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Mi MIX 2

[Discussion] [Device Team] [Tech Class] Chapter 39 : All about Pixel Density & DPI

2017-11-25 17:13:19

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Before starting this topic, first, we have to know what Pixel density is.
Pixel density (PPI) Refers to the concentration of pixels on a particular display, measured in pixels per inch (PPI). Pixel density is calculated by dividing the diagonal pixel resolution of a display by its diagonal size.

Let’s discuss in brief,
  • Pixels are the small dots that make up your computer, TV, and phone screen. Digital displays are comprised of pixels. Pixels work together by switching colors extremely fast to create a persistent and smooth viewing experience for the user.
  • Learning everything there is to know about pixels is a challenge especially as screen technology changes more rapidly. But there are some basic terms relating to these tiny dots that make up so much of our world that are helpful to know.

Pixel density (8).jpg

What is the pixel density?
  • Pixels per inch (PPI) or pixels per centimeter (PPCM) are measurements of the pixel density (resolution) of an electronic image device, such as a computer monitor or television display, or image digitizing devices such as a camera or image scanner.
  • Horizontal and vertical densities are usually the same, as most devices have square pixels, but differ on devices that have non-square pixels.
  • PPI can also describe the resolution, in pixels, of an image file. A 100×100 pixel image printed in a 1-inch square has a resolution of 100 pixels per inch. Used this way, the measurement is meaningful when printing an image. It has become commonplace to refer to PPI as DPI, even though PPI refers to input resolution.

Resolution vs Pixel density
  • Usually, displays are measured in size(in centimeters and inches). Here we only measure the diagonal size and not the horizontal or vertical size of the screen. There is also another important property of display which is the resolution.
  • Resolution refers to the size of the display in terms of pixels. E.g. Resolution of 800×600 pixels means that the three are 800 pixels horizontally and 600 pixels vertically. So, therefore, there are a total of 480000 pixels in the display.

Pixel Density
  • Many of us are not aware of the importance of Pixel Density in displays. It is the thing which describes the sharpness and clarity. Pixel Density is usually measured in PPI (Pixels Per Inch) which refers to a number of pixels present per inch on the display.
  • Higher the pixel density higher is the sharpness of the content. Pixel Density is calculated based on the resolution and size of the display.

Pixel density (4).jpg

How to calculate Pixel density?

You can calculate PPI in multiple ways. The most common one is to calculate it from the diagonal screen size (in inches or cm) and the number of pixels along the vertical and horizontal edge of the display.
  • First, you need to calculate the number of pixels that fit on the diagonal:
d? = v(w² + h²)
  • W is the number of pixels along the horizontal, and
  • H is the number of pixels along the vertical.

Then, you can calculate the PPI as the ratio between the number of pixels along the diagonal and the diagonal screen size:
PPI = d?/d?
  • d? is the diagonal screen size in inches.

What is DPI (Display per inch)?
  • The original DPI term, as used with a digital photo, goes way back to the days when a digital image was printed to a printer using a 1 to 1 ratio (1 pixel = 1 printer dot).
  • DPI is used to describe the resolution number of dots per inch in a digital print and the printing resolution of a hard copy print dot gain, which is the increase in the size of the halftone dots during printing. This is caused by the spreading of ink on the surface of the media.
Pixel density (2).jpg
Up to a point, printers with higher DPI produce clearer and more detailed output. A printer does not necessarily have a single DPI measurement; it is dependent on print mode, which is usually influenced by driver settings.

Difference between Pixels and DPI (Dots per Inch)?
  • Pixel is used to describe the number of discrete points that can be captured by digital cameras, and because most cameras can actually recognize millions of points, the term Megapixel is used to shorten the number of zeros needed.
  • Pixel indicates only a point on a grid, not the size of the point. Instead, Pixels create a pattern based on the scale of the device being used.
Pixel density (7).jpg
For Printers and scanners, the individual points of color are often called 'dots' rather than pixels, but the concept remains the same as the stadium.
  • Because the output of a printer is a paper which is usually measured in inches, the term DPI or Dots per Inch is used to communicate the scale or physical size of each pixel.
The scanner performs this function in reverse, by recognizing the color at a specific row and column on the item being scanned. The scanner or digital camera actually records a file of information indicating what color appeared at what position in the picture.

What Is Retina Display?
  • Retina Display gets its name from Apple's claim that screens made with the technology are so sharp and high quality that it's impossible for the human eye to distinguish individual pixels.
  • Retina Display smoothest the jagged edges of the pixels that make up images on screens.
  • The benefits of the technology are visible in many uses, but especially for displaying text, where curved font edges are substantially smoother than on previous display technologies.
Pixel density (1).jpg
Retina Display's image quality derives from a number of factors:
  • A high density of the pixels that make up the device's screen
  • Higher contrast ratio than previous models to create brighter whites and deeper blacks
  • In-Plane Switching (IPS) technology to improve the angles from which the screen can be viewed
  • Chemically treated glass over the screen and LED backlighting to improve the quality of the image.

So, bottom line, a high-resolution photo is an image with high-quality pixels, saved in either a non-lossy file format or a low compression (high quality) JPEG, that can supply the desired PPI (usually 300) for the intended print size.

A Tech Class Recap
Class 15:All CPU Cores
Class 17:All About RAM
Class 28:All About IP(Ingress Protection)Ratings
Class 32:MIMO Technology Explained
Class 33: All About Gi-Fi
Class 34: All you need to know about ADB
Class 35: All about Factory reset
Class 36: More about on Internet Protocol (IP).
Class 37: Android Voice Recognition - In Detail
Class 38: Mobile Touch panel – An Android Input

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2017-11-25 17:13:19
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