The price of TFT (LCD) monitors has fallen dramatically over the last two years and its now possible to buy large screen, 20+, for the same price as a traditional CRT.
The technology is improving too, even at the cheaper end, which is what this guide is really about but the best CRTs are still better than TFTs in some ways.
TFT have a fixed number of pixels on the screen and what is called a native resolution and you cant adjust it without compromising overall performance. Also they arent as good at displaying colour/contrast as a decent CRT and response time (see below) can mean that games can appear smeary at higher frame rates.
But all these things are improving, they use a lot less power, produce minimal radiation are far lighter, so can be moved around easily and dont suffer from the distortion caused by the curve of a CRT tube. And you can get a good size widescreen at reasonable price too, great if you want to display two documents or webpages side by side.
Specifications
Resolution
Response time
The time a pixel takes to switch on and off, measured in milliseconds (ms). These used to be quite high but have fallen dramatically recently. The commonest speed is 5ms but if you play games look for something between 3 and 4 or movement will appear blurred or smeared.
Contrast
One of the problems with TFTs is how they have handled contrast, the difference between the darkest and brightest part of the image but this has improved recently, however its one of the more deceptive aspects of specifications. Its expressed as a ratio, 300:1 etc and the higher the first number the better according to "blurb" but the most important thing is how the monitor handles gradations in tone. You want high contrast but you'll need to read reviews to see how well a monitor handles the subtle tones at the extremes.
Modern TFTs will have ratios of 500:1 to 1000:1 but some will claim up to 3000:1. The higher ratio is often achieved by various enhancement systems and youll need to check reviews to find how effective it is, the manufacturers site should list what it is by standard measurement.
Brightness
Almost all monitors quote a figure of 300 cd/m², which is really bright, most reviews I read reported that brightness had to be turned down for comfortable viewing. As luminance is measured in terms of the number of candles in a square meter, you can see why.
Colour
Most TFT claim 16.7 million colours which is the truecolor standard but some achieve this dithering (flickering) individual colours. Look for screens with 24 bit colour.
Viewing angle
Monitors can look great from right in front but can loose colour, contrast etc the further you look at them from the side or above. It only really matters if you want to share the image, in which case the higher the figure in degrees the better. The monitor I bought boasted 170/160 degree horizontal/vertical viewing angles, it's certainly acceptable at that, you can make out what is on the screen but to see colours and contrast properly you need toview it head on and just shifting your head slightly to one side makes a difference.
Connections
As a TFT is true digital display, it makes sense that it should have a digital interface, yet some dont. Make sure the one you get does, lack of one degrades the image. The main types of connections are:
Screen type
This isnt very prominently displayed in the specifications and you may have to go to the manufacturers website to find out which a particular monitor has. If youre buying at the cheaper end of the market its going to be a TN+film, here the basics of the three most common types:
Dead Pixels
Another thing that isnt mentioned in specifications except as a compliance standard that few people understand, to make things more complicated, it also refers to three (red, green, blue) sub-pixels that each individual pixel is made up of. And dead doesnt just mean dead, it can mean always on too. Because of the delicacy of the manufacturing process it is very difficult to guarantee that every single one of the pixels will be functioning properly without throwing an enormous number of otherwise perfect screens away, so makers have agreed standards that allow for a limited number of dead pixels per million pixels.
The agreed standard is called ISO 13406-2 (click here), it specifies the number dead, always on and sub pixels there can be per million pixels. Monitors are divided up into to four classes and most are sold today are class two which specifies 2, 2 and 5 faulty pixels per million.
Some manufacturers have their own standards by which they grade their screens, as do the sellers, so its well worth checking what these are as failure to understand dead pixel policies is one of the commonest cause of complaint regarding screens.
Its also a good reason for not buying one through eBay as many of the monitors that appear on the market will do so because theyve been returned due to have a lot of dead pixels.
The above is a summary of what I learnt while looking for a new monitor, any corrections or further points worth mentioning gratefully received!
The technology is improving too, even at the cheaper end, which is what this guide is really about but the best CRTs are still better than TFTs in some ways.
TFT have a fixed number of pixels on the screen and what is called a native resolution and you cant adjust it without compromising overall performance. Also they arent as good at displaying colour/contrast as a decent CRT and response time (see below) can mean that games can appear smeary at higher frame rates.
But all these things are improving, they use a lot less power, produce minimal radiation are far lighter, so can be moved around easily and dont suffer from the distortion caused by the curve of a CRT tube. And you can get a good size widescreen at reasonable price too, great if you want to display two documents or webpages side by side.
Specifications
Resolution
- Number of pixels on the screen, unlike a CRT these are actually the number of pixels. Its worth noting that two of the most common sizes 20 and 22 widescreens often have the same number, typically 1680X1050, so the screen might be physically bigger but showing the same image.
- Frequency, expressed as Hertz (Hz), is the screen refreshes the image each second. Anything less than 70hz is seen by the eye as flicker, so the higher the better.
- Dot pitch is the gap between pixels, look for a figure under 0.299.
Response time
The time a pixel takes to switch on and off, measured in milliseconds (ms). These used to be quite high but have fallen dramatically recently. The commonest speed is 5ms but if you play games look for something between 3 and 4 or movement will appear blurred or smeared.
Contrast
One of the problems with TFTs is how they have handled contrast, the difference between the darkest and brightest part of the image but this has improved recently, however its one of the more deceptive aspects of specifications. Its expressed as a ratio, 300:1 etc and the higher the first number the better according to "blurb" but the most important thing is how the monitor handles gradations in tone. You want high contrast but you'll need to read reviews to see how well a monitor handles the subtle tones at the extremes.
Modern TFTs will have ratios of 500:1 to 1000:1 but some will claim up to 3000:1. The higher ratio is often achieved by various enhancement systems and youll need to check reviews to find how effective it is, the manufacturers site should list what it is by standard measurement.
Brightness
Almost all monitors quote a figure of 300 cd/m², which is really bright, most reviews I read reported that brightness had to be turned down for comfortable viewing. As luminance is measured in terms of the number of candles in a square meter, you can see why.
Colour
Most TFT claim 16.7 million colours which is the truecolor standard but some achieve this dithering (flickering) individual colours. Look for screens with 24 bit colour.
Viewing angle
Monitors can look great from right in front but can loose colour, contrast etc the further you look at them from the side or above. It only really matters if you want to share the image, in which case the higher the figure in degrees the better. The monitor I bought boasted 170/160 degree horizontal/vertical viewing angles, it's certainly acceptable at that, you can make out what is on the screen but to see colours and contrast properly you need toview it head on and just shifting your head slightly to one side makes a difference.
Connections
As a TFT is true digital display, it makes sense that it should have a digital interface, yet some dont. Make sure the one you get does, lack of one degrades the image. The main types of connections are:
- VGA old analogue connection.
- DVI-A Analogue only.
- D-sub Analogue only.
- DVI-D Digital only, make sure your graphics card has a suitable connector.
- DVI-I Digital and analogue accepted.
- HDMI Digital only, unusual on PC monitors, mostly used for TV.
Screen type
This isnt very prominently displayed in the specifications and you may have to go to the manufacturers website to find out which a particular monitor has. If youre buying at the cheaper end of the market its going to be a TN+film, here the basics of the three most common types:
- TN+Film is the oldest type of display and commonest in the consumer market. Early models (cheap on eBay) were TN only and had very bad viewing angles, the addition of a film layer has alleviated this to some extent. They also only used 6 bit technology to produce colours which meant that they couldnt display the full 16.7million colours (24bit RGB) without dithering (adjusting pixels between shades), newer models can display the full palette. They also suffer from slight bleeding from the back light around the edge of the screen but this should only be noticeable when the screen is totally model (check reviews though). Very good response times.
- IPS was developed to improve colour and viewing angle, they have true 8 bit colour, less backlight bleed and fewer screen artefacts. The are several versions of the technology depending on manufacturer and are generally the most expensive on the market.
- MVA is a compromise between TN and IPS, better colour and viewing angles than the former, better response time than the latter.
- Read here and here.
Dead Pixels
Another thing that isnt mentioned in specifications except as a compliance standard that few people understand, to make things more complicated, it also refers to three (red, green, blue) sub-pixels that each individual pixel is made up of. And dead doesnt just mean dead, it can mean always on too. Because of the delicacy of the manufacturing process it is very difficult to guarantee that every single one of the pixels will be functioning properly without throwing an enormous number of otherwise perfect screens away, so makers have agreed standards that allow for a limited number of dead pixels per million pixels.
The agreed standard is called ISO 13406-2 (click here), it specifies the number dead, always on and sub pixels there can be per million pixels. Monitors are divided up into to four classes and most are sold today are class two which specifies 2, 2 and 5 faulty pixels per million.
Some manufacturers have their own standards by which they grade their screens, as do the sellers, so its well worth checking what these are as failure to understand dead pixel policies is one of the commonest cause of complaint regarding screens.
Its also a good reason for not buying one through eBay as many of the monitors that appear on the market will do so because theyve been returned due to have a lot of dead pixels.
The above is a summary of what I learnt while looking for a new monitor, any corrections or further points worth mentioning gratefully received!
