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All digital photos fundamentally consist of countless, interconnected pixels. These tiny pixels contain information about colour and brightness. When an image is captured, the camera’s image sensor stores individual detected pixels and projects a corresponding image.
The resolution indicates how detailed an image can be reproduced or how many pixels it consists of. Different minimum resolutions may be required for optimum image quality. In principle, the higher the resolution, the better the image quality. Thus, a photo with a low resolution can only be enlarged to a limited extent or not at all, without blurring or distorting the content. Consequently, the ideal resolution depends, among other things, on the intended use of the photos. Photo prints in various sizes require different resolutions than images that are only displayed on a computer. The print resolution is usually much higher than a screen resolution.
There are two possibilities to measure image resolution and to record it numerically. On the one hand, the absolute image resolution and on the other hand, the relative image resolution can be determined.
Absolute image resolution
The absolute image resolution shows the number of pixels based on their occurrence in rows and columns. It is calculated from the image width x image height and can have, for example, 685 x 390 pixels. This form of measurement is mainly used with screens or in television technology, since the absolute image resolution also corresponds to the image size. In digital photography, this information is converted into megapixels (MP). Each megapixel consists of 1,000,000 pixels.
Relative image resolution
The relative image resolution, also called dot, pixel or line density, indicates the detail accuracy based on the density of an image. It results from the number of pixels per unit length and is given as dpi (dots per inch), ppi (pixel per inch), lpi (lines per inch).