With so many terms and phrases floating around, it can be an exercise in patience to nail down what exactly any given display brings to the table. A display could be HD, UHD, HR, 4K, or 8K, but without any context, these classifications are not all that telling. If the only thing you know about a display is its resolution, you do not actually know all that much. It can be difficult to keep track of all the terminology used in and around the large-format digital display industry, but to help you arrive at a more fluent understanding of digital display tech, we would like to explain some of the context that’s found behind the various terms and phrases you’ll encounter. To do so, let’s start small.
The smallest addressable building block of a digital display is the pixel, and it is through the counting of these pixels that the resolutions of displays are discussed and compared. The resolution of any given display describes the numbers of pixels it employs in its dimensions, and refers only to those numbers; it has no qualitative bearing on the clarity or sharpness of a display. It is only a quantitative measurement. In order to understand the relationship between the resolution of a display and its actual sharpness, you must also know the display’s pixel pitch. The pixel pitch of a display is the distance between the centers of two adjacent pixels, and the smaller the pixel pitch, the finer the picture appears. Smaller pixel pitches imply a tighter image sharpness, but that does not always mean a smaller pixel pitch is better; pixel pitch must be considered within the context of the display’s usage. If your audience sees your display from a viewing distance of a few hundred feet, a pixel pitch in the low single-digit millimeters is entirely unnecessary. In general, the closer your audience will be to the display, the smaller your pixel pitch should be. Therefore, figure out the viewing distance of your audience first, and then arrive at a pixel pitch that makes sense. Once you’ve done that, the resolution of your display is simply a function of how physically large it is.
HD, HR, 4K, & 8K
The most commonly used phrase regarding the resolution of digital displays of any format is of course “high-definition.” For a display to qualify as HD, it typically must meet a few separate thresholds. Chiefly, it must incorporate a 16:9 aspect ratio, and exhibit a 1920×1080 pixel resolution. Because of these requirements, whether or not a display qualifies as high-definition is not only a function of its pixel count, but also of its shape. For that reason, asking whether a display is high-definition is not always a helpful question. A display can present an incredibly sharp picture and still not count as high-definition, which is why the phrase “high-resolution” is often more useful. Though sometimes used interchangeably with high-definition to describe the clarity of a given display, high-resolution technically has a different meaning. A more subjective term not measured by any hard metrics, high resolution simply describes any display that is especially sharp.
In recent years, you have probably heard the phrase “4K resolution,” tossed around with growing frequency. 4K resolution, also called Ultra HD, or UHD, is used to describe displays that have a total resolution of 3840 pixels by 2160 pixels. Just below 4,000 pixels in its width (hence “4K”), this resolution quadruples the pixel count of standard HD while maintaining the 16:9 aspect ratio. Using this same logic, you can come to the conclusion that 8K resolutions are those with sixteen times the pixel count of standard HD. These resolutions are rare, and are almost exclusively found in the cinema space on extremely large displays viewed from quite close distances.
Displays with 4K resolutions do not have sharper picture quality simply because they have more pixels than standard HD displays. They have sharper picture quality because they have more pixels than standard HD displays within the same physical area. This is why it is so important to understand pixel pitch. A 4K display will always contain four times as many pixels as a traditional HD display, so if they share the same physical dimensions, the 4k will thus will need to employ a pixel-pitch that is half as large. Conversely, a 4K display with the same pixel pitch as a standard HD display must be twice as wide and twice as tall in order to fit all its extra pixels.
Manufacturers might advertise resolutions of their displays in an attempt to wow prospective customers, but as you hopefully now can see, the resolution of a display is not the only detail that matters with regard to digital display picture quality. Resolution is important, certainly, but without the other details of the display, all it tells you is the number of pixels. To really get a feel for the quality of the display picture, you need to know more. For a deeper dive into how resolution, viewing distance, and pixel pitch work together, download our white paper, Pixel Pitch: What is it? Why Does It Matter?