Dynamic range

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Dynamic range , and dynamic range or just dynamics or contrast range , indicated in general technical, physical or mathematical relationships the ratio of maximum and minimum of a physical quantity or function . The auxiliary units of measurement B ( Bel ) or Np ( Neper ) are usually used for the display .

nature and technology

The dynamic range is the quotient of the largest measured signal strength to the smallest signal strength of natural events that can be distinguished from noise, such as pressure (e.g. sound) or radiation (e.g. light) etc.

The recording, transmission or playback of such events, on the other hand, can often only cover a section of the actual events, because the technical means only cover a smaller dynamic range:

  • The lower limit of the measurable range is due, among other things, to the background noise that superimposes the smallest useful signals.
  • The maximum signal size that can be generated (limitation) of the technical component used limits the dynamic range upwards.

This often results in a smaller dynamic range in technology compared to natural differences.

Sound engineering

In sound engineering , the dynamic range of an audio system indicates the range in which the level of the audio signal can usefully move, be it for recording, broadcasting or playback. This value is usually given in dB.

The lower dynamic range is limited by the noise floor of the audio system. If signals are modulated below this level, they would be masked by the noise and thus become inaudible. The dynamic range is limited upwards by reaching the maximum control of the system without audible distortion .

Since audio systems cannot process the large dynamic range of all natural signal sources, dynamic range compression is often used in audio engineering practice, i.e. a deliberate reduction in the dynamic range. It is based on the design and content purpose of the produced clay material and the desired target medium.

optics

Contrast range

The range of contrast as the ratio K m of minimum to maximum contrast is specified:

  • as a ratio; 1: K m    [example: 1: 1000]
  • as optical density d (Density), the decadic logarithm of the light output; log ( K m )    [example: d = 3.0]
  • in decibels , 10 times the decadic logarithm of the light output; 10 · log ( K m )    [example: 30 dB]
  • in decibels, 10 times the decadic logarithm of the power at the detector; 10 · log ( P t )    [example: 60 dB]
  • as f-stops , the logarithm to base 2; log 2 ( K m ) f-stops    [example: 10 f-stops]
  • as light values (EV), the logarithm to base 2; log 2 ( K m ) levels    [example: span 10 EV]
  • as bits, also as a logarithm to base 2; log 2 ( K m ) bits    [example: 10 bit]

Remarks:

  • The values ​​in decibels differ by a factor of 2, depending on whether the optical signal or the electrical signal is viewed after a detector.
  • Specification in bits is not permitted with non-linear coding. The non-linear 8-bit coding in monitors can display contrast ratios of over 1: 4000.

Dynamic ranges of images

Representation of dynamic range from subject to image

For moving images in film and video as well as in photography, the dynamic range describes the quotient of the highest and lowest brightness value that can be distinguished from noise or grain. The quotient is usually given in the logarithm of two as f-stops.

Here, too, it can be stated that the dynamic range of the motif (also motif contrast ) often far exceeds that of the technical equipment for recording (camera, sensor, film) for transmission and for reproduction (canvas, screen, paper, etc.).

medium Dynamic range, specified in f-stops Dynamic range, ratio specification
Image sensor of a high-end digital cinema camera up to 17 (a) up to approx. 1: 130000
TIFF file 16 1: 65536
Image sensor of a high-end digital camera until approx. 15 up to approx. 1: 30000
Human eye approx. 13-14 (b) approx. 1: 8000-1: 16000
Black and white negative film until approx. 12 up to approx. 1: 4000
Color negative film until approx. 11-12 up to approx. 1: 2000-1: 4000
Compact camera approx. 10-11 approx. 1: 1000-1: 2000
LC display approx. 7.5-9 approx. 1: 200-1: 500
Jpeg file 8th 1: 256
Slide film approx. 6–8 approx. 1: 64-1: 250
Photo paper approx. 5 (c) approx. 1:32
(a)Around 2010 the dynamic range of the digital camera sensor ( digital cinema camera Arri Alexa, dynamic range approx. 13.5 f-stops) reached that of the analog film material.
(b) The indication '20' mentioned in other places takes into account the adaptation due to pupil changes.
(c) In terms of contrast, photo paper is the weakest link in the chain of the photographic process.

