Apple introduced not only the iPhone 6, but the iPhone 6 Plus at last week keynote. SDuring the presentation, it was noted that the screen Resolution “six” was bigger than the previous model 5S, which has 750 × 1334 pixels on a 4.7-inch screen. This model should replace the existing line of iPhones. But, apparently, that’s not the case. Bruce Wang decided to look more into it.

Let’s make the iPhone in size 5-6 inches, okay, let it be a happy medium 5.5 “. The essence of marketing ploy  is simple: customers can choose between a truly great iPad, or simply a big iPhone – the main thing that they were not looking at the device competitors.

The risk of this strategy is that the potential owners of the two devices – iPhone and iPad – may well decide that it is enough and one iPhone-phablet.

And here we have iPhone 6 Plus with a resolution of 401 ppi. Very strange number, at first glance – a mistake. But no, if you take the resolution of 1080 × 1920 pixels and converted to a diagonal 5.5 “, you get 400.52 ppi. That’s right, there is no error. But how then would the “real” resolution of the device be?

A little bit about the screen resolutions

Here we must make a slight digression and recall that in addition to the native resolution of the screen, in pixels, in iOS there is also a logical resolution of the screen, as measured in the so-called points (dots). Points and pixels are interconnected scaling factor (“retina”-factor).

For older models of iPhones, this factor is equal to unity, and the native resolution of 320 × 480 pixels correspond to the same logical resolution – 320 × 480 pixels, or 163 dpi (scaling factor of 1 ×).

Retina screen of the iPhone 4 was four times greater than the physical resolution – 640 × 960 pixels, or 326 ppi, but the logical display resolution is not changed, and still is 320 × 480 pixels, but now these points are drawn with double precision (scaling factor 2 ×).

iPhone 5 got new display sizes, but its definition remains the same – 640 × 1136 pixels with a diagonal physical 4 “give the same pixel density of 326 ppi, appropriate logic density 163 dpi (2 ×).

Finally, a new iPhone 6 display again increased to 750 × 1334 pixels, but its density is still equal to 326 ppi, and logical resolution is scaled with a constant factor of 2 ×, and is 375 × 667 pixels, or 163 dpi.

Why point so important? Because that’s what they are measured by the size of the interface elements on the screen. Button 44 height point will be the same size as the screen of the old iPhone 3G, and screen new “Six” – approximately 7 millimeters. The only difference is in the detail: in the second case, the button will be rendered at double precision (the same scaling factor).

Changing the logical density of the screen at points it changes the physical size of the interface elements. Fluctuations in the vicinity of 150-170 dpi hardly be noticeable to the eye. If the density becomes greater than 170 dpi, then the elements of the “shrink” button will be small, and they simply will not be able to get a finger. Conversely, if you reduce the logic density below 150 dpi, the entire interface will increase, as it was a display of 10-inch iPad, whose density is 132 dpi.

To summarize, increasing physical definition screen (ppi) makes sense only when you save the logical definition of the acceptable range (dpi), which should ideally be in the range of 150-170 dpi. Only in this case, the elements of the system interface and applications will retain their usual size.

 iPhone 6 Plus Resolution

So what can be the logical resolution of the display is 1080p with the physical definition 401 dpi? Here are a few possible scenarios.

1 If it is decided to use a scaling factor of 2 ×, then the logical screen size is 540 × 960 pixels, which is pretty good for fableta. But the problem is that the logic density of the screen – 200 dpi. The whole interface is compressed to such an extent that the device will not be able to use. Bad choice.

2 Let us now try scaling triple 3 ×. It brings to the screen density 134 dpi – bit much for the iPhone, but rather a “tablet” value. But the main problem is different: this screen will have a logical size of only 360 × 640 pixels, it is less than that of the younger models of the iPhone 6 – 375 × 667 pixels with zoom 2 ×. This is unacceptable, because it is stated that the iPhone 6 Plus should have more room for content compared to the iPhone 6.

3 If no 2 ×, or 3 × zoom does not work, then what? Some sources suggest that the fractional scaling like 2,5 × will be used – but this one looks completely alien.

