A decent LCD screen is the best PC investment you can make

8th May 2010 | 09:00

A decent LCD screen is the best PC investment you can make

But don't be misled by misleading specs

Rack up a few years in tech journalism and it's all too easy to become blasé. Would sir care for a new six-core processor? Perhaps an expensive SSD would suit sir better? Very well, if you must.

However, casual but comprehensive access to the best kit also makes it abundantly clear just how much impact any upgrade has on the end-user experience. Despite my proven predilection for slices of silicon, it's not graphics chips, SSDs or even CPUs that top the tables.

Instead, a decent LCD display is the single best and longest lasting investment you can make for your PC. There's nothing else as transformative to your day-to-day computing pleasure.

As ever, there is a catch. LCD panels are blighted by baloney. By that I mean that the official specifications quoted by monitor manufacturers are often misleading at best. That's partly because you get far more variance from one supposedly identical LCD panel to the next than you do, for instance, with two CPUs.

But I reckon it's also because monitor makers know that punters don't have the expertise or equipment to keep them honest. How is your average Joe supposed to confirm his pricey new panel delivers on its alleged 1,000:1 contrast ratio?

Frankly, he can't. By contrast – no pun intended – it's trivial to check whether a CPU really hits its claimed clockspeed or if one graphics card cranks out more frames per second than another.

Despite all that, a few simple factoids will put you en route to something approaching flat panel perfection.

Firstly, forget contrast ratios, viewing angles and claimed colour depth. It's all about the panel type. There are three key LCD panel technologies: TN, IPS and PVA.

TN is cheapest and nastiest. Nippy pixel response aside, it falls short of the other two by every image quality metric.

IPS is usually the choice of graphics professionals thanks to its superior colour accuracy, while PVA offers the deepest blacks and most vibrant images, making it a good choice for general use.

The key point is that panel type trumps any other specification. The latest TN panels, for instance, are claimed to achieve the same 1,000:1 static contrast as a good PVA monitor. And yet there's no doubting that, subjectively, blacks look much better on a PVA panel.

A further weakness of TN tech is colour depth. Truth is, TN panels are only capable of 6 bits per colour channel. That works out at around 250,000 colours, compared to the minimum 16 million delivered by PVA and IPS.

To compensate, most TN monitors use a trick called dithering. This involves approximating an intermediate colour by rapidly jumping between two adjacent colours. If that seems like a kludge, it is. Indeed, look closely at some TN panels and you can see the pixels fizzing away as they hop between colour states. Apparently, this is good enough for nearly all makers of TN monitors to claim 16 million colour capability. Shocking.

Next, beware fancy-sounding image enhancement technologies. The most common are pixel overdrive and dynamic contrast. The first is designed to improve the responsiveness of LCD panels by pumping elevated voltages into the pixels. While often effective, it can be problematic. If used too aggressively, it can generate a visual artifact known as inverse ghosting, which takes the form of a dark trail behind moving objects.

Ironically, overdrive can also introduce a noticeable delay between the output from the graphics card and the image displayed. Known as input lag, it's typically noticed as laggy response to mouse inputs. At it's worst it can make your PC feel infuriatingly sluggish.

As for dynamic contrast, that's a ruse that adjusts the backlight intensity on the fly to suit the brightness of the image being rendered. It sounds like a good idea in theory, but thanks to the laggardly response of the CCFL backlights found in the vast majority of monitors, it doesn't work well in practice. In fact, it's so ineffectual I suspect the only reason it exists is because it's cheap to implement and allows manufacturers to fluff up their figures.

Disgracefully, some manufacturers are not always explicit about whether dynamic technology is responsible for their quoted contrast performance. But it's pretty easy to tell. Anything over 1,000:1 and certainly anything over 3,000:1 will very likely be courtesy of dynamic contrast.

Finally, remember that, to date, any monitor claiming to be 'LED-powered' is just a conventional LCD display with a big, dumb LED backlight. Local dimming, as seen in HDTVs, has yet to arrive in PC monitors – so don't say I didn't warn you.

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First published in PC Plus Issue 294

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