Displays
Color gamut is the measure of the amount of colors a display can show. Of all the colors the human eye can perceive, only a small amount can be reproduced by displays. The more colors the display can reproduce the “wider” or “larger” the gamut. Displays with smaller gamuts will compress color information into a smaller range - for example, instead of being able to show the sky transitioning from deep space blue to nearly-white sky blue, the display will show a few blues and skip the ones it can’t display. The result will be a sky that looks too blocky, and perhaps will print with more subtlety. There are standardized measures that displays try to achieve that are useful for certain workflows, like movie projection or print. For our purposes, we care about photography and print, which leads us to care about the Adobe RGB color space. Since inks in printers generally produce more colors than electronic displays are able to, it takes a refined piece of electronics to more closely show what a printed page will look like. Finding a display that can display Adobe RGB is nice to have, unless you are primarily focused around a photography and printing press delivery method.
Other color spaces are the sRGB and DCI-P3. SRGB is the target of most consumer electronic displays and is both ubiquitous and useful if you are mostly projecting content or delivering it via the web. It’s rare today to see a display that cannot produce at least 80% of the sRGB color space, although there are some that only manage around 50%. DCI-P3 is a large gamut, like Adobe RGB, but includes fewer blues and cyans. It is the standard that movie projection and production generally aims to use. If you find a display with P3, you will still see more colors than a typical display.
Color accuracy is the measure of how accurately the display reproduces a given color. It is unrelated to gamut, although displays that have wide gamuts typically also have good accuracy. This test sends a color to the display and then measures the color that the display actually produces. For instance, if you ask for “sky blue”, does it miss by adding too much green, or perhaps it’s too light or dark. The unit of measure for this is Delta-E, and each color can be differently accurate. A Delta-E or ∆E of less than 2 is generally considered to be imperceptible, and therefore perfect.
Uniformity is another measure of display accuracy. This one can crop up in both working and presentation. Uniformity is a measure of how even the light of the display is. It is not so difficult to find a modern display that has bright white fringes along at least one edge of the display (“light bleed”). This is very distracting, especially on a black background.
Contrast is the measure of the difference between the darkest black the display can produce and the whitest white. This is different from gamut because it measures just the brightest and dimmest potential of the display, not the colors in between. An old black and white display, which didn’t even display gray, can have a large contrast and essentially no color gamut. This measure is complicated by the possibility of measure both “static” and “dynamic” contrast ratios. The static ratio is the more important, and more difficult, ratio for image quality. This measures the dynamic range of an image as it sits on the screen. A large contrast ratio makes a line easier to see, so it makes drawing, especially for long periods of time, more ergonomic. A “dynamic” contrast ratio measures how dark and bright the screen can be in motion, and uses many tricks to maximize the value. For instance, a static contrast ratio makes stars appear bright on a black space background. However, a high dynamic contrast ratio can show a bright white screen followed by a shadowy alley scene, and achieve brighter brights and darker darks in each scene. But, when confronted with the star field, it will show a sort of dark gray space and a dimmer stars than a display with a higher “static” contrast ratio.
Local dimming, and Full-Array Local Dimming, are related topics. These technologies physically dim the backlight to further increase the contrast ratio, but they can only dime the backlight in certain areas. Even “full array” has, at most, 1200 “zones” of dimming - fewer stars than an image of the night sky would show. These technologies can nonetheless be very useful for motion graphics and movies. They are not, however, so relevant for line drawings.
Brightness or luminance is the amount of light the display can output at its brightest. This is usually measured in cdm^2 or nits - candelas per square meter. A value of around 350 is the baseline for office work. Some higher end displays can achieve 500 or 600, which is enough to work in shade on a sunny day. There are a few displays that can output 1000, and a handful of displays able to output 1500. These displays are designed specifically for movie production and usually only output that much light when in a specific movie mode. 500 is a luxuriously bright image in today’s market.
HDR is a technology that extends the dynamic range of images in consumer displays. HDR signals use 10 bits of information per pixel to increase the amount of brightness or luminance information available for the display to interpret. In order to display this wider range of luminance, displays need to have darker blacks and brighter whites than has typically been available. As discussed above, while most displays achieve about 350 nits of brightness, HDR displays can achieve up to 1000 nits or even 1400 nits and beyond. There is a set of standards that define the HDR capabilities of a display. HDR 400 displays can reach 400 nits, HDR 500 for 500 nits, and so on for HDR 600, HDR 1000, and now HDR 1400. In general, only video content is encoded in HDR, so this certification is not useful for architectural work unless you are focused on producing videos in your firm. Displays with HDR certifications can correlate with producing a brighter image, which is especially useful in a brightly lit office, but this is not universally true. Some HDR displays only exhibit these bright images when the display is in a dedicated HDR mode with an HDR signal, so you wouldn’t see benefits running Revit.
Technologies
All available screens are flat screens. Most use a “light emitting diode” (LED) backlight, often in an array behind the LCD (liquid crystal display) layer. The LCD layer is a translucent sheet of transistors that respond to voltage by dimming. This layer is attached to a filter that allows red, green, or blue light to emit from the backlight through to the user. A set of red, green, and blue transistors, also known as a sub pixel in this context, combine together to make a single pixel. This technology is the dominant form of display technology on the market.
There are few types of transistor layer that behave differently. The three main technologies are IPS, VA, and TN. The details of each technology are less important than their resultant behaviors. IPS (in-plane-switching) produces the best color gamut and color accuracy.
An alternative flat display technology is called organic light emitting diode, or OLED. OLED sub pixels are emissive, meaning that they both produce light and change the amount of red, green, or blue being projected to the user. This allows the displays to be thinner. Because they are organic, the displays are subject to a phenomenon called “burn-in”, where some pixels stop responding to changes in voltage to produce different amounts of light and color. This results in a “stuck image”. This is especially noticeable on computers where the Windows taskbar might be permanently visible on the display, even when viewing photos full screen. The technology has gotten better, but expect an OLED screen to have a lifespan. At monitor sizes and resolutions, they are currently only available to consumers on laptops, although some professional color monitors for movies use the technology. They are available in television sizes of 40” and larger, typically seen at 55” and 65”, from a few manufacturers.