The display is arguably the most important piece of hardware on any television, computer, tablet, or smartphone. Yet displays are also difficult to explain and understand. They can be measured, but most people are not familiar with what those measurements mean or how they relate to their own viewing experience.
Contrast. Black level. Gamut. Uniformity. These words can seem like arcane scrawl to the initiated, but they’re actually not difficult to grasp. Here’s our guide to the terms you need to understand when considering a notebook display, along with what to look for in each one.
Contrast ratio – Not really 1,000,000,000:1
This phrase is one that you’ve almost certainly heard before. Display manufacturers love to use contrast ratios because of all the impressive zeros they get to slide in. Numbers are easy to understand, and the higher they are, the better their display seems on paper.
Contrast ratio is simply the ratio of luminance between the brightest color (white) and darkest (black) on a display. Higher ratios are considered better because it means images will appear more defined and realistic.
There’s just one small problem. No one uses a standardized test for contrast ratios. There are many ways to fudge the results, which is why there are inexpensive displays that claim insane ratios like 10,000:1.
You should trust contrast ratios as they’re reported in reviews. In-depth analysis using identical testing methods and equipment is the only way to discover a display’s true contrast.
Brightness is important for mobile devices like laptops, smartphones and tablets. Most devices have a glossy display to enhance contrast, but the gloss makes reflections an issue in bright rooms or outdoors. These reflections can only be defeated by a bright display.
The Nit is the standard unit of luminance used to describe various sources of light. A higher rating means a brighter display. Displays for laptops and mobile devices are usually between 200 and 300 nits on average. A rating over 300 nits is solid and a rating above 500 nits is extremely good. Only a few devices can put out that much light. Televisions are a different story, and the brightest go north of 1,000 nits.
Seeing in black and white
Reviews of displays, including ours, will often make reference to black levels. You might be able to infer that this has something to do with how the display renders black, but it doesn’t explain much else.
Black level itself is expressed in a number, with lower being better. A black level of 0 represents a dark, pure black. The number is relevant because it has influence on how a display handles dark images. If you ever watch a movie on a bad display you will notice that details are missing from dark scenes. That’s because the display isn’t capable of reproducing the darkest portions of the image.
White levels are the opposite. The higher the value, the better. A white level of 255 is the maximum on the RGB scale, so an ideal display will come close to that figure and display a bright, unblemished white. Modern displays have a better handle on white levels than they do black levels, so it usually is not a defining quality. But an exceptionally good or bad result can make a difference.
A journey through space
Microsoft and HP collaborated in 1996 to create a standard color space known as sRGB. As you might imagine, it’s most relevant to computers. A color space is a standard gamut of colors that displays should be capable of reproducing.
What you might not know is that many monitors can’t handle even three-quarters of sRGB. An average laptop display, mobile device, or entry-level monitor can usually display only 65 to 75 percent. A mid-range IPS display can usually handle 90 percent or better. Only a top-tier IPS display can handle it all.
There are many others standards and some have a wider color space than others. It’s always better for a display to reproduce a higher percentage of a color space, but results can only be compared between products if they were tested using the same standard.
Respect the uniform
Almost all displays on the market today use LCD technology. This technology has been refined so that it’s inexpensive and of high quality, but does have a few drawbacks. Among these is the fact the panel itself emits no light.
For a picture to be visible a light must be shown through the LCD. In an ideal world the light behind the LCD would be equally bright in all areas, but that’s easier said than done. Most displays are at least a bit brighter in some areas than in others. This is a uniformity issue.
We have tested displays with uniformity issues that were severe enough to be immediately noticeable by an untrained eye. The problem is most obvious during dark scenes and is most prevalent in mobile devices. Plasma and OLED don’t have this problem because they create their own luminance.
Getting the band together
We commonly use a banding test image when looking at a display. This image displays a gradient of shades between absolute black and absolute white. A perfect product will display the image as butter smooth, but most don’t. Bands often appear in the image and are most common in its darkest quarter.
Banding is a noticeable problem. It’s common in any content that depicts a grade of color that gradually shifts. A photograph of a sunset is a great example. Banding will cause the photograph to have unnatural layers of color that shift abruptly.
Don’t dither about
A similar issue is dithering. This technique carefully arranges the colors a display is capable of producing to replicate a color it can’t product. For example, let’s say a display for some reason could not produce purple hues. It could instead try to replicate the color with alternating red and blue pixels.
Dithering is used to combat banding, but we’ve noticed cases where dithering just doesn’t seem to work properly. It can cause strange results such as expanses of flat, shimmering blacks in our gradient banding image. That’s the sort of problem that could become a serious issue during real-world use.
The screen door effect
“Screen door effect” is a phrase used to describe a monitor that has a visible gap between individual pixels. The technical term for this phenomenon is “dot pitch,” which describes the size of individual pixels and the distance between them. A low dot pitch means gaps should not be easily visible, while a high dot pitch means the opposite.
The impact of dot pitch is relative to the device. The gap between pixels becomes easier to notice as the distance between the display and its user decreases. That is why dot pitch is most often a problem on a mobile device. Monitors and HDTVs usually don’t struggle with this problem because the user is much further away.
Hopefully this explanation has helped you understand how displays are measured. We do not refer to these terms in every review because we want to make our reviews as approachable as possible, but sometimes it’s impossible to avoid the technical talk. Now you will know what we’re on about.