and right eye images flash up on the screen in sequence, and the liquid crystal lens in the glasses of the viewers flash transparency on and off in time with this.

Many people find this flashing or flicker disturbing and have to stop watching. LG’s new range of ‘Cinema 3D’ TVs use a very different system. Each pixel in the display is polarised, restricting light waves with either a left twist or a right one.  Matching polarised glasses ensure that only the appropriately twisted light is passed through to the viewer’s eyes.

There is no flashing, but it means that your left eye can only see half the pixels, and your right eye can only see the other half the pixels.

It seems to work very nicely for the 3D effect, and really does ensure that there is no flicker (which is largely subliminal, but still seems welcome by its absence). In addition, the polarised eyewear worn by the user is entirely passive, and is consequently very low in cost (a few dollars instead of the hundred-dollar-plus amounts).

Nonetheless, the loss of resolution is clearly visible as diagonals display jaggies which can be easily seen by the eye at a reasonable viewing distance. It is each horizontal row of pixels that is polarised the opposite way to the one above and the one below it.

A Clear Reason for More Pixels

There are two obvious solutions to this. One is the Samsung option. It was recently announced that it had entered into an agreement with RealD 3D for developing a polarising system of its own. But this system will use active polarisation, flashing the left and right twist polarisation over the top of the picture in time with the flashing of the left and right frames.

This ought to work, since it is effectively what is used in most cinemas. But it potentially reintroduces flicker.

The flicker-free, jaggie-free way would be to increase the TV’s resolution to something like a 4K TV. In fact, you could achieve full 3D resolution simply by doubling the vertical pixel count, while making no changes to the horizontal one.

Such TVs would show 1,920 pixels by 2,080. With non-3D material, each pair of vertically adjacent pixels could show the same thing, or the TV could interpolate new pixels, according to the designs’ capabilities.

And this increase in pixels isn’t actually all that much more than Sharp has added for its Quattron models.

So perhaps there is room for a continuing incremental increase in picture resolution.