What is the new iPad Retina display?

Being Retina display does not depend only on the PPI. It also depends on the viewing distance.

Using the formula A = 2tan-1 (H/2d) at 15 inches (2.54 cm) away qualifies for a retina display.

The eyes cannot discern the pixels at the distance, which is the essence of retina display.

 

How is retina's screen defined? Why is the resolution of a new iPad screen called a Retina screen. Next, let's have a deeper understanding.

Why did Steve propose a 300ppi?

 

Some friends set "Resolution PPI" to determine the Retina screen standard, and the connection between PPI and Retina screen started with the release of wsdc2010 and iphone4, at that time, Steve Jobs said, "When the handheld device is 10-12 inches away from the human eye, the 300ppi (the data proposed by the instructor is open to question because it will be detailed below) is the limit of human vision (to the greatest extent) ". This sentence has a premise of "10-12". It is obvious that Steve Jobs did not give a Retina screen definition based on "Resolution PPI.

But later we all remembered the PPI, and some of our friends took the PPI as the Retina screen standard.

 

How is the formula α = 2tan-1 (H/2d) obtained?

 

Scientific Analysis of Retina screen criteria

 

α = 2tan-1 (H/2d) is based on the study of human vision. α represents the angle of view, theoretically, the minimum angle of view that can be recognized by human eyes is 0.78 arc discrimination (1 arc discrimination = 1/60 degrees ). Based on the theoretical data and the impact of ambient light on image quality, the minimum angle of human eyes is usually 1 arc discrimination (1/60 degrees ).

In addition, it should be noted that the 1-arc discrimination data is mainly based on the statistical samples of visual acuity 20/20 (equivalent to the well-known 1.0), and the visual acuity is extraordinary (such as 2.0 of visual acuity) individuals will undoubtedly have better visual capabilities, and the minimum angle of view for identifying external things will be smaller.