Computer Monitors And Display Colours : OSH Answers

The image contrast is given by the ratio between the brightness of the "white" and the brightness of the "black" that the monitor can reproduce. A higher contrast of the display can give the impression of increased brightness and can increase the capacity to notice details.

There are two types of contrast ratios: "static" contrast ratio and "dynamic" contrast ratio.

The "static" contrast ratio is the contrast ratio that can be produced at any moment in time, and is determined by calculating the ratio between the brightness of "white" and the brightness of "black" within a single picture on a display situated in a completely dark room. For example, a static contrast ratio of 1000:1 means that the black images on the screen are 1000 times darker than the white images.

The "dynamic" contrast ratio compares the brightest whites and the darkest blacks from different scenes of moving images on the screen. The display equipped with dynamic contrast ratio (DCR) has the ability to make dark scenes even darker by adjusting the intensity of the backlight. In this way, the ratio between the luminosity of the whitest white among all images and the darkest black from all images increases. As a consequence, the dynamic contrast ratio is always much higher than the static contrast ratio.

The monitors used in offices do not usually have DCR technology, so they are characterized by the "static contrast ratio".

High dynamic range (HDR) allows a wider range of colours and brightness, and greater detail in images. It requires an HDR-compatible display with a recommended brightness of at least 300 nits. Additionally, the content needs to be intended for HDR viewing in order to benefit from its advantages. The benefits of HDR are most pronounced when image quality is important, such as when watching videos or pictures, and less significant for common computer tasks, such as word processing.

Organic light-emitting diode (OLED) monitors work differently from the more common liquid crystal display (LCD) monitors by turning off pixels when they need to display black. That results in a much higher contrast than capable with an LCD monitor. One major disadvantage of OLED monitors is the potential for "burn in" - that is, some static images can stay (or "burn") on the screen permanently when the displayed content does not change for an extended period of time.

Sharp images and adequate contrast ratios are typically required to make a display easier to read.

The human eye can perceive changes in contrast up to about a 1000:1 ratio. Changes are more noticeable when we pass from a 10:1 contrast ratio to a 20:1 contrast ratio. As the contrast ratio increases, the difference is noticed less. For example, the difference in contrast at ratios higher than 500:1 up to 1000:1 will seem minor. The contrast perceived by the viewer will always be less than the given contrast ratio for the monitor. This difference is due to the fact that the monitors are usually in an office setting, where the reflection of the surrounding light will reduce the contrast.

What is acceptable to an individual will also depend on character size, viewing distance and the type of task being done. A properly functioning monitor will typically provide adequate resolution and a static contrast ratio of up to 1000:1.