Choosing a new monitor

11 February 2009

LCD monitors have advanced greatly in recent years and capabilities vary from model to model. But choosing your new screen by comparing specifications like for like is easier said than done writes Rob Jamieson

Designers spend a considerable amount of the day trying to pick details out on a monitor. LCDs are the most common screens in use and can start at a very low price - as low as £59 - but are they any good for long term use? You’re only given one set of eyes for your life, so do you really want to take a chance?
So what are the different types of screens available? There are three major technologies TN (Twisted Nematic), IPS (In Plane Switching) and VA (Vertical Alignment). Each have their advantages of image quality, refresh rates and cost.

At the entry-level are the TN screens which are cheapest to manufacture. They are found in most of the new netbooks or cheaper desktop displays. They work by twisting the molecules of liquid crystal when voltage is applied to block the backlight and therefore create an image. The blocking of light makes these less bright than other types and they have a reduced contrast. They also have restricted viewing angles but the twisting is very fast giving them good response times. This is useful in CAD as we hate to see “blur” when we rotate models.

IPS screens have multiple controllers per picture cell giving greater accuracy and more control over colours. Better angled alignment of the liquid crystals in IPS screens gives increased viewing angles. IPS screens are not as fast as those based on TN technology but the better quality ones are not so far behind. They are harder to make so are more expensive.

VA screens have two sub types called Pattern and multi-domain, but Pattern is more common. In technology terms VA is a mix of TN and IPS but as the default position of the liquid crystal is to block the backlight VA screens have the best quality blacks.

Backlights provide the white light that the liquid crystal then manipulates to create the image. LED backlights are the new kids on the block and provide a brighter stronger light. They also last longer. There are a few monitors available like the HP DreamColour LP2480zx that use LED backlights combined with a quality IPS screen to give ultra colour gradients and 10-bit colour support. Other manufacturers are starting to offer LED backlights and are combining them with all the different options above to tailor for different markets. By using LED backlights with VA or LC, such as Samsung is doing in the domestic TV area, LCD screens are finally starting to rival CRTs of old in terms of colour depth and smooth graduations.

LCDs can start at a very low price but are they any good for long term use? You’re only given one set of eyes for your life, so do you really want to take a chance?

For CAD, of course, resolution and size are important. A few years back I was an advocate for multiple monitors for CAD but today I prefer just a large single screen, 22 inches or above. If you are getting short sighted (we all do I’m told, as we get older) then a resolution of 1,680 x 1,050 on a 22 inch will give bigger text and menus. If you are not feeling the onset of accelerated decrepitude get a 1,920 x 1,200 version of a 22, 24 or 26 inch screen. Finally, if you have the desk space then one of the 30 inch dual link / Display Port monitors, with resolution of 2,560 x 1,600 is great for multiple windows. You need a reasonable graphics card to support 3D at these resolutions and 3D, of course.

Monitors also come in different bit depths as well. 6-bit depth (32,000 colours) is still available on the ultra cheap monitors and perhaps some netbooks. Higher colour depths will look dithered on these screens. 8-bit (16 million colours) is the most common in modern screens with 10-bit (billions of colours) appearing now in HP’s DreamColour, for example.

The big problem with buying monitors is that there are no universal specifications. Each manufacturer quotes certain measurements but often they are not all to the same standard. Refresh rates can be measured grey to grey or on/off black to black etc. Something like 6ms is a good average for grey to grey. Viewing angle is quoted in degrees but it’s often unclear whether that’s to see good colours or sharp text. This should always be quoted for vertical and horizontal. 170 degrees is good.

Contrast ratio is another often quoted measurement, a typical example being 1000:1. In reality there are dynamic and static methods with ANSI having some tests based on reflected light.
Unfortunately some monitors still ship with ‘dead’ pixels, though this varies from manufacturer to manufacturer. The accepted standard is up to 3%, but that’s no good if it’s in the middle of your new screen. Some manufacturers offer a return process, so it’s definitely worth checking before you part with your hard earned cash.

The thing is today we tend to buy things based on reviews (I hate most user reviews because if you have purchased a product you are unlikely to say it is rubbish) or on basic specifications that do not use comparable measurement methods.

Most manufacturers don’t even give details on what type of panels they use but have vast ranges and prices. Graphics cards, CPUs and hard disks have defined specifications and a good amount of benchmarks. I understand it’s hard for competing manufacturers to come to agreements but users today are an informed audience and giving us more standardised details would help us make better choices for what we need.

Of course, buying a monitor is all about personal experience so the best way to choose a new screen is to compare them side by side using your own data, running your main 3D application or photo imaging tools. The big challenge is finding somewhere where you can do this.

Rob Jamieson is marketing manager for workstation graphics at AMD. While he may have the odd grey hair, he’s proud that he can still run his 22 inch monitor at 1,920 x 1,200 resolution. The opinions expressed in this article are not those of AMD.
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