HDR screens are screens that display color-accurate images with excellent exposures and contrasts. In order for a display to be HDR, it must meet the main specifications set out by certification bodies such as VESA. After a product passes certification, it can be advertised as an HDR display.
While HDR logos and markers are useful for quickly identifying an HDR display, relying solely on these logos can be confusing and often not enough to determine whether a display can truly provide great visuals. Here are five HDR specs you’ll want to check out to make sure you’re getting a truly HDR-compatible display.
1. Color gamut
A color gamut represents all the colors a screen can display. Suitable HDR displays use a color space known as Rec.2020. This color space covers 75.8% of the CIE 1931 color space (theoretical colors visible to the human eye), a major upgrade from sRGB and Rec.709 used in SDR displays. Here is an illustration comparing the difference between Rec.2020 and Rec.709:
As you can see in the image above, Rec 2020 can display more colors than Rec. 709. Although it is often thought that HDR displays Rec. 2020 there are HDR certified screens that can only display the sRGB color gamut.
To make sure your screen is actually HDR compliant, scan through the screen specs and look for “Rec. 2020” or “BT. 2020”. If the specs don’t mention the color gamut, it’s best to buy your HDR display from a reputable brand and avoid cheap displays from companies you’ve never heard of.
2. Color depth
Unlike the human eye, which perceives frequencies of light (colors) in an analogous way, digital displays with numbers need to be told which shade of a color to display. Color depth or bit depth speaks about the gradient of a specific color. The higher the bit depth, the more gradients or shades of a color a screen can display. Low color depth leads to color transitions, causing streaks.
HDR displays have a color depth of 8 to 12. An 8-bit color depth can display 16 million colors, which isn’t much of an upgrade from a regular SDR display. A 10-bit display can display up to 1.07 billion colors and a 12-bit display can display over 68 billion colors!
Because the human eye can only see so many colors, the visual improvements you get from a 12-bit display as opposed to a 10-bit display are minimal, if not noticeable. So unless you’re editing 12-bit videos or want to future-proof your screen, a 10-bit screen is all you need to watch HDR movies on the best streaming platforms.
3. Peak Brightness
Color spaces are often represented as 2D artwork with all the hues (unchanged primary and secondary colors) a screen can display. The truth is that color spaces are actually three-dimensional. The third dimension represents the brightness of a color.
The brighter your screen can get, the brighter colors your screen could display and the better the images will be visible in a bright environment. Having a higher peak brightness also adds a bit to a screen’s dynamic range and contrast.
In digital displays, luminance or brightness is measured in nits or candela per square meter (cd/m2). For HDR displays, the minimum brightness is 400 nits (400 cd/m2) and the maximum is 4,000 nits (4,000 cd/m2). In general, the higher the brightness of a screen, the better.
To make sure you get an HDR display capable of great contrast and dynamic range, in addition to maximum brightness, you need to consider the contrast ratio and the type of dimming or backlighting technology the display uses.
4. Contrast Ratio:
While peak brightness is all about how bright a screen can get, the contrast ratio is the difference between the brightest white and darkest black on the screen. A display with a good contrast ratio can more realistically display high-contrast scenes that require high dynamic range: people behind a sunset, city lights at night, and explosions in a dark environment.
A display with a poor contrast ratio can result in faded colors and reduced details in very bright and dark scenes.
For displays with TN, VA or IPS panels, a contrast ratio of 3,000:1 would be a good start.
According to RTINGS, a good contrast ratio would start at 3,000:1 for displays with TN, VA, and IPS panels. A higher contrast ratio generally means a higher dynamic range.
Also keep in mind that there is a bell curve or decreasing efficiency as the contrast ratios get higher. So you would at least want a 3,000:1 contrast ratio, but it would be better to find one with a higher contrast ratio, like 20000:1, or even those with infinite ratios.
5. Local dimming
The contrast ratio determines how bright and dark a screen can become. The problem is, it doesn’t say much about how a screen is lit.
Local dimming is one of the most important aspects of HDR. Local dimming is the ability of a display to dim the brightness of a specific area or zone on the screen. A display with local dimming can dim hundreds of zones in a screen, which greatly improves the contrast. Without local dimming, edge-lit displays on a typical TV or monitor would only have about 1-16 dimming zones.
While local dimming is required for most HDR displays, there are HDR certifications that don’t require local dimming, such as VESA’s DisplayHDR 400. So to make sure you get a good quality HDR display, buy a spec display stating “Local Dimming” or “Full Array Backlight” – or just take an OLED screen.
Unlike your typical LED panels like TN, VA, and IPS, OLED panels don’t use a backlight to illuminate their pixels. Instead, OLED uses thin carbon-based semiconductor plates to provide light. This allows OLED screens to have a contrast ratio of infinity to one and local dimming zones to have as much as the number of pixels of the screen.
An OLED HDR screen provides the ultimate contrast ratio. However, there are two reasons why you could opt for a full array display instead. The first reason is that OLEDs are expensive. The second reason is that the brightest OLED displays only have about 700 nits of peak brightness. So if you plan to use your screen in a brightly lit room, an OLED screen may not be bright enough to reduce glare.
Alternatively, you can choose a QD-OLED TV that gives you the best of both worlds: rich, deep blacks and bright, crisp whites.
Things to Remember Before Buying an HDR Display
Here are the top five specs to look for when buying a new HDR display. Remember: check the display’s color gamut (BT2020/Rec.2020), color depth (10-bit or 12-bit), peak brightness (400-4000 nits for full-array displays), contrast ratio (3,000:1 or higher), and whether it has local dimming capabilities.
Also remember that a screen should have good levels of peak brightness, contrast ratio and local dimming as these go hand in hand to provide high dynamic range in a screen.
Finally, keep in mind that DisplayHDR XXX is different from HDR XXX when looking for HDR related logos and trademarks. For example, DisplayHDR 600 is a much better certification as it tests a screen’s color gamut, bit depth, and peak brightness. In contrast, HDR 600 only shows that the display can handle a peak brightness of 600 nits.