How bright is bright? The difficulty of comparing LCD and AMOLED displays
The resolution race continues to drag on in the smartphone ecosystem, but it’s getting harder to impress simply by cramming more pixels into a display. With 2560×1440 fast becoming the de facto standard for flagship screen resolution, we need a new metric to separate the weak from the strong. Display brightness might be it — Samsung made a big deal about brightness with the Galaxy S5 announcement, and low brightness is what kept the LG G3’s display from being truly great.
It’s easy to measure resolution, but brightness is a different story, especially with AMOLEDs. In fact, there’s been some dispute over how to measure AMOLED display brightness and who has the right numbers. For example, Anandtech reported the Nexus 6 display brightness peaked at 258 nits, whereas others have listed 400 nits as the maximum brightness. So who’s right? Technically, everyone might be right — they’re just right in different ways.
AMOLED displays are very simple and consist of just a few layers — which is why they’re usually more flexible than LCD displays, too.
LCD and AMOLED are the two different types of display technology commonly used in smartphones. LCD is an older technology, and these brightness readings aren’t really in doubt. LCDs rely on banks of LEDs to shine light through the liquid crystal array to produce the desired colors. These LEDs have a maximum brightness, and the amount of light that can reach the user is dictated by the size and number of pixels.
Read: Dell unveils 5K desktop monitor with almost 2x the pixels of your puny 4K display
AMOLEDs are newer technology and have started showing up in many of the top smartphones. Measuring the brightness here is less of an exact process because of the way AMOLEDs produce light. Rather than have a separate backlight, the photons are produced directly by each subpixel, which can shine red, blue, or green when voltage is applied. If you want to display black, the AMOLED pixels are simply off. This is probably the most well-known property of AMOLED technology — it uses less power displaying black images.
Where things get tricky measuring AMOLED brightness is with the image used to test it. Unlike LCDs, there is no agreed upon maximum brightness for an AMOLED pixel. There’s a property of AMOLEDs called Average Pixel Level (APL), which is the number of pixels that are lit expressed as a percent. A black screen is 0%, all white is 100%, and a red/green/blue screen would be 33%. When fewer pixels are in use (i.e. low APL), the display can allocate more power to individual pixels, meaning they put out more light in the lit areas. At 30% APL the Nexus 6’s screen can output over 400 nits, but at 100% (all white), it’s about 250 nits.
So, no one is really wrong here, even though they have very different numbers. It’s theoretically possible to produce higher brightness levels with an AMOLED, measure that, and call it the maximum. However, in daily use, most images have fairly high APL. This is especially true in Android 5.0, which has more white UI elements. For instance, Lollipop’s settings screen is about 84% APL.
Anandtech uses 100% APL in its measurements, hence the confusion over “maximum” numbers. In real life, you might see 20% more brightness thatn these reported values, but relying on numbers that were obtained with very low APLs (i.e. 400 nits for the Nexus 6) is simply unrealistic. The truth is somewhere in between.
Now read: OLED finally triumphant: The Galaxy S5 has the best smartphone display on the market
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