Saturday, September 21, 2013

Who knows completely about pixel per inch and dots per inch?

gaming monitor ppi
 on HTC One Mini leaked in black, aimed at Q3
gaming monitor ppi image



samar


Is a mobile device having 300 pixel per inch is equal to a printed photo having 300 dots per inch
i mean in terms of a human eye able to recognize individual pixel or dot and the smoothness of the display having 300 ppi and smoothness of the photo having 300 dpi are equal ?



Answer
pixels per inch are well defined. For a display, usually that means 3 elements per pixel, one for each of the 3 colors.

Dots per inch are pretty vague, specially for printers and cameras. Printers promise numbers like 1200 dots per inch, but how a "dot" is defined in a pretty vague way. Of course the manufacturer's marketing department adjusts the numbers to make the printer look more favorable.

I also know that cameras play games with the numbers also. for example, a 9 M pixel camera actually has 3 M of each of the 3 main colors, so this would really rate as a 3 M pixel for a display.

Bottom line, the numbers don't mean much. You have to look at comparative reviews in places like Consumer Reports.

wikipedis:
DPI measurement in printing

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; 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.

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. The range of DPI supported by a printer is most dependent on the print head technology it uses. A dot matrix printer, for example, applies ink via tiny rods striking an ink ribbon, and has a relatively low resolution, typically in the range of 60 to 90 DPI. An inkjet printer sprays ink through tiny nozzles, and is typically capable of 300-600 DPI. A laser printer applies toner through a controlled electrostatic charge, and may be in the range of 600 to 1,800 DPI.

The DPI measurement of a printer often needs to be considerably higher than the pixels per inch (PPI) measurement of a video display in order to produce similar-quality output. This is due to the limited range of colours for each dot typically available on a printer. At each dot position, the simplest type of colour printer can print no dot, or a dot consisting of a fixed volume of ink in each of four colour channels (typically CMYK with cyan, magenta, yellow and black ink) or 24 = 16 colours on laser, wax and most inkjet printers, higher end inkjet printers can offer 5, 6 or 7 ink colours giving 32, 64 or 128 tones available per dot location. Contrast this to a standard sRGB monitor where each pixel produces 256 intensities of light in each of three channels (RGB) to additively create 2563 = 16,777,216 colours. The number of unique colours for a printed CMYK dot from this simplest type of inkjet printer is only 8 since no coloured ink is visible when printed on black and black is used instead of CMY

what's the relationship between the pixel resolution and the actual size (in inches) of the screen?




Clueless


say, the physical screen size of my display is 5.75in x 7.75in. Why design at 1024 x 768ppi, if that equals 14.25in x 10.7in?
i understand that the pixel is a dot, not a measurement but, I don't understand the relationship between the two. why not design at 414px x 558px? thank you in advance!



Answer
The difference is the ppi (pixels per inch) of the screen. A monitor (or digital camera likewise) labeled as High Definition, for example, merely means it has a higher ppi. Here are some other examples as to why:
1. A gamer wants a mobile laptop that displays his games with high precision. He may go for a laptop with a small screen to make it lighter, but with high definition. A ppi of about 160 would be HD. If his screen is 11 inches wide, then it'd be about 1760 pixels wide.
2. Let's say a starting-up businessman wants a large screen for his desktop computer, but doesn't have much money. He could buy a large 32 inch monitor, with a lower ppi to save money.

The reason that resolutions come in standards has to do with computer architecture. Computers are built on powers of 2 (2, 4, 8, 16, 32, etc). Monitor width often follows in suit. e.g. 1024 (a very common screen size) is 2 to the tenth power. The reason 768 pixels high is often the height associated to 1024 is to keep what's called the aspect ratio (the ratio between the width and the height of the screen. In this case it is 4 to 3.) The actual math and figuring on ratios, ppi, and sizes is complicated and out of the scope for a quick and sufficient answer. Check my sources if you want to know more.




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