Reference

Glossary of display terms

The vocabulary of specification sheets, defined briefly and without jargon. Each entry points to the chapter of the handbook that treats it in depth.

Adaptive-Sync: The VESA standard for variable refresh rate over DisplayPort. FreeSync and G-Sync Compatible are built on it. See refresh rate.
Arcminute: One sixtieth of a degree. An eye with 20/20 vision separates two details one arcminute apart, which sets the threshold of 60 pixels per degree. See pixel density.
Aspect ratio: The ratio of the width of the image to its height: 16:9 for standard monitors, 21:9 for ultrawide, 32:9 for super ultrawide, 16:10 for some office screens.
Backlight: The light source behind an LCD panel. It shines permanently; the liquid crystals in front of it block more or less of its light.
Banding: Visible steps in a gradient that should be smooth, caused by too few levels per colour. A 10-bit signal reduces it. See colour.
Bit depth: The number of bits used for each primary colour: 8 bits give 256 levels and 16.7 million colours, 10 bits give 1024 levels and 1.07 billion colours.
Blooming: A halo around a bright object on a dark background, on screens with local dimming, because the lit zone is larger than the object.
Burn-in: A permanent ghost image left on an OLED panel by an element displayed in the same place for thousands of hours. See panel types.
Colour space: A standard set of colours defined by three primaries and a white point: sRGB, DCI-P3, Adobe RGB, Rec. 2020. An image is encoded for one colour space.
Contrast ratio: The brightness of white divided by that of black on the same screen. About 1000:1 for IPS, 3000:1 to 5000:1 for VA, unlimited for OLED.
Curvature (R): The radius, in millimetres, of the circle a curved screen follows. 1800R is a gentle curve, 1000R a tight one.
DCI-P3: A colour space from digital cinema, about a quarter larger than sRGB, used for HDR video and by recent phones under the name Display P3.
Delta E (ΔE): The measured difference between the colour requested and the colour displayed. Under 1 it is imperceptible, under 2 it is very good.
DisplayHDR: The VESA certification for HDR monitors. The number is the peak brightness in nits: 400, 600, 1000, 1400; “True Black” levels apply to OLED.
DisplayPort: The video link of computers. Version 1.4 carries 25.9 Gbit/s of image data, version 2.1 up to 77.4 Gbit/s. See connections.
DisplayPort Alt Mode: The mode in which a USB-C port carries a DisplayPort signal on its high-speed wires. It is what makes a USB-C port a video output.
DSC: Display Stream Compression: a visually lossless compression of the video signal, by a factor of up to three, used for high resolutions at high refresh rates.
Flicker-free: Said of a monitor whose backlight is dimmed by lowering the current, not by switching it on and off. See eye comfort.
FRC: Frame rate control: rapid alternation between two neighbouring levels to simulate an intermediate one. “8 bit + FRC” approximates a 10-bit panel.
Frame time: The duration each image stays on screen: 1000 divided by the refresh rate. 16.7 ms at 60 Hz, 6.9 ms at 144 Hz.
FreeSync: AMD’s name for variable refresh rate. Its levels (FreeSync, Premium, Premium Pro) add requirements on the range and on HDR.
Gamut: The range of colours a screen can display, the triangle formed by its three primaries. Expressed as coverage of a colour space, for example 95% DCI-P3.
G-Sync: Nvidia’s name for variable refresh rate. “G-Sync Compatible” monitors use the Adaptive-Sync standard and are validated by Nvidia.
GtG: Grey to grey: the usual measure of response time, the duration a pixel takes to pass from one shade of grey to another.
HDMI: The video link of televisions and consoles, also present on monitors. Version 2.0 carries 4K at 60 Hz; version 2.1, up to 4K at 144 Hz and beyond.
HDR: High dynamic range: images encoding highlights far brighter than ordinary white and details in deep shadows. Requires a very bright screen with local dimming, or OLED.
Input lag: The delay between the arrival of a signal at the monitor and the display of the image. Under 5 ms on good monitors; far more on televisions outside game mode.
IPS: In-plane switching: the LCD technology with the most stable colours and the widest viewing angles. Contrast about 1000:1, twice that for IPS Black.
KVM: A switch built into some monitors that moves keyboard, mouse and other USB peripherals from one computer to another along with the video input.
Local dimming: Division of an LCD backlight into zones that are dimmed independently behind dark areas of the image, to deepen blacks.
Mini-LED: A backlight made of thousands of small diodes in hundreds or thousands of zones. It gives an LCD high brightness and effective local dimming.
MST: Multi-Stream Transport: DisplayPort’s ability to feed several monitors from one output, by chaining them or through a hub. Not supported by macOS for extending the desktop.
Nit: The unit of screen brightness, equal to one candela per square metre (cd/m²). An office screen is used at 100 to 150 nits; HDR highlights reach 1000 and more.
OLED: Organic light-emitting diode: each pixel emits its own light and can switch off completely, giving perfect blacks and near-instant response.
Overdrive: Acceleration of pixel transitions by briefly over-driving them. Set too high, it produces bright trails behind moving objects (overshoot).
Pixel pitch: The distance between the centres of two neighbouring pixels, in millimetres: 25.4 divided by the PPI.
Power Delivery: The USB standard by which a monitor charges a laptop through the USB-C video cable. Monitors supply 65 to 140 W.
PPD: Pixels per degree: the number of pixels inside one degree of the field of view at a given distance. The measure of perceived sharpness; 60 PPD matches 20/20 vision. Try the calculator.
PPI: Pixels per inch: the density of a panel, computed from its resolution and diagonal. 109 PPI for a 27-inch 1440p screen, 163 PPI for a 27-inch 4K screen.
PWM: Pulse-width modulation: dimming a light by switching it on and off rapidly. At low frequency it can cause visible flicker and discomfort.
QD-OLED: An OLED panel whose blue light is converted into red and green by quantum dots. Very pure colours; triangular sub-pixel layout.
Refresh rate: The number of images the monitor displays per second, in hertz. 60 Hz is the base, 144 Hz the base for games.
Response time: The duration a pixel takes to change shade. It must stay under the frame time for motion to be clean.
Scaling: The operating-system setting that enlarges the interface on dense screens: 125%, 150%, 200%. It trades workspace for sharpness. See resolution and scaling.
sRGB: The standard colour space of the web, office software and most games. An image without a colour profile is assumed to be sRGB.
Sub-pixel: One of the red, green or blue elements that make up a pixel. Their arrangement (stripe, triangle) affects how text is rendered.
Thunderbolt: A link using the USB-C connector with a guaranteed 40 Gbit/s (80 for Thunderbolt 5), carrying video, data and power on one cable.
TN: Twisted nematic: the oldest LCD technology, fast and cheap, with poor colours and narrow viewing angles.
Uniformity: The consistency of brightness and colour over the surface of the screen. Monitors for image work compensate for it electronically.
VA: Vertical alignment: the LCD technology with the highest native contrast, 3000:1 to 5000:1, and slower dark transitions.
VESA mount: The standard pattern of four threaded holes on the back of a monitor, usually 100 × 100 mm, for arms and wall mounts.
Viewing angle: On this site: the horizontal angle the screen fills in the field of view, from the seat. On specification sheets: the angle from which the image remains acceptable.
VRR: Variable refresh rate: the monitor displays each image when the graphics card delivers it, which removes tearing and stutter.
White point: The colour of white on a screen, given as a colour temperature. The standard is D65, a daylight white of about 6500 K.