EMZETT.Screen
In short: The display surface of a device on which graphical content is shown — as a standalone device (monitor) or built in, e.g. on laptops and smartphones.
In more detail: Common technologies are LCD (with backlighting) and OLED (each pixel lights up on its own, giving true black and high contrast). Key specs include resolution, screen diagonal and refresh rate.
In Depth
Key specs: resolution, diagonal, pixel density
The image quality of a screen depends on several, partly independent specs: resolution (e.g. 1920×1080 “Full HD”, 2560×1440 “QHD”, 3840×2160 “4K/UHD”) gives the number of pixels, the screen diagonal (in inches) the physical size — the same resolution looks sharper on a small screen than on a large one, since the pixels are packed more densely (pixel density, measured in PPI, pixels per inch). A 27-inch 4K screen therefore looks considerably sharper than a 65-inch 4K TV, even though both have the same number of pixels.
Refresh rate
The refresh rate (e.g. 60 Hz, 144 Hz, 240 Hz) states how often a new image is built up per second — important for the perceived smoothness of motion, for example in games, fast scrolling or mouse cursor movements. Higher refresh rates also reduce the perceived input delay (latency) between mouse movement and the visible reaction on screen, which matters especially in competitive games. A precondition for this, however, is that both the graphics card and the respective program can actually deliver that many frames per second (FPS) at all — a 240 Hz screen brings no benefit if the graphics card only computes 60 frames per second.
LCD vs. OLED
In panel technology, LCD and OLED stand opposed: LCD panels need a separate backlight that shines through a liquid crystal layer — true black is barely possible with this, since the backlight is never fully turned off (modern “mini-LED” LCDs mitigate this with very many individually dimmable lighting zones, but don’t reach OLED’s perfection). OLED panels, by contrast, consist of self-illuminating pixels that can each be turned off completely, leading to very high contrast and deep black, but with the risk of “burn-in” (permanent discoloration through uneven ageing) with image content that stays static for a long time, such as taskbars or channel logos.
Synchronisation
Technologies like V-Sync/sync ensure that the graphics card’s image output and the screen’s refresh rate run in sync, to avoid image errors like “tearing” — where parts of two different, time-shifted frames become visible in a single displayed image, because the graphics card and screen are working unsynchronised. Modern adaptive methods like AMD FreeSync or Nvidia G-Sync dynamically adjust the screen’s refresh rate to the frame rate actually delivered by the graphics card, instead of rigidly synchronising to a fixed rate.
Colour space and HDR
Besides resolution and refresh rate, the colour space covered (e.g. sRGB, the wider DCI-P3 or Adobe RGB) determines how many different colours a screen can display at all — a screen with limited colour space coverage shows rich colours (e.g. strong red or green) more faded than intended in the original material. HDR (High Dynamic Range) additionally extends the contrast range between the darkest and brightest displayable areas of an image at the same time, which creates a considerably more natural impression than classic SDR (Standard Dynamic Range), especially in scenes with very bright light sources alongside very dark shadows (e.g. sun through clouds). Real HDR requires sufficiently bright backlighting (for LCD) or high peak brightness (for OLED) for this — many cheap “HDR-capable” screens only barely meet the certification criteria and show barely any visible difference from SDR.
Response time and ghosting
Besides refresh rate, response time (usually given in milliseconds, e.g. 1 ms) is a second, often-confused spec: it describes how quickly a single pixel can switch from one colour to the next, not how often a new image is built up per second. If the response time is too slow for the set refresh rate, “ghosting” occurs — a visible trail behind fast-moving objects, because the previous image isn’t fully faded out yet when the next one is already displayed. LCD panels with TN technology traditionally achieve the shortest response times, IPS panels (better colour accuracy and viewing angles) are usually somewhat behind, and OLED panels are practically delay-free thanks to their self-illuminating pixels.
See also: Monitor, V-Sync, FPS, Graphics cards