Retina Display is a brand name used by Apple for the IPS LCD and OLED series with higher pixel density than traditional Apple screens. Apple applied to register the term “retina” as a brand concerning computers and mobile devices with the united states patent and trademark office. Canadian intellectual property office. Applications were approved in 2012 and 2014, respectively. The Canadian app services cited the 2010 request in jamaica.
When an Apple product has a Retina screen, each user interfaces item doubles in width and height to compensate for smaller pixels. Apple calls this HiDPI mode. In simpler words, it is one logical pixel = four physical pixels.
The advantage of this equation is that the CPU “sees” a small part of the data. And calculates the relative positions of each item. The GRAPHICS unit displays these elements with high-quality assets to make more precise and transparent outputs.
In addition, retina screens intend to make the text and images displayed so clear that pixels are not visible to the naked eye or at viewing distance. It allows displays to compete with smooth curves, sharpness of printed text. And instant photographic prints.
Apple Retina screens are not an absolute standard for screen clarity but vary depending on the screen size on the device. And at what distance the user can usually see. For example, users on smaller devices can view the screen from a space closer to their eyes.
This is because the screens have more pixels per inch, while in larger machines with larger screens where the user sees the screen away, the screen uses less PPI value.
The logic of Retina Display
When introducing the iPhone 4, Steve Jobs said the number of pixels required for a retina screen is about 300 PPI for a device that carries 10 to 12 inches of the eye. One way to express this as a unit is the pixels per degree (PPD) that consider both the screen resolution. And the distance from which the device remains displayed.
Based on the projected 300 job count, the retina’s minimum PPD screen of 57 PPD. 57 PPD means that a long, thin triangle with a height equal to viewing distance. And a one-degree overhead angle will have a base on the device’s screen covering 57 pixels. The quality of the display
Retina Display (from phone screens to large projectors) can be described using this global, independent-sized parameter. Note that the PPD parameter is not a core parameter for the display itself, unlike the absolute pixel resolution (e.g., 1920 × 1080 pixels) or the relative pixel density (e.g., 401 pixels per inch), but depends on the distance between the screen and the screen eye. It is because a person (or device lens) watches the screen.
The first smartphone to follow the iPhone 4 charging with a similar pixel-density screen was the Nokia E6, powered by the Symbian Anna system. With a resolution of 640 × 480 with a 62.5mm screen size. However, it was an isolated platform case. As all other Symbian-based devices had larger screens with less resolution.
Some of Symbian’s older smartphones, including the Nokia N80 and N90, feature a 2.1-inch 259p-per-inch display, which was one of the sharpest phones of the time. The first Android smartphone on the same screen – Meizu M9 was launched a few months later. At the beginning of 2011. In October of the same year, the Galaxy Nexus was announced, with a screen with better resolution.
By 2013 primary 300+ was found on medium-range phones such as motorcycles and G bikes.  in From 2013 to 2014, many significant devices such as the Samsung Galaxy S4 and HTC One (M8) had 1,080p (FHD) screens about 5 inches to 400+ PPI that exceeded the retina density of the iPhone 5. The second major redesign of the iPhone.
The iPhone 6, with 1,334 × 750 on a 4.7-inch screen, while competitors such as the Samsung Galaxy S6 have a 2,560-× QHD display 1440, nearly four times the number of pixels found in the iPhone 6, giving the S6 577 PPI roughly twice as many as the iPhone 6’s 326 PPI.