Choosing a display can be a confusing process, bombarded as you are with numbers and information from all the manufacturers’ and vendors’ websites so here we will try and de-mystify all the facts and figures that get quoted in display specifications and try to help you decide what type of display is best for you. Any good reseller (like us) would be more than happy to guide you through the process over the phone.
Before we start discussing the nitty gritty it’s worth pointing out a few general principles. When looking for a monitor there are various ways you can filter the large numbers of models and manufacturers on the market. The most obvious is deciding what your budget is, the next most obvious is perhaps the size of screen that you need. One factor that most customers don’t consider is perhaps what the screen is designed for. Most screens are designed for general home or office use. To be good for colour critical applications monitors have to have higher quality standards and a few special features. It’s a bit like buying a car. You could start looking for cars based on fuel consumption or 0-60 times but those raw figures wouldn’t account for factors such as transporting several kids or the fact that most of your driving might be on the motorway, or the fact that you might want the reassurance of a quality brand. If you factor in qualitative and functional differences rather than just the raw performance figures you’ll choose a very different car. It sounds obvious but many customers don’t approach buying a monitor that way.
For instance whenever we get asked by a photographer about what level of monitor they should aim for we always ask them about their approach to the quality of their camera gear. If they are the type who always buy Nikon or Canon high quality lenses we say to them they should probably aim for the best in monitors as well as otherwise their monitor could be the weak link in the chain that means they don’t see the benefit of the good lenses. Likewise if they do compromise for budgetary reasons on the quality of the lenses then a cheaper monitor might be best for them.
The best advice we can give is to look at the specifications and marketing text listed by monitor manufacturers and then have a good look around the internet for reviews, but make sure the reviewers are in the same business as you otherwise they may be praising or critiquing a monitor for features or functions you won’t use whilst perhaps ignoring things like colour accuracy and uniformity.
Older CRT and LCD screens generally had the aspect ratio 4:3, like older TVs. Now screens are usually 16:10 or 16:9 and referred to as Widescreen, you can even get some ultra wide ones that are 21:9. Some customers think that a widescreen monitor will stretch their image like the first widescreen TVs did to old 4:3 format programs. This isn’t the case. As long as the correct resolution is set (usually automatically) in the graphics card images won’t appear stretched on widescreen monitors. What you will get though is more room for your palettes etc. In applications such as Photoshop. The screenshots show the same standard 4:3 digital photo displayed on a 16:10 and 4:3 screen. Notice that you can’t see the whole image on the 4:3 format monitor because of the space taken by the palettes.
Display brightness is measured in cd/m2 (candelas per square meter). Most displays can theoretically display levels as high as 400 cd/m2 but at such levels the back light would age prematurely and look far too bright. When you calibrate a display you will usually aim for a brightness level of around 80-120 cd/m2 depending on your ambient lighting and print viewing conditions so maximum brightness isn’t that important.
The contrast ratio of a display is simply the relationship of the brightest white to the darkest black pixels the display can output. Manufacturers frequently quote figures of 1000:1 or more, based on running the display at maximum brightness (see above), however these figures are pretty meaningless because once you calibrate the display you will typically be achieving a contrast ratio of around 400-500:1 and this is plenty for colour accurate viewing.
Every display has a range of colour it can reproduce. This is called its colour gamut. Manufacturers compare the colour gamut of their displays to other industry standards and gamuts. NTSC is a TV standard and widely used as yard-stick for display gamuts but outside of the TV industry it doesn’t really mean very much. Adobe RGB (1998) is a colour gamut used widely in photography and ISO Coated v2 is a colour gamut used in printing. Good colour accurate screens are now showing around 98% of Adobe RGB or higher and 99% of ISO Coated v2 or higher. The problem is that there are different ways colour gamuts can be compared. The best way is to compare how the display gamut covers the target gamut and not simply compare the raw size of the two gamuts. Colour gamuts are sometimes irregular shapes so just comparing the gamut volumes might not tell you much. However, gamut volume comparisons give higher sounding numbers rather than the more accurate gamut coverage comparisons. To further complicate things you can actually vary the mathematical models used to skew the numbers in your favour, something that some manufacturers’ marketing departments are known to do! Generally only RGB LED backlit screens will achieve 100% or more of Adobe RGB. Users who intend to use their monitors for office work or web browsing do not need wider colour gamut monitors, but if you are a photographer using the Adobe RGB working space or Adobe Lightroom then you will see your images more accurately on a display that more closely matches or even exceeds the Adobe RGB gamut. Similarly if you are working in pre-press then your display should cover the ISO Coated gamut for accurate soft-proofing.
