High dynamic range

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For the technology related to HDR displays, see High Dynamic Range (color representation). For the photography technique, see High Dynamic Range (photography technique).

High dynamic range (HDR) is a dynamic range higher than usual. The term is often used in discussing display devices, photography, 3D rendering, and sound recording including digital imaging and digital audio production. The term may apply to an analog or digitized signal, or to the means of recording, processing, and reproducing such signals.[1]

Imaging[edit]

High dynamic range imaging (HDRI) refers to the acquisition, creation, storage, distribution or display of images and videos that have a higher dynamic range than traditionnal images and videos.[2] This can be done with the HDR photography technique, with the use of cameras that natively have a high dynamic range or with computers (for example with the use of HDR rendering). The resulting image can be saved in an traditionnal image and video format or in an high dynamic range format. It can also be used for traditionnal SDR displays or for HDR displays.

Capture and creation[edit]

Photography technique[edit]

Main article: High Dynamic Range (photography technique)

In photography and videography, High Dynamic Range (HDR) is a technique used to increase the dynamic range of captured photos and videos. It consist of capturing multiple frames of the same scene but with different exposures and then combining them into one resulting into a dynamic range higher than those of individualy captured frames.

It includes the compositing and tone mapping of images to extend the dynamic range beyond the native capability of the capturing device.[3][4]

Sensors[edit]

Modern CMOS image sensors can often capture a high dynamic range from a single exposure. The wide dynamic range of the captured image is non-linearly compressed into a smaller dynamic range electronic representation.[5] However, with proper processing, the information from a single exposure can be used to create an HDR image.

Such HDR imaging is used in extreme dynamic range applications like welding or automotive work. In security cameras the term used instead of HDR is "wide dynamic range". Because of the nonlinearity of some sensors image artifacts can be common. Some other cameras designed for use in security applications can automatically provide two or more images for each frame, with changing exposure[citation needed]. For example, a sensor for 30fps video will give out 60fps with the odd frames at a short exposure time and the even frames at a longer exposure time. Some of the sensors on modern phones and cameras may even combine the two images on-chip so that a wider dynamic range without in-pixel compression is directly available to the user for display or processing[citation needed].

Rendering[edit]

Main article: High-dynamic-range rendering

High Dynamic Range Rendering (HDRR or HDR rendering) is a way of rendering computer generated images with a high dynamic range.

High-dynamic-range rendering (HDRR) is the real-time rendering and display of virtual environments using a dynamic range of 65,535:1 or higher (used in computer, gