Jargon busted – explanation of the specifications of monitors for photography

Posted by: admin on November 22, 2011 Under: Info |

Now we’ve got an idea about the technologies behind the screens, let’s have a look at some qualities of monitors and how they‘re relevant to working with photographs and graphics.

Colour Gamut

Put simply, the colour gamut of a monitor is the range of colours it is capable of displaying. A good monitor will have a wide colour gamut, often measured against the Adobe RGB spectrum. Ideally, a monitor for photography will cover at least the sRGB spectrum and further if possible.

A monitor with a wide colour gamut will reproduce greener greens and redder reds, for example. This is often referred to as colour saturation and is obviously a good thing in a monitor for photography.

The graph below shows how colour gamuts are generally represented.

Colour Depth

Having a wide colour gamut alone is not sufficient to make a monitor good for photography. Colour gamut tells you nothing about the amount of colours a monitor can display. The number of colours is generally referred to as the colour depth.

It’s theoretically possible to have a very wide colour gamut but only a small colour depth. This would mean the monitor could display a few very saturated colours but there would be few, if any, intermediate colours between them.

A good colour depth will result in smoother transitions between colours and less banding on the screen. It will also allow colours to be displayed more accurately, qualities of monitors coveted by photographers.

Colour depth often represented by a number of bits; the higher the number of bits the more colours the monitor is capable of displaying. Twisted Nematic (TN) displays are able to produce 6-bit colour, or 18-bit colour depth (6 pixels of green, 6 pixels of blue and 6 pixels of red equals 18 bits). These monitors can produce 262, 144 colours. TN displays use a colour simulation technique known as dithering to increase the perceived number of colours.

If you’re after a good monitor for photography you want more colours available to you than this and a monitor that doesn’t use dithering. IPS and PVA panels are capable for producing 8-bit colour (24-bit colour depth) and can display 16.7million colours. This is known as “true colour” and is the minimum colour depth you should look for in a monitor for photographic use.

Modern IPS and PVA panels can even produce 10-bit colour (30-bit colour depth) allowing the monitor to display over a billion colours. However, in order to display the full colour depth the software and hardware must be compatible with 10-bit colour.

Colour Calibration

Colour calibration is an essential element of getting your monitor to display accurate colours. Many of the top end monitors are self-calibrating, but for the mid to low end monitors you will need to use a colour calibrator (colorimeter) and suitable software. If you plan on printing your photos yourself you will also need to calibrate your printer. These also range in price and quality.

Colour accuracy is measured in delta-E; the lower the delta-E, the more accurate the colour representation. A delta-E of below 1 is imperceptible to the human eye. Delta-E’s of 2 to 4 are considered good and require a sensitive eye to spot the difference. A delta-E of above 5 should be avoided if you are looking for a monitor for photography.

Contrast Ratio

Contrast ratios are the measurement of the brightest white vs the deepest black a monitor is able to display. High contrast ratios are desirable in monitors for photography because the help to ensure that bright colours look brighter and dark colours look deeper.

There are two common types of contrast ratio; static and dynamic. Static contrast ratios are measured with a consistent backlight level whereas dynamic contrast ratios are measured with a variable black light level. In dynamic contrast ratios the white has been measured with the backlight at full and the black with the backlight virtually off. This is why dynamic contrast ratios are much higher than static contrast ratios.

Response Times

Response times of monitors are generally how long it takes for one pixel to change from one shade of grey to another and is measure in milliseconds (ms). IPS sacrifice response rate for a greater range, depth and accuracy of colour. TN monitors, on the other hand, have poor colour reproduction but fast response times.

Response times are more important for gaming and entertainment than for work with colour but you may be looking for an all-round monitor capable of both accurate colour work and playing games and watching movies. Some modern IPS and PVA monitors have reduced their response times to 6ms, which is still quite a way off the super quick speeds of TN monitors (2ms), but is good enough to handle all but the most intense gaming.