The green line is a representation of the Adobe RGB colour space, and the yellow is sRGB. The red line is the colour space of a particular EIZO ColorEdge monitor and you can see in some areas it exceeds Adobe RGB and in some it’s a bit smaller. The blue line is one of the EIZO Flexscan models and you can see it’s far closer in gamut to sRGB.
Most display calibration software works via adjustments to the graphics card look up tables and/or by getting the user to manually adjust the settings of the display. However, displays designed for colour accurate work come with their own calibration software that communicates with the display’s own internal high bit look up tables and also adjust backlight levels etc. and so produce a more accurate calibration more easily. With software based monitor calibration the adjustments needed to get the monitor displaying the correct colour are either done in the graphics card which usually has simple 8 bit tables for each colour, or the correction is done in the monitor controls manually. In either case corrections may necessarily lessen the amount of RGB values in each colour. Whereas hardware calibration that takes place in high bit look up tables within the monitor does not reduce the RGB values that are output resulting in the preservation of more detail on screen.
In the above simplified example the screen image is too magenta and so a software based calibration system might have to limit the red and blue channels to get the correct colour. This would result in an output range of 0-240 for red and 0-235 for green. If the same adjustment is done within the monitor look up tables by hardware calibration 0-255 is still output for each colour.
Most monitors designed for colour critical viewing come with hoods to limit reflections on screen. Such hoods are also available for other monitors at reasonable cost but the fact that a monitor comes with an hood is a good indication it’s designed for colour accuracy.
Displays need to be connected to the computer graphics card. DVI was the most common cable connector used but Display Port connector is becoming more widely used and has the advantage of supporting 10-bit display – see section below. HDMI is also common on many monitors. Apple Macintosh computers come with Thunderbolt ports. Mini Display Port cables are compatible with Thunderbolt. Many of our monitors come with a Mini Display Port cable and we always try and list what cables each models come with but if in doubt give us a call. We do sell a Mini Display Port cable if you need to buy one.
Look Up Table
Monitors process the signal from the computer though a look up table (LUT). The higher the number of digits or bits those look up tables can use the smoother the gradations of colour on your display. The best colour accurate displays will have 14 or 16-Bit LUTs to enable very smooth colours and greys. Some displays have LUTs that work in 3D (one dimension each for Red, Green and Blue) allowing even better mixing of colours.
TFT or LCD panels are made up of grids of tiny pixels. The terms TFT and LCD are both used to describe the technology now used for computer displays and TVs. Each display has a native resolution that it should be used at, for example 1920 x 1200 pixels. Generally speaking, the bigger the display, the higher the native resolution. You can run a display at a resolution less than its native one but the image will tend to look blurred as information is getting spread over a larger number of pixels. If you want larger type on a display increase the display type size in your operating system or application’s preferences.
You may have heard of 4K as an emerging standard in cinema and TV but 4K computer monitors are now being released. 4K refers to the number of horizontal pixels True 4K displays are 4096 pixels across and UHD (Ultra High Definition) displays are 3840 across. 4K/UHD screens offer very sharp pictures but you do need the right graphics card to drive them. As well as the resolution you should make sure that your graphics card can drive the screen at a sufficiently high refresh rate. Driving such a high definition screen takes a lot of bandwidth. Some cards will drive a 4K/UHD screen but only at 30 or 24 hertz and this can make your computer sluggish as most monitors are used at 60 hertz. HDMI is currently limited to 30 hertz with 4K screens because it doesn’t have the bandwidth. Display Port can drive a 4K screen at 60 hertz but you still need to check that your particular graphics card is able to. You will also need to use display scaling on your operating system to make the interface text big enough to read. Call us if you need advice on 4K or UHD monitors. See our range of 4K screens here.
