What is DPI? Not everyone knows the answer to this question. And this article will help.
DPI (Dots Per Inch) - the number of dots per inch. It is used to determine the resolution of the screen. But some confuse the DPI of a monitor with PPI (Pixels Per Inch). The latter indicates the number of pixels per inch.
For example: for a square of one inch, you need to display a picture with a resolution of 96 dpi, where each side will contain 96 pixels; for printing on paper, 600 pixels per side are required when the DPI resolution is 600.
For comparison: they talk about the high resolution of photographs (for example, 3000x1500, where the image width in pixels is 3000 and the height is 1500). You can extract from this that the picture is large enough when viewed on the screen. And what will happen if you print it? For this, there is the term DPI, which defines the number of dots that the printer will apply per inch of paper.
Historical remark: DPI of the monitor
Old VGA monitors of the early 80s had DPIs from 70 to 74, when similar Apple products (Macintosh monitors) had a resolution of 72 DPI, in which one pixel corresponded to a real typographic figure of 1/72 inch.
Studies have shown that the distance of the human eye to the monitor screen is three times greater than the distance to paper media (newspaper, book), thus the image on the monitor is noticeably smaller. For comfortable work and compliance with the actual image size, it was decided to programmatically set the resolution to 96 DPI. But in reality, the resolution of the monitors was 70 - 74 DPI.
Only later, IBM released a monitor with a resolution of 96 DPI. Immediately after that, software support was made at 120 DPI. This negated binding to the actual typographic metric of 72 DPI.
What is DPI: changing the resolution of a monitor
First of all, changing DPI affects the correct display of elements and images on the screen, this is not a way to increase or decrease the size of fonts and icons. If the text on the screen with the correct resolution looks small, then you should change its size, and not get into the resolution settings of the monitor.
Another feature, even the danger, of an incorrect DPI setting is hidden in the visual difference in screen sizes and print results. In the field of software and software development, an incorrectly set DPI value can lead to unreadability of the interface or text: a too large indicator (large interface elements) will force the developer to reduce the working area (text), which is unacceptable on screens with correctly set DPI.
There are several recommendations for developers and custom software lovers. It is better to create programs or presentations according to templates, which eliminates the mismatch of DPI indicators. Any such interface will be correctly displayed on any monitors with different resolution. When using a raster image, it is worth preparing two drawings with different DPI indicators (96 and 120). And at different monitor resolutions, the corresponding picture will be selected.
What is DPI: output
The modern user interface of programs and operating systems is focused on the resolution of the monitor in both 96 DPI and 120, which is a big plus. But some video card and monitor drivers allow you to set personalized text values, dialog boxes, and other little things, which will lead to incorrect display of the picture.
To complete the picture, let us explain what DPI is with a simple example. The physical dimensions of the monitor remain unchanged in any situation, and when you change the resolution from 1024 × 768 to 1280 × 1024, the DPI also changes. The screen visually shrinks and a lot of free space appears, but all the elements of the desktop and the font remain the same. The pixels themselves have decreased to fit on the same screen area, at the same size.