With High Dynamic Range (HDR) now standard on most new TVs, you may have heard of the term “peak brightness” used to describe display performance or picture quality. So what is peak brightness, how is it measured and what does it tell you?
Measuring the peak brightness of a display
Peak brightness refers to the maximum rated brightness of a display. Because of the way some displays limit the brightness of the full field, there are a few ways to interpret this value. Because it is a measurement of luminance ̵
Peak brightness can be measured in “real scene” and “window” values. The actual scene value is the maximum brightness that can be achieved by a screen while watching video content. Reviewers typically use the same reference images to compare one screen to another, providing a realistic comparison of overall screen brightness.
Then there’s the maximum brightness on a window, which only covers a percentage of the screen. For example, a 2% peak brightness window measures the maximum possible brightness in a short time over 2% of the total area of a screen. This is usually measured by displaying a white box on the screen.
Window tests are especially useful for examining how well a screen handles bright HDR highlights, such as a flashlight on the screen. You may also see “sustained window” tests, which test for a longer (sustained) duration. This is useful because many displays dim the longer a bright marker is held on the screen.
Peak brightness applies to both HDR and SDR content, but is especially useful when comparing the much brighter highlights commonly seen in HDR content. The TV review website RTINGS is an excellent source of screen information, with a comprehensive list of peak brightness values for all screens tested.
Display technology makes a big difference
Some displays may become much brighter than others due to the underlying technology, but this does not necessarily result in a higher quality image. For example, LED-lit LCDs get a lot brighter than their OLED counterparts. This makes them particularly suitable for brightly lit environments such as sunny living rooms.
Due to the organic nature of OLED displays, manufacturers use an aggressive Automatic Backlight Limiter (ABL) to prevent damage to the display from heat build-up. This is most noticeable in full-field, bright scenes such as a solid white background. On an OLED, smaller areas of bright highlights can still reach the levels needed for an impressive HDR presentation.
While your viewing environment should play a role in your TV purchase decision, try not to put too much emphasis on peak brightness alone. Many bright LCD models suffer from poor contrast ratio, disappointing black levels and ghosting from dimming algorithms.
OLED models can’t come close to being as bright, making them unsuitable for brightly lit environments, but they have much better black levels and an “infinite” contrast ratio because pixels can be turned off completely.
Make sure you’ve done your research before buying a brand new TV.
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Directors control how bright their movies get
Finally, don’t forget the director’s intention. Many directors are resistant to the idea of overusing HDR and often release their films with relatively few standout highlights.
To put it another way, a movie rated to only hit 300 nits won’t exceed that rating, even when viewed on a production-grade reference monitor capable of over 1,000 nits.
Although HDR has been embraced by many studios, so-called “fake HDR” releases exist.
RELATED: What is ‘fake HDR’ and should you buy HDR Blu-rays?