There are three types of TFT panels. TN, VA and IPS, each acronym refers to the method used to make the display. You’ll often find various prefix letters in front as well. TN (Twisted Nematics) is the cheapest of the three technologies and generally produces the poorest viewing angles and the smallest colour gamuts – we don’t tend to sell TN panels. Cheap displays and most laptops use TN panels. They should not be used for colour critical purposes. VA (Vertical Alignment) screens are better and have reasonable viewing angles but with perhaps some colour shift at the extremes. IPS (In Plane Switching) have the best viewing angles and are generally used in the highest quality displays. All of the screens we sell are IPS.
It takes a certain amount of time for pixels on a TFT panel to change colour. When working with still images this isn’t really an issue but it can be with video. Early TFT displays had long response times. Almost all modern displays now have response times below 10ms (milliseconds). Response times quoted by manufacturers don’t really tell the whole story as the way the tests are done are quite artificial but generally any modern LCD display will handle video or games well enough for most users.
Uniformity and Stability
Other key features to look out for if you need a colour critical display are features that ensure uniformity across the screen and stability over time. The names and acronyms used to describe these features vary from manufacturer to manufacturer but generally do similar jobs.
All LCD screens have some problems showing uniform colour across the screen. Displays designed for colour accuracy will generally be measured in the factory and any uniformity problems corrected in the internal software by editing the output signal to compensate for any variation in lightness or colour. Many high quality screens also come with some form of uniformity guarantee.
As an LCDs backlight warms up it can change in brightness so some monitors have sensors that monitor and adjust the back light to ensure consistency as it warms up and also over longer periods of time.
The above image shows data measured from a monitor with (left) and without (right) uniformity compensation. The red and orange areas are the areas of highest colour difference from the centre.
TFT displays can sometimes show different colours depending on the relative angle of your eyes to the plane of the display. Manufacturers often quote values close to 180˚ implying that you should see very little colour or brightness shift at all but those figures don’t tell you everything as there will still be some tolerance of difference allowed within the specification of the display. Viewing angles are only really a big concern for displays larger than 24 inches or if you regularly work with people looking at the display from over your shoulder etc.
Whilst we hope any monitor we sell doesn’t go wrong obviously some do and if you aim to have the monitor for a long time or use it for business critical purposes then the length, coverage and terms of any warranty are important considerations. Most of the top of the range monitors come with some form of advance replacement meaning if your monitor goes wrong then you get a replacement loan monitor before yours is taken away. Cheaper monitor obviously might not have this kind of cover.
Currently the software in your operating system and your graphics cards process colours in 8-bit allowing 16.7 million colours to be displayed. Display Port connectors allow for 10-bit data to be output to your monitor and many displays are now ready to process that data in 10-bit, allowing over one billion colours to be displayed. However the whole chain from application to monitor must be 10-bit enabled. The Mac OS does not currently allow 10-bit but with a Windows PC, a compatible graphics card and many recent applications such as Photoshop CS5 or later you can get 10-bit display. See our blog article for more details.
[box type=”note”]There are other features you can look for as well, depending on your needs. Some displays have USB hubs built-in. Many quote external standard agencies such as UGRA, FOGRA and SWOP. These are all printing organizations or standards agencies that have certified or tested the display. As with most things in life, generally you get what you pay for.[/box]
- Colour Critical Monitors (including EIZO ColorEdge and NEC SpectraView)
- Creative Monitors (ideal for amateur photographers and designers)
- 4K Monitors (for those wanting the highest resolutions)
- General Monitors (including home and office)
- Monitor accessories (including cables, hoods and stands)
- Monitor Profiling