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Brightness, Black Level, Contrast Ratio, And Gamma
Brightness
Brightness (also referred to as white level) measurements are taken by recording the luminance output of each device displaying a full white pattern, with the device’s brightness slider set to minimum and maximum values.
The Meizu MX3 achieves the lowest minimum brightness level, while Oppo's N1 brackets the group on the high end at 17.5 nits. Fortunately, all of these devices get dim enough that they won’t sear your retinas when you use them in the dark.
The backlight in the iPhone 5s outshines all others. With a much smaller screen to illuminate, Apple can spare some extra juice for its pixels without taking a huge hit out of battery life. That's a luxury the larger screens can’t afford.
Oppo’s N1 also gets very bright at over 400 nits, coming in just behind the iPhone 5s. Oppo overshadows its remaining competition, although all of the devices (except the rather dim AMOLED display in the Note 3) get acceptably bright.
In order to make device comparison possible, the rest of our display measurements, along with our battery testing, are performed with the screen set to a standardized white level of 200 nits.
Black Level
Our black level measurement is the luminance output of a full black pattern after the luminance output of full white has been standardized to 200 nits. AMOLED displays will always measure a black level of zero, since their pixels simply turn off to render black.
The Note 3's Super AMOLED screen wins this test by default by producing a true black. The N1 also performs well, placing ahead of the iPhone 5s. The impressive black level recorded while running ColorOS (half the value achieved when running CyanogenMod) suggests that Oppo provides some screen optimizations for its in-house OS.
Contrast Ratio
Contrast ratio is the difference between a full white pattern and a full black pattern. Due to their zero reading on black level tests, AMOLED displays are said to have an infinite contrast ratio.
The N1 shows the best contrast ratio of the group, if we ignore the Note 3’s infinite result. The N1/ColorOS combination, with its low black level, achieves an astounding ratio of 1706. Even without the tweaks in ColorOS, the N1 still manages a better contrast ratio than the iPhone 5s. The screens in the Mi3, MX3, and Nexus 5 all have ratios below 700, negatively impacting their display quality compared to the chart's top end.
Gamma
Gamma compensates for the linear brightness levels displayed by a screen, versus the nonlinear way our eyes perceive light. A gamma curve of 2.2 is what we want to see, as a screen with a gamma less than 2.2 appears brighter and with less shadow detail, while a gamma larger than 2.2 displays heavy shadows with fewer highlights.
The factory-calibrated screen in the iPhone 5s gets closest to the optimal gamma value. The Note 3 and N1 with ColorOS also come close, while the Nexus 5 is the furthest from ideal.
Color Temperature
Color temperature is a measurement in Kelvin, which is used to describe how “warm” or “cool” a given display is. Ideally, as long as you're not viewing your device in direct sunlight, this should be in the 6500 range. Higher color temperatures result in a cool, bluish hue, while lower temperatures deliver a warm or reddish tone.
All of the tested devices have a color temperature above 6500, but the higher temperatures displayed by the MX3 and Note 3 give their screens a noticeable blue tint. The Mi3 comes closest to the ideal value, while the N1 is only about ten percent over, regardless of operating system.
Color Gamut
Our volume measurements are compared against both the sRGB and AdobeRGB color gamuts. A reading of 100 percent on sRGB and 72 percent on AdobeRGB is optimal for viewing the vast majority of digital consumer content. A lower reading is typically accompanied by an overly red or yellow image. Meanwhile, a higher reading is usually too blue/green.
The Note 3 manages to appear as a wide-gamut display in the sRGB color space, easily surpassing the 100 percent mark, which tends to produce overly vibrant, or “neon,” colors when viewing standard sRGB content. Curiously, it only covers 59 percent of the AdobeRGB color space, the second-lowest overall.
When running CyanogenMod, the N1 displays a respectable 91 percent of sRGB and 63 percent of AdobeRGB. However, with the screen controlled by ColorOS, coverage drops to only 77 percent of sRGB and 53 percent of AdobeRGB. This is disappointing, especially considering how well the N1 with ColorOS performs in the other display tests.
