Dynamic range

Dynamic range, and dynamic range or just dynamic contrast range or designated, in general, technical, physical or mathematical contexts, the ratio of maximum and minimum of a physical variable or function. Typically, the auxiliary units B ( BEL) or NP ( neper ) can be used for display.

Nature and Technology

The dynamic range is the ratio of the maximum to the minimum signal strength of natural events such as pressure ( eg sound ) or radiation (eg light ), etc..

The recording, transmission or reproduction of such events, however, can often capture only a portion of the actual events, because the technology only captures a smaller dynamic range:

  • The lower limit of the detectable range is based in part on seismic noise, superimposed on the smallest useful signals.
  • The maximum signal size ( override ) the technical component used limits the dynamic range to the top.

Thus, there is often a smaller dynamic range in the art to natural differences.

Sound equipment

In the sound of the dynamic range of an audio system specifies the range in which the level of the audio signal can be usefully move, be it for recording, transmission or reproduction. This value is usually expressed in dB.

Down the dynamic range by the noise floor of the audio system is limited. If signals below this level be controlled, it would be masked by the noise and be inaudible. Back to top of the dynamic range is limited by reaching the maximum dynamic range of the system with no audible distortion.

Since audio systems can not handle the large dynamic range of all natural sources, found in the sound engineering practice, often dynamic compression instead, that is, a deliberate reduction of the dynamic range. It depends on the design-related content purpose of the clay material produced and the desired target medium.

Optics

Contrast range

The contrast range as the ratio Km from minimum to maximum contrast is specified:

  • As a ratio; 1: Km [Example: 1:1000 ]
  • As optical density d ( density ), the logarithm of the optical power; log ( Km) [Example: d = 3.0 ]
  • As f-stops, the logarithm to the base 2; log2 ( Km) stops [Example: 10 f-stops ]
  • As bits, as well as a base 2 logarithm; log2 (Km ) bits [Example: 10 bit ]

Remarks:

  • The values ​​in dB difference by a factor of 2, depending on whether the optical signal or the electrical signal is considered by a detector.
  • The information in bits is not allowed for non-linear encoding. The non-linear 8-bit coding for monitors may represent contrast ratios of more than 1:4000.

Dynamic ranges of images

Both in moving images in film and video as well as in the photograph of the scale which is the quotient of the largest and smallest distinguishable from noise or grain brightness value. The quotient is usually given in 2 - logarithm as stops.

Again, it should be noted that the dynamic range of the motif (also subject contrast ) the technical means for receiving (camera, sensor, film) often far exceeds the transmission as well as for playback (screen, screen, paper, etc. ).

High contrast images ( HDR ) images can either be picked up by special cameras or created from an exposure series of ordinary images with low dynamic range (see HDRI generation of bracketing ). The individual images are combined together so that the subject contrast fully accounted for and absolute brightness values ​​are stored. In order to map an HDR image on a medium with much lower dynamic range (eg paper), has dynamic range compression ( tone mapping ) can be applied.

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