The big, cheap monitor roundup

Unless you fork out big, your panel - like all of the panels we reviewed - is going to use a technology called the Twisted nematic field effect (TN) to display different colours. TN panels are great because they’re cheap to manufacture and have a very rapid response time, but they fail epically when it comes to colour reproduction.

TN panels don’t display the full 16.7 million colours that they claim to be able to display. Not even close, actually. The number 16.7M comes from 256 shades (represented in 8 bits) of each of red, green and blue colour component, which when combined gives 256³, or 16.7 million shades. Current TN panels can only display 64 shades (6 bits) per colour giving us a grand total of 262,144 possible shades. While there are some true 8-bit TN panels hitting the market, they’re hardly what you’d be able to call budget.

There are others technologies that have higher image quality (Vertical Alignment, In Plane Switching), but these come with a steep price premium and generally have a slower response time. The extra expense makes these better technologies hard to justify unless you do professional image work, and as a result, nearly all the LCDs you see around today use TN technology.

The LCDs that we’ve reviewed can actually show more shades than we’ve given them credit for, but it doesn’t really have much to do with the physical panel - it’s the firmware that makes all the difference.

TN displays use an old trick known as dithering in order to display those missing hues, and there are two ways in which LCDs can dither. The more traditional (but vastly inferior) method blends colour across multiple pixels like an inkjet printer, but this tends to look ugly – it visibly distorts the image with checkerboard patterns.

Nowadays, the more dominant and visually superior method for dithering is by blending across time, known as Frame Rate Control (FRC) or temporal dithering, exploiting a phenomena with our visual system called persistence of vision. We perceive a colour somewhere in the middle of four rapidly flickering and similar hues.

Both of these methods display around 16.2M colours, still shy of the mark by some 500,000 hues, but this shortfall is a lot harder to notice and is clustered around the brightest and darkest hues. Using a combination of these methods it is possible to display the full 16.7 million colours.

A lot of the monitors we looked at had panels that were either identical or close to it, so we can see that the difference between a good and a bad monitor can come down to the firmware. The supplied specifications didn’t mean a lot in terms of performance either, so you should never buy a panel without seeing it in action first. If you want to read more about the technology behind LCDs, there are some great articles (if slightly dated) here, here and here -- as well as our own look at them here.