Digital photography has democratized since 2004 with the launch of the first digital entry level DSLR accessible for amateur (Nikon D70 and Canon 300D). From 2010, digital imaging has fully imposed by very superior performance analog photography (especially in high ISO). The film is replaced by a sensor. Digital photography offers two major advantages such as lack of film processing in complete darkness and instant viewing images on the LCD camera screen.

The diagram (right) shows the digital photograph in a whole. Outside of the mechanical system, identical to the analog photographic, digital imaging Globally these include a sensor and a processor.

Hardware - Features a sensor

Hardware - A sensor format

Software - Processor

The sensor is the digital camera soul. Without sensor, producing an image is impossible ; it is the basic component. As the film showed the base component of the analog photograph. It is a photosensitive electronic component for converting light radiation (UV, visible or IR) into an electrical signal. This alone represents a technological revolution in photography because it is significantly more effective than the film where the first historical use in astrophotography since the 80s, first by professionals and then later by wealthy amateurs.

It is characterized by :

  • His nature (CCD, CMOS BSI CMOS)
  • Its highly variable ratio depending on its applications
  • Its number/size of its photosites/photodiodes
  • Its matrix (BAYER, X-TRANS or Foveon)
  • Presence/absence of low-pass filter

The sensor format is important in its quantum efficiency (ratio between the useful signal and noise reading).

In digital photography, the APS-C and full frame (24x36) are the most common. The sensor size growth directly impacts a wider dynamic (the sensor saturates much more difficult in the highlights). The depth of field is also enlarged.

Each brand has developed its own processor (DIGIC Canon, Nikon EXPEED, for example). A camera has become a small computer. It is simply a microprocessor signal processing and control but what power ! A camera is nothing without a dedicated processor used in digital sensor and possible mechanical elements correlated because when we know its importance, one soon realizes that he can be much more powerful than the optical (without an extremely powerful and fast image processor, many zooms indecent amplitudes as a 18-200mm could not claim anything more than what they really are : real bottle ass !). This processor allows particularly globally in all devices (such as compact SLR) feats unimaginable in traditional film photography :

  • Bayer transformation
  • Noise reduction
  • Optimization of the write speed and work (for example image gusts)
  • Optical corrections in real time (such as distortion or chromatic aberration)
  • etc...

Digital photography concepts

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OBSERVATION AND IMAGERY

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Arnaud FIOCRET
 

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