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What is Retina Display?

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Now everyone is talking about Retina display, worrying about the fact that they can not appear in the Mac, and looking forward to their appearance in the iPad 3 . There is an idea expressed by the developer Bjango Mark Edwards (Marc Edwards) on Twitter: “The number of pixels in the Retina 27-inch display with a Thunderbolt is 5120 × 2880 = 14,745,600 pixels. With a resolution of 4K: 4096 × 2160 = 8,847,360 pixels. Retina in the iPad 3: 2048 × 1536 = 3,145,728 pixels. ” The calculations make us think – that could mean the appearance of the display in the Retina Mac? If Edwards is right – is it in the display with the Retina and Thunderbolt is really almost 15 megapixels?

Maybe it’s just marketing?

What is generally meant by the term “Retina Display”? His thought of Apple, giving the following definition:

“The density of the Retina display pixels is so high that the human eye can not distinguish individual pixels.”

Definition makes sense and is a deliberate marketing ploy, but it?

In fact, this technology not only uses Apple. Screens with a high density of pixels per inch are beginning to appear in other devices – for example, the Android-tablet from Asus. Accurate term Retina display can only belong to Apple, but the benefits of high-resolution screens can not belong. Since this is a new trend for the industry as a whole, need a lot to try to shake off “the marketing dust” and try to objectively look at the technology.

Definition of Retina Display

That phrase could mean that the individual pixels on the screen are indistinguishable? Of course, the output of the iPhone 4 Retina display and the first was a big leap forward in increasing the resolution: it has grown from 320 to 480 × 960 × 640 (ie, with 163 pixels per inch to 326 pixels per inch (MHP)). Thus, people understand that a distinctive feature of the display Retina – a density of 326 IPA, IPA or 300. The last number is the generally accepted empirical baseline in the printing industry for a “photo-permission.”

But it’s not that simple.

Look at the text, printed in small type, with the arm’s length. Notice how difficult it is to read. Now approach the text-to-face and look at it from a distance of several inches from your nose. Notice how much easier it is now read it. It is becoming clear that the definition of the term Apple Retina Display as “indistinguishable from the display pixel” requires clarification – what exactly should be the distance from the screen to the user’s eyes for each device. There is a difference – iMac is on the table, MacBook – on a desk / lap, and so on, iPhone, we hold in our hands, each of us – at different distances from the eye.

So, what should be the size of a small pixel, so it can be regarded as invisible? It starts with math (or more precisely, the geometry) – we need to think about what angle we look at the screen.

Viewing angle in the diagram (angle a) – is the angle that depends on the inter-pixel distance (s). At this distance decreases as the angle decreases. Similarly, the size of an object depends on the distance from which it is considered – the viewing angle will vary depending on changes in object distance from the observer’s eye. The objects of larger size are clearly visible, and at extreme angles. The size of the image on the retina is inextricably linked to the size of the object and the distance to it, and is calculated as follows:

As it turns out – viewing angle is too small to see? The average person has 20/20 vision – it is historically determined by the ability to read letters on a standard eye examination table at an angle of 5 arc minutes (1 minute of arc, arkminuta – is 1/60-taya some degree). What does this mean in terms of pixels? Some of the smaller fonts are Tinyfont, created by Ken Perlin (Ken Perlin), and Tiny by Matthew Welch (Matthew Welch), and the height of the letters is only 5 pixels (with descenders in Tiny). This means that the smallest corner of your eyes for an average of one minute of arc. In fact, a arkminuta is generally accepted in the scientific world to the resolution limit of the retina of a typical human eye.

Retina displays in the current Apple Products

You can continue the calculation – to take some of the typical viewing distance for different devices, Apple, combine them with screen sizes and resolutions, and to calculate how much the display corresponds to the definition of Retina, above.

Google kindly provides a table with details on how these data are calculated. Just for the sake of comparison, let’s take a couple of “not apple” devices – 50-inch TV, which will look from a distance of six feet (about 1.8 meters) and play BluRay discs and DVD; and tablet Asus Transformer Prime Android with a resolution of the display 1920 × 1200.

The table shows the amazing things: first, it is clear that the definition of Apple’s Retina-screen, quite closely related to the mathematical definition given above. IPhone screen 4, which is usually watching from a distance of 11 inches (28 centimeters), offers features that are very close to the threshold of the Retina – hence, the correct method of calculation.

Second, the calculation is repeated our earlier conclusion that the double resolution iPad (2048 × 1536) it is correlated with the characteristics of Retina. Even if you use the tablet at a distance of 16 inches (40 centimeters) from the eye, the figures obtained are very close. As well as in tablet Asus – its display can also be considered Retina.

The calculations also show that displays many of today’s Mac is much closer to that of Retina, than might appear at first glance. Display 27-inch iMac at a distance of 28 inches (70 cm), 17-inch MacBook Pro at a distance of 26 inches from the eye (66 cm) and a screen 11-inch MacBook Air with a distance of 22 inches (56 cm) – all of these screens have pixels are small enough to be on the verge of invisibility.

In addition, the iPhone display with 480 × 320 looks much worse compared to other products created by Apple to date (its density is only 53% of the density of the Retina-pixel display). Even the resolution of iPad (1024 × 768), which many are dissatisfied, in the calculations gives the best indicator – 61%. Analysis of the “bad” display Mac (24-inch screen iMac at a distance of 28 inches) shows that the value of its pixels by a third over the same threshold of invisibility.

Finally, the calculations make it clear why the BluRay picture looks so good. On the big TV at a small distance from the screen (diagonal – 50 inches, removing – 15 cm) image of 1080p displays 92% level of Retina – despite the fact that the DVD format shows only 36%.

Here we must consider two very important points:

First, in order to reach or even exceed the desired threshold of invisibility pixel display Retina, Apple does not need to double the resolution of most of its displays. Far from it – enough to increase the pixel density 27-inch Thunderbolt Display with 2560 × 1440 to about 2912 × 1638.

The second point is that people should understand that they should not deceive ourselves about the fact that Retina-Display for Mac will be much better than existing proposals. The output iPhone 4 was a huge step forward after the release of iPhone 3GS, mainly because the screen was pretty miserable 3GS (by today’s standards). The current Mac models have much better screens, so they will need not strong improvements.


- Retina-display is not just an attractive marketing concept;

- The determination, is the Retina display or not, must take into account the distance to the screen;

- If to improve the display characteristics of the Retina Mac, then the changes will be much less noticeable than the improvement of the iPhone 4 display compared with the display of iPhone 3GS.

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