Test Results: Display Measurements
Brightness (also known 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 both minimum and maximum values.
Max brightness for the iPhone 6 Plus is slightly higher than the 5s at 500 nits. The iPhone 6 is even brighter, making it easier to see in direct sunlight.
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.
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. It's important to note that AMOLED displays will always measure a black level of zero, since their pixels simply turn off to render black.
The new Retina HD screen improves upon the already good black level of the iPhone 5s. The smaller screen in the iPhone 6 shows slightly better results than the 6 Plus.
The SAMOLED screens in the Note 3 and Note 4 are able to achieve a true black since the organic LEDs are switched off and not emitting any light.
Contrast ratio is the difference between a full white pattern and a full black pattern. Due to their zero reading on the black level tests, AMOLED displays are said to have an infinite contrast ratio.
Due to SAMOLED's ability to represent a zero black level, the two Galaxy Notes have a mathematically infinite contrast ratio. Unable to divide by zero, the iPhone 6 settles for a more tangible, but still impressive value better than the HTC One (M8) and significantly higher than the iPhone 5s. Once again we see the screen in the 6 Plus fall just shy of the mark set by its smaller sibling.
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 optimally 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.
Apple's factory screen calibration routine gets very close to the optimal gamma value, essentially equaling the performance of the iPhone 5s. The screen in the HTC One (M8) is the only one to deviate from the ideal by an appreciable amount.
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 are above the ideal 6500K value. The Galaxy Note 4 hits closest to the target value, followed by the iPhone 6. The 6 Plus deviates a bit further from the mark.
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 the optimal reading for viewing the vast majority of digital consumer content. A lower reading is typically accompanied by an overly red or yellow image, and a higher reading is usually too blue/green.
The SAMOLED screen in the Note 4 displays the widest color gamut, exceeding 100% of the sRGB color space. The iPhone 6 covers nearly the whole sRGB gamut, yielding a slight improvement over the 5s.