What are the main technical factors that influence the quality of our photos, to be kept in mind when choosing a digital camera.
Features digital camera
Resolution
The resolution which is one of the most important factors, always highlighted among the technical characteristics of a digital camera, but alone is not enough to obtain high quality photos.
Sensor
There are two types of sensor, the Ccd and the CMOS. The sensor, as it is easy to deduce, is used to measure the amount of light that passes through the lens by providing the right values for correct exposure.
Processing
The most critical factor, however, is the system that transforms raw data into a photographic image.
Inside each camera there is an internal processing system more or less advanced depending on the price range of the device consisting of buffer memory, image processing algorithms and jpeg compression.
Number of pixels
The number of pixels is calculated simply by multiplying the number of pixels of the base of the image by the number of pixels of the height of the image. For example 1.92 Mpixel (equivalent to pixels) are the result of an image of 1600 × 1200 pixels.
The megapixel, literally an acronym for millions of pixels, is an approximate unit of measurement introduced by the manufacturers to simplify the general public's understanding of the total amount of pixels present in the sensor.
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Most compact digital cameras are in 4: 3 format (1600 × 1200, 800 × 600, ...) while DSLR cameras retain the classic 3: 2 ratio of analog cameras.
Digital photo compression formats
The formats used to store the photos taken are: raw and jpeg.
The raw format is an option only for cameras above a certain price range, it is also called raw format because, being devoid of any processing and compression by the device, it does not cause loss of quality.
In addition, during computer processing it is possible to intervene on a wider range of parameters through special programs and to save the modified file countless times without loss of quality.
The Jpeg is instead a compressed format that allows you to significantly reduce the size occupied by our photos with consequences saving memory space and money to buy additional additional memory cards.
JPEG is the most used format for storing photos.
The JPEG standard defines two basic compression methods, one based on the use of the DCT transform with "lossy" compression, that is, with loss of information, the other on the use of a predictive method with "lossless" compression, that is without loss of information.
The basic "lossy" JPEG algorithm is called "baseline", and optional extensions of the "lossy" method have been defined for hierarchical and progressive compression.
The best quality / size ratio is around 90%.
As the compression level increases, you will notice increasingly visually evident artifacts.
Among these, the most typical for the JPEG format (as for all formats based on DCT) is squaring or "blocking"; in addition to it there are phenomena of "ringing" (Gibbs phenomenon) and "blurring" or "blur".
Unlike the raw format, it must be said that the jpeg format loses quality every time it is changed again, especially if high compressions are used.
If you plan to process our photos on your PC later, you should use jpeg compression with a maximum quality ratio (100%) to reduce the degradation of the photographic image to minimal levels.
Types of memory card
The memory used consists of a memory card available in various formats, Compact flash, SD, etc., depending on the camera.
The memory card, also commonly called memory card, is placed in a special slot inside the camera.
ISO sensitivity
Equivalent sensitivity is an important fact; many models are 100-200 ISO that can be set automatically, while others reach 1600 ISO and beyond with automatic or manual setting, facilitating photographs in low light conditions.
Types of digital cameras
The dimensions of digital cameras vary according to the model and their weight also changes.
The compact cameras are the smallest, the prosumers, a term obtained by merging the professional-consumer terms, have medium dimensions, the reflex cameras are the largest and most cumbersome especially if equipped with alternative lenses and other accessories.
PC connection ports
All digital cameras are equipped with ports for quick connection to the computer, for downloading photos, processing them with graphics programs and viewing them.
They can be connected to television, to view photos on a larger screen, and in some cases connection to a special printer is allowed for direct printing of the photos taken without going through the computer.
One or more accompanying programs are often also provided to transfer the images to the computer and possibly process them.