High-contrast images ( HDR images ) can either be recorded by special cameras or created from a series of exposures of ordinary images with a low dynamic range (see HDRI generation from series of exposures ). The individual recordings are combined with one another in such a way that the subject contrast is fully recorded and absolute brightness values ​​are saved. In order to be able to reproduce an HDR image on a medium with a significantly lower dynamic range (e.g. paper), dynamic compression ( tone mapping ) must be used.

Individual evidence

  1. ↑ The indication '17' refers to the manufacturer RED . Andrew Silvers: Camera Sensors: Four Components to Image Quality , Lulu.com. ISBN 978-0-359-08654-2 , 2018, p. 24.
  2. ↑ a b Gabriel Eilertsen: The high dynamic range imaging pipeline , Dissertation No. 1939, Linköping University, Division of Media and Information Technology, Department of Science and Technology, Nörrköping, 2018, Chapter 1.1.3.
  3. ^ A b Klaus Kindermann, Reinhard Wagner: Fascination Photography - Master School: The book for photos that inspire , Franzis, 2010, ISBN 978-3-645-60088-0 , p. 323
  4. ↑ Paul Carroll: Nikon D850 Sensor Review: First DSLR to hit 100 points , DXOMark, October 6, 2017, accessed January 3, 2020.
  5. ^ Jeanine Leech: Magic Light and the Dynamic Landscape: Take Advantage of Light and Weather , Amherst Media, Inc., 2014, ISBN 978-1-60895-729-3 , p. 118
  6. ↑ cameras vs. the human eye , Cambridgeincolour.com, accessed January 4, 2020.
  7. ↑ Jack James: Digital Intermediates for Film and Video , Focal Press, 2014, ISBN 978-0-240-80702-7 , p. 111.
  8. ↑ a b c Jürgen Gulbins, Rainer Gulbins: The shot: using time, aperture, ISO and focal length in a targeted manner when taking photos , dpunkt.Verlag, ISBN 978-3-89864-749-6 , p. 51
  9. ↑ Lars Svanberg (Ed.), The EDCF Guide to Digital Cinema Production , 2nd Edition, 2013, ISBN 978-0-240-80663-1 , p. 18.
  10. ↑ c't digital photography, Noble compacts against system cameras , issue 06/2018, p. 60.
  11. ^ Roger N. Clark: Digital Camera Reviews and Sensor Performance Summary , accessed January 3, 2020.
  12. ↑ Peter Badel: The Visualization of Emotions in Binary Code - Reflections on the Aesthetics of the Digital , in: Klaus Rebensburg (Ed.), Web, Film, Media, Computer - Reality and Visions of the Information Society , Conference Series, Berlin-Brandenburg Academy of Sciences, Vol. 2010, 7th – 9th July 2010, ISBN 978-3-7983-2310-0 , p. 43
  13. ↑ Andreas Martin: The best camera in the world: The human eye + comparison with photography (aperture, angle of view, focal length, focus and dynamic range) , May 23, 2017, accessed on January 3, 2020.
  14. ^ Rainer Zerback: Photographing Cars: Technology, Design, Practice , mitp, 2011, ISBN 978-3-8266-5564-7 , p. 72.

literature

  • Helmut Röder, Heinz Ruckriegel, Heinz Häberle: Electronics. Volume 3: Communication Electronics. 5th edition. Verlag Europa-Lehrmittel, Wuppertal 1980, ISBN 3-8085-3225-4 .
  • Thomas Görne: Sound engineering. Fachbuchverlag Leipzig in Carl Hanser Verlag, Munich et al. 2006, ISBN 3-446-40198-9 .
  • Hubert Henle: The recording studio manual. 5th edition, GC Carstensen Verlag, Munich, 2001, ISBN 3-910098-19-3
  • Gustav Büscher, Alfred Wiegelmann: Little ABC of electroacoustics (= Radio-Praktiker-Bücherei. Vol. 29 / 30a). 6th, completely revised and expanded edition. Franzis, Munich 1972, ISBN 3-7723-0296-3 .

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