CRT

CRT or Cathode Ray Tube monitors are the monitors everyone will have seen before. They that look like televisions. They range in size from 15 to around 22 Inch, and weight up to 30 kilos.

Advantages

Great value for money

Mature technology

Good for graphical detail

Can accommodate many different resolutions

Disadvantages

Big

Take up a lot of space

Cost more to run than an LCD

LCD/TFT

LCD or Liquid Crystal Display screens have now been around a few years, these are the thin screens. Some look almost like a picture frame. You will see them referred to as LCD or TFT (TFT being a type of LCD). They start at around 14 inches, and due to technological advances bigger LCDs are being produced all the time, 30 Inch are already available with 40 inch on the way too. They weigh very little compared to their CRT equivalent and can be mounted on a wall or shelf with ease.

Advantages

Less desk space needed

Require less power to run, more environmentally friendly

Increased Viewable area, a 15″LCD can give the same viewable area as a 17″ CRT monitor

Disadvantages

Viewing angle can affect image quality

One native resolution

More expensive than a CRT

General Monitor Features

Size

Here is one area where size does matter, the bigger the monitor the easier it will be on the eye. You will be able to open more windows and the text should be easier to read. Keep in mind the viewable area, all CRT have a smaller viewable area than their size. For Example a typical 17″ CRT will have a viewable area of around 15.8″. LCD tends to have the same viewable area, so a 15″ LCD will have a 15″ viewable area. Monitor size (and TVs) are measured diagonally, from the top left corner to the bottom right hand corner.

Resolution

Resolution is the number of pixels displayed on screen at one time, it’s usually in the format Horizontal x Vertical, e.g.?- 800×600 or 1024×768. CRT monitors can display multiple resolutions easily, while LCD monitors are optimised for 1 native resolution (They can display other resolutions, but are optimised for 1) the higher the resolution the more you can get on screen and the sharper the image.

CRT Specific Features

Dot Pitch

Dot pitch is the distance in millimetres between two dots of the same colour on the screen, it’s usually measured diagonally and you should be looking for something around 0.26mm

Refresh Rate

This is the number of time the screen is redrawn per second, most new monitors should have reasonable refresh rates, 75Hz or higher. Some older CRTs had lower refresh rates that can cause screen flicker and induce eye strain.

LCD Specific Features

Brightness

Because LCDs require their own back light to create colour, brightness is an important factor. It’s measured in candelas per metre squared or cd/m2, where one candle produces a brightness of 1 candela. The higher this number, the brighter the screen.

Contrast Ratio

This is the degree of difference between the extremes of light and dark colours. The higher the contrast ratio, the more detailed the image will be. Blacks will be blacker, whites will be whiter, and particularly text on the image will be more vivid. It will usually be written as 500:1 or 250:1

Response Time

Refers to just how quickly a pixel can change colour. It’s measured in milliseconds with 20-30ms being the normal at the moment. Gamers and people who watch a lot of movies on LCD screens would be better opting for something with a fast response time, around 16ms as this reduces the ghosting effect of fast motion.

When looking to buy a new monitor all of the above needs to be considered. Keep in mind you will be looking at your purchase day in day out for the next few years, so do not cut corners here, buy the best you can afford, your eyes will thank you for it later.

Dead Pixel Policy

Due to the difficulties associated with producing LCD screens very few brands guarantee a pixel perfect (Class 1) product,

and those that do charge a premium for it.

Most of the screens we sell currently adhere to the international standard, ISO 13406-2 and use class 2 panels.

It is possible, although uncommon, for a Class 2 LCD screen to have a small number of faulty pixels.

In these cases, this standard deems the screen as being ‘not faulty’.

For an LCD monitor to be considered faulty there has to be a certain number of dead pixels:

Acceptable malfunctioning pixels by class & type per Million pixels:

2 complete pixels constantly illuminated (a white spot)

2 complete pixels not illuminated (a black spot)

5 sub pixels constantly on or off or intermittent fault. May blink or show a pixel as a base colour (Red, Blue, Green, Cyan, Magenta or yellow)

or, any 2 sub pixel faults within a 5 x 5 block of pixels

Also, the faults are cumulative, so if you have 1 white spot and 1 black spot per million pixels then this counts.

Native Resolution Pixel Count Example

1024 x 768 786,432 2 or more dead pixels considered faulty

1280 x 1024 1,310,720 3 or more dead pixels considered faulty

1600 x 1200 1,920,000 3 or more dead pixels considered faulty

So, You can have a 19″ LCD monitor with a low native resolution where 2 pixels would be considered faulty, but if it had a native resolution of 1600 x 1200 and therefore had many more pixels, then 2 would not be classed as faulty.

For any LCD to be classed as faulty it must meet the above requirements, primarily those of the specific manufacturer. Please contact the manufacturer directly for their current dead pixel policy.

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