Display And Audio
Modern smartphones are really just miniature computers that also do telephony. Rapid advances in computational power are driving phones to adopt larger screens, just they have for every other computing form factor. Either because of denial or stubbornness, it took Apple a bit longer to accept this trend, finally giving its users access to more screen space with the iPhone 6.
After such a radical change, it's no surprise that Apple made no significant screen changes for this generation. The iPhone 6s still uses a 4.7-inch IPS panel with an odd, greater than 720p, 1334x750 resolution, giving it a sufficient 326 PPI pixel density. The larger 6s Plus comes with a 5.5-inch 1080p IPS panel with a 401 PPI density. While most flagship phablets are shipping with QHD (2560x1440) screens these days, the iPhone 6s Plus' 1080p panel is still very sharp. QHD is only really necessary for AMOLED panels (due to having fewer red and blue subpixels than RGB stripe LCD panels), virtual reality applications (because the screen is closer to your eyes), and for people who augmented their genetic code with eagle DNA.
Last year, Apple adopted two technologies for its larger Retina HD Displays that carry over to this generation: photo-aligned crystals and dual-domain pixels. Using light and a photoresist layer to achieve better crystal alignment improves the display's overall performance, including a lower black level and better contrast ratio. Dual-domain pixels, like the name implies, split each pixel into two domains or subpixels that have a slightly different crystal orientation. This technique improves viewing angles: While shifting your view, the pixels oriented away from you become dimmer, but the complementary subpixel oriented towards you gets brighter, partially compensating for that color's brightness reduction.
For our display measurements, we're using SpectraCal's CalMAN software and SpectraCal C6 colorimeter. All of the charts below with a gray background were generated in CalMAN v5 Ultimate. If you would like to learn more about our display testing procedure, or gain a better understanding of how these measurements affect visual quality, please read our article about how we test mobile displays.
The iPhone 6s achieves a max brightness just shy of 550 nits, in between the 6s Plus and iPhone 6. In fact, the last three generations of iPhones all fall between 500 and 600 nits, bright enough to handle nearly every situation except direct sunlight. The only phones we've seen break the 600 nit barrier use Samsung's SAMOLED panels, but only in the Auto overdrive mode. The only other phone we've tested that gets close to 600 nits is the OnePlus 2.
The use of photo-aligned crystals help give the iPhone's displays very good black levels, although not as good as the IPS screens in both the OnePlus 2 and LG G4 (we asked LG if the G4's display also uses photo-aligned crystals, but received no response). Of course none of the IPS screens can match the perfect blacks produced by the AMOLED panels in Samsung's Galaxy S6 devices.
Most flagship phones have an average gamma near the ideal value of 2.2, and the new iPhones are no different. Gamma also varies little with luminance, ensuring good dynamic range and improved color accuracy regardless of display brightness.
All iPhones dating back to the 5s hover right around 7300 K (our 6 Plus being a slight deviation), a slightly cooler color temperature that gives a pure white screen a noticeable, but faint, blue tint. It's obvious that Apple is deliberately targeting this color temperature, but why? Is it the result of market research showing a clear preference for this setting, or maybe it's the value used on Jony Ive's desktop monitor? Whatever the reason, if you've used an iPhone in the past couple of years, the new iPhones' screens will look familiar.
Like most IPS phone displays, the new iPhones show an increasing disparity between red and blue approaching 100 percent luminance. This is what gives the screens their cooler temperature profiles and slight blue cast. It also helps boost the iPhones' max brightness: Because of the blue LEDs used in the backlight, the screen will naturally emit more blue light than red. The only way to achieve a proper RGB balance is to partially close the blue subpixels, limiting max brightness.
The new iPhones do reasonably well with grayscale accuracy, although not as well as Motorola's Moto X Pure Edition or Samsung's Galaxy S6 devices when using the Basic display mode. For luminance values less than about 40 percent, ΔE2000 error remains below three, which is considered good. Grayscale error reaches a maximum of around 5 near 100 percent luminance, the cutoff where error is noticeable but generally acceptable.
Apple continues to target the sRGB color space with its displays, avoiding the overly saturated, inaccurate colors that result from using wide-gamut displays with no software based color management.
Both new iPhones perform the same in the color saturation sweep, with no major problems. Shades of blue are a bit too saturated, though, just missing the target boxes. We can also see how the cooler color temperature pulls the nearby secondary colors, magenta and cyan, towards blue.
While neither iPhone performs system-wide color compression, we did notice that Apple's native Photos app does apply color compression, which is a little surprising. So if you desire better color accuracy when reviewing photos on an iOS device (well, as accurate as you can get on an sRGB screen), you'll need to use a third-party app.
When it comes to color accuracy, both the iPhone 6s and 6s Plus show decent improvements over the previous generation. For the tested colors, ΔE2000 error hovers around three or below, with shades of green being the most accurate, ensuring most of the error will go unnoticed. Just like we saw with grayscale error, however, both Motorola and Samsung (in Basic mode at least) are doing a better job than Apple with display calibration.
Full Size Images: [Color Palette: iPhone 6s], [Color Palette: iPhone 6s Plus]
The color palette above shows the target color on the bottom versus the displayed color on the top and is a nice way of visualizing the color error discussed above [note: the color accuracy of your screen will affect the actual colors you see]. A faint blue tint is visible on the gray shades, but most colors are very close to the target values.
Our display testing found no obvious issues with the iPhone 6s and 6s Plus. The displays are very similar to the previous models, but with slightly improved color accuracy. While Apple cannot claim to have the best smartphone screens, it still sets a performance standard many OEMs have yet to reach.
Audio Performance
Apple continues its longstanding relationship with Cirrus Logic for Audio ICs. Because Apple applies its own numbering system to the chips, we cannot determine their exact specifications. However, the single 338S00105 audio codec likely handles AD/DA conversion, while the two 338S1285 audio ICs probably operate as separate amplifiers for the external speaker and headphones/earpiece.
Also keeping with iPhone tradition, there's only a single, downward-firing speaker for music and audio. While not as good as having it on the front, we find this speaker location preferable to rear-mounted speakers, since there's less likelihood of your hand blocking the speaker when holding the phone or the sound getting muffled when it's sitting on a table.
Listening to a variety of music, ranging from Metallica to Daft Punk, through the external speakers of the iPhone 5s, 6, and 6s shows a clear progression in quality from old to new. Music from the 5s sounds muddy and flat, with subtle background sounds getting lost in the noise. The iPhone 6's sound quality is vastly improved, but still sounds a bit tinny. The 6 also seems to emphasize the strongest sound (usually vocals for music), while suppressing background tones.
The quality improvement from the 6 to the 6s is smaller than the jump from the 5s to the 6, but it's still quite noticeable. Sound from the iPhone 6s is fuller, shedding some of the tinniness of the prior model. Music is also clearer, allowing you to better isolate individual instruments and sounds in the background. Bass output is similar, but drums sound a bit tighter on the 6s.
The new iPhone also delivers more balanced sound output, eliminating the iPhone 6's tendency to exaggerate vocals or the loudest instrument. Depending on personal preferences and what's playing, this change can be either good or bad. The max volume is sufficiently loud to be heard across the room and is essentially the same as the iPhone 6, but louder than the 5s.
Headphone output sounds excellent, with no discernible difference in audio quality between the iPhone 6 and 6s. The iPhone continues to be our reference device for headphone sound quality, although several devices, such as the LG G4 and Sony's Xperia line, now match the iPhone's listening experience.
