AnandTech’s Anand Lai Shimpi and Brian Klug thoroughly reviewed the iPhone 4S and I’ll focus on the results for the 3.5-inch IPS LCD.
First, white point. The iPhone 4S has a 7000K white point compared to 6250K on the iPhone 4. A higher white point will make the white on the display bluish. White point is subjective and can depend on geographic locations. For instance, a warmer white point is preferred in colder places and vice versa.
Related to white point color temperature is white point fluctuation, which is more pronounced on the iPhone 4S depending on different brightness levels compared to the iPhone 4. This doesn’t affect users, like me, who turn off automatic brightness control, but can be considered evidence that display quality is not quite up to par on the iPhone 4S. On the other hand, the iPhone 4 exhibits extremely stable white points at different brightness levels.
Second, white brightness levels. The iPhone 4S and iPhone 4 are almost identical with the iPhone 4S showing slightly lower levels of brightness starting around the 50% level. The iPhone 4S has an overall brightness of 569 nits. The iPhone 4 beats it with 583 nits, but the brightest is the Motorola Droid X2 with 697 nits.
Third, black levels. The iPhone 4S continues to be much better in terms of black levels than the rest of the competition through roughly the 65% brightness level with one exception: The SLCD used in the HTC Sensation has an incredible slope with blacks actually getting darker as the display gets brighter! Unfortunately, the blacks are not as black on the iPhone 4S as they are on the iPhone 4 at every brightness level. Overall black levels for the iPhone 4S is 0.79 nits while the iPhone 4 beats it with 0.68 nits. The smartphone with the darkest blacks on a LCD is the Motorola Droid 2 with 0.25 nits followed closely by the original Droid with 0.30 nits.
Fourth, contrast. With slightly lower levels of white brightness and blacks that are less deep, it’s not surprising to see a weaker contrast on the iPhone 4S. With a 720:1 contrast ratio the iPhone 4S falls short of the 857:1 contrast ratio on the iPhone 4. The best is the Motorola Droid 2 with a contrast ratio of 1773:1 followed by the original Droid at 1418:1.
The LCD with the brightest white levels, deepest blacks, and highest contrast were all manufactured by LG Display, who also supplies the 3.5-inch IPS LCD in both the iPhone 4 and the iPhone 4S. The slight degradation in white brightness levels, slightly washed out blacks, a white point that is less stable, and a lower contrast ratio is disappointing. I expect Apple to at least maintain the same level of display quality especially when the display is the focal point for the iPhone experience.
More demand means Apple will need to procure more displays and that generally means lower quality unless someone does something about it. Just like the aluminum unibody design that simplified the internal structure, reduced manufacturing steps, and enhanced robustness, Apple needs to work closely with LCD suppliers like LG Display to redesign the internal structure of the LCD so millions can be manufactured while maintaining a high level of quality.
There is a rumor that LG Display is not the only display supplier for the iPhone 4S and that may be one of the reasons for the slide in quality. Nonetheless, I expect Apple not only to maintain top notch quality levels on par with previous offerings but to improve them over time. Unfortunately, the iPhone 4S display quality falls below expectations.