The first time you switch on an iPhone 6, you will be amazed at how clear the display is. It looks even higher definition than the iPhone 5s which is a pretty nice display itself. So, given that the screen of the iPhone 6 looks so much better than the iPhone 5s, I wondered what was different and ran into the lab for a quick capture of the iPhone 6 screen to see if any of the pixels had changed in size over the last little while.
With each iteration of the iPhone, Apple improves the screens to make them look substantially better, but what surprised me was that the resolution of the Retina Display, at least for the iPhone 4s, 5s, 5c and 6 is identical. I had previously measured and calculated the pixel size of the retina display and for the standard iPhone 6, the pixel size is ~326 PPI. The same exact size…
So, why does this display look so good? It turns out that what is different, like the iPhone 5 vs. the iPhone 4 is the proximity of the pixels to the glass in the iPhone 6 compared with the iPhone 5. With the iPhone 6, the pixels appear to be almost one with the glass. When the iPhone 5 came out, Apple bonded the display to the glass in an effort to get the pixels closer to the surface and Apple has appeared to make the pixels in the 6 even closer still. Some of what we are seeing with the iPhone 6 may be a polarizing filter underneath the glass, but even so, the glass appears thinner and required less focus distance adjustment to get from the surface of the glass to the pixel on another microscope. I don’t know what that precise distance is in microns between the surface of the glass and the pixels, but it was a shorter distance as judged by rotation of the focus knob in the iPhone 6 vs. the iPhone 5. What this accomplishes is making the display appear to be higher resolution. The blacks are blacker, contrast is higher and colors are more vibrant, even with the same OS.
Each display was imaged with the same settings on a stereomicroscope and a Canon 1D Mk III camera was used for imaging. Magnification was held constant in all captures. I used a Zeiss microscope with Zeiss 25x Plan APO lens to qualitatively measure the distance by focus knob rotation from the surface of the glass to the pixels.
I did find it interesting that Apple went with a different geometry to the subpixels in the iPhone 6. This is a geometry that has been used for Apple Cinema Displays going back to at least 2007 as well as on the iPad a couple years ago. What this does in terms of image appearance, I am not sure. It could simply be different manufacturing approaches or there may be a psychophysical difference between sub pixel geometries… I don’t know, but would love to hear from an LCD engineer on their thoughts here.
Interestingly, the iPhone 5 series of displays appear to have more texture in the sub pixels than on the iPhone 4 Retina Displays.
The image at the top was made with the following camera/settings:
Camera: Canon Powershot S100
Focal Length: 8.31