4 A little research files Xcode reveals the truth. applying the theoretical resolution of the screen in 1242 × 2208 pixels with a triple-definition corresponding to the logical size of 414 × 736 pixels. And then the picture is compressed at the hardware level to the scale of the display 1080p. About this could not conceive of anybody. Even the venerable “epplovod” John Gruber, who guessed exactly resolution displays both iPhones.


However, this is exactly what is really going on. Let’s for a moment forget about the panel 1080p, and imagine that it is actually used for the iPhone 6 Plus display with a resolution of 1242 × physical 2208 pixels and a triple zoom. In this case, the logical screen size will be 414 × 736 pixels, and its density is 154 dpi – everything looks perfect! Well, the rest will take care of hardware compression to lower than anticipated panel of the screen. In this picture a little lost in the details, about 13%.

It is important to realize that hardware compression does not affect the physical dimensions of the interface elements on the screen of the phone. Status strip height of 20 points will be almost the same height and on the iPhone 6 and iPhone 6+. In terms of the size of the interface is much more similar to the transition from the iPhone 4 to the iPhone 5 than the difference between the iPad and iPad mini. Compression with scaling and reduction in size is not the same thing! Clearly the difference can be seen in the following picture.

What are the disadvantages of this approach? Will the image is noticeably blurry? And hey, they’ve just killed an exact match logic points to physical pixels! Farewell, line 1 pixel! ..



Well, in fact it may not be so terrible. Yes, such a solution is unique compromise, and it destroys the perfect licking interfaces “to the last pixel.” But we’re talking about the triple scaling factor! Any compression artifacts are so small that to the naked eye they still did not notice, so that instead of hunting for the pixels can focus on creating great design. Our favorite faithful customers which is hardly something to suspect. Pure magic!

Talk about a loss of accuracy

Now we know that the magic compression to work hard to fit all of these millions of pixels in a small space. (Yes this is Singapore!) Some pixels will inevitably be drawn accurately, and the time to remember our friend antialiasing. The main question is whether these blurred lines visible eye?

Let’s imagine that we draw a black line width of 1 pixel on the screen is not retinoic with initial coordinates X = 0; Y = 0,25. In the pixel lattice, this line takes two rows, each of which will be drawn in different shades of gray. If you draw the same line in the “double” of retinoic screen, it will already contain ½ completely black pixel and two more half-pixel gray. Now take the screen Retina HD triple clarity – all black pixels are already ⅔. On screens with high resolution pixel size of the lattice – about 0.06 millimeter. My eyes start to squint at the very thought of it.

But why use the  1080p display instead of the right one?

1 Thinking about money. Screens with a resolution of 1080p more accessible, it is more or less a standard resolution. Companies need to maintain margin and price of the iPhone 6 Plus is not too different from the iPhone 6 – c big screen, larger battery, better camera more expensive it is only $ 100. But in the long term sales of the iPhone 6 Plus take away market share from the iPad, and these also need to cover the losses.

2 Availability of relevant screens. It is possible that providers simply do not have time to make the right number of panels, jeopardizing the timely release of the iPhone 6 Plus is light.

In fact, such a solution – a very smart move and here’s why:

  • In the future, in a hypothetical iPhone 7 Plus,  will be able to use the original resolution 1242 × 2208 without any problems for developers.
  • A balance between the value of dpi and available screen size – 1080 physical pixels, but at the same time, much more than just 1080p.
  • Do not hurt profitability.
  • The use of commercially available panels allow the release iPhone 6 Plus in sufficient quantities to meet demand.

Summary conclusion: in a constant race “pixel” HD screens (ppi) the main problem is choosing the right zoom level to save logical resolution (dpi) within acceptable limits. For iPhone 6 Plus has chosen the exact triple scaling 462 ppi / dpi 154 pictures in 1242 × 2208 pixels. However, this picture is a hardware compressed to fit in the physical panel 1080 × 1920.

Even more short conclusion at the hardware level screwed up. We not only got a sapphire screen, but the resolution of the panel is worse than expected. However, at the program level – respect for the preservation of the original permit.

Developers: do not use the resolution of 1080 × 1920 for design under iPhone 6+. Use only 1242 × 2208

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