LCD or OLED – Computer displays explained

Displays on Projekt Neptun devices come in many shapes and sizes and they carry all sorts of abbreviations like IPS, WQHD, or sRGB. These abbreviations and the technological details connected to them can tell you a lot about a display’s suitability to a specific workload. With the looming Neptun Wave in mind, it’s the perfect time to explain the key concepts behind the terms used in the Projekt Neptun catalogue of 2017.

Display technology – TN, IPS, and OLED

All displays on current Neptun devices feature either a TFT LCD, or an OLED. TFT LCD stands for thin-film-transistor liquid-crystal display. In general terms, TFT LCDs use a white backlight, an array of liquid crystals that can block or pass through light, and color filters to create an image. Each pixel, which is the smallest individually addressable unit on the display, is usually made up of three liquid crystal elements or subpixels with a red, green, or blue color filter respectively. A single pixel can show different colors by adjusting the brightness of its subpixels. To show black, for example, all light from the backlight is blocked. To show yellow, the red and green subpixels let all light through while the blue subpixel blocks it all. For white, all subpixels are on full intensity. Hence, every pixel can theoretically display all colors, including black and white, and all the pixels of a display together can combine to show any image. Naturally, this process isn’t perfect and there are different approaches to manufacturing TFT LCDs. The Neptun devices that feature an TFT LCDs either use TN or IPS technology.

TN or twisted nematic is the most widely used display technology in laptops. TN panels are fast and cheap. Fast in terms of displays means that individual pixels can switch quickly between different colors or between black and white, which is advantageous for applications like gaming and VR. However, TN displays often suffer from poor viewing angles. This means that when they are viewed at an angle, the colors of the image on the screen shift or even invert. Additionally, TN displays generally show less accurate or vivid colors than other display technologies.

IPS or in-plane switching technology is widely used in cellphones, TVs, and in higher-end computer displays. IPS displays feature better color reproduction and much better viewing angles than TN displays. They are generally slower at switching pixels than their TN counterparts. However, this is only important for the aforementioned use-cases. For anything from office work to watching movies, IPS displays are fast enough. Unsurprisingly, the higher performance of IPS displays also comes with a higher price tag.

OLED or organic light-emitting diode displays are the latest and most expensive display technology on Neptun devices. OLED displays forego the backlight and filters used in LCD technology and instead use subpixels that can light up by themselves, either in red, green, or blue color. Like in LCDs, the subpixels are combined into pixels that can show any color. The big difference is that the intensity of the colors on the display corresponds with the brightness of the individual pixels. Therefore, to show a black pixel on an OLED display, the pixel is simply turned off while in an LCD the pixel tries to block the light from the backlight. This results in much deeper blacks and far higher contrast than in LCDs. Additionally, OLED displays feature great color reproduction, very fast response times, and excellent viewing angles. Their energy consumption on the other hand depends very much on the image shown. With dark images they use quite a bit less energy than LCDs, yet in mostly white images, like in office applications, they may have more of an impact on battery life than previous technologies.

Size, aspect ratio, resolution, and pixel density

Display size is measured in inches going diagonally from one corner to another. The actual real estate on the screen depends not only on the size, but also on the aspect ratio of the display which is given as a fraction of width by height. Most Neptun devices feature an aspect ratio of 16:9 or 16:10 (Apple devices), which corresponds roughly to the ratio movies are shot in and therefore favors media consumption. Some devices like the Microsoft Surface Pro 4 feature a screen with a 3:2 ratio. The larger vertical space of this ratio allows for better use of the screen when writing text or code. It’s common for manufacturers to use marketing terms like “widescreen” to describe the aspect ratio of their product.

The resolution of a display isn’t tied to its size but to its aspect ratio and has to be a multiple of the corresponding fraction. 16:9 displays for instance often feature a resolution of 1920x1080 pixels, also called FullHD. More high-end laptops or recent TVs often show a resolution of 4k/UHD or 3820x2160 which shows exactly four times as many pixels as FullHD. There is a wide variety of different resolutions which are often abbreviated in a complicated manner like UWQHD+ (3840x1600) but the raw numbers are always self-explanatory.

Lastly, the pixel density of a display is a result of its resolution and its size. This means that an 11” display with a resolution of 1920x1080 has a higher pixel density than a 15” display at the same resolution. Pixel density is given in DPI (dots per inch) or in PPI (pixels per inch). The higher the DPI value, the more pixels are available in a given space on the screen to draw the image. A high DPI value results in an overall sharper image which is especially noticeable with text. A high-resolution display with a high pixel density reduces eye strain and allows you to work on your computer for longer periods of time. Values above 200 DPI can be considered to be high, giving a very sharp image. Apple uses the marketing term “retina display” for their high-resolution display. The retina MacBooks feature DPI values of around 220.

Brightness and color reproduction

The value of brightness of a display is important for those who want to use their device outside or for those who require high contrast (difference between darkest and brightest pixel). LCDs often fare better in absolute brightness than OLED displays. However, the latter technology is catching up quickly. High brightness values, like the 500 cd/m2 in Apple’s new MacBook Pros, are indeed always welcome, as a bright display can easily be dimmed, but a dim display can’t be made brighter. Naturally, as displays are one of the components with the highest impact on battery life, a display set to high brightness can also have you looking for an outlet much faster.

Good color reproduction means that a display is firstly capable of showing many different shades of colors and secondly that an individual color looks as it is expected. Many displays are only capable of or calibrated towards the first requirement. This can be seen in electronics stores where TVs are set up in a showroom mode where all colors are displayed extremely vividly. Thus, a man might have a red face instead of a more natural skin tone, but at least the color really pops. For media creation, however, it is usually very important that the colors are accurate. General measures of color reproduction are given by a display’s cover of a gamut or color spectrum like sRGB, Adobe RGB, or DCI-P3. Device manufacturers like to give values like “covers 98% of sRGB” which means that a display is able to show almost all colors defined in this color spectrum. However, a display also needs to be calibrated to accurately show these colors. HP, with their line of Dreamcolor displays, and Microsoft, with the Surface Pro 4, calibrate their displays to sRGB during production, so they’re accurate out of the box. Lenovo even includes a built-in calibrator in its P50 that allows you to calibrate the display yourself to any color spectrum you require. In general, if a device has an accurate display and covers certain color spectrum, the device manufacturer will advertise it.

Conclusion

Good, high-resolution displays aren’t just important for media creators, but also for people who read a lot on their devices. A high pixel density reduces eye strain and a bright display allows you to work outside. For most people, it is enough to look at the raw numbers of size, resolution, and brightness, and, if possible, to check out a display in the wild to find out if it fits your needs. Additionally, IPS and OLED displays are almost always better than TN displays. For media creators on the other hand, it’s also important to take a look at the color spectrum a display covers and to read independent reviews of a particular device to see if it checks all required boxes. General information about all displays can be found in the Projekt Neptun catalogue, while more in-depth specifications may be available on the websites of device manufacturers or in independent reviews.

As always, you can see and compare all our devices at the Demo Days during our next Neptun wave where our helpful staff will try to answer all your questions. If you can’t make it to the Demo Days, feel free to visit us at our Help Points in Zurich, Basel, and Lucerne or to write us at kontakt@projektneptun.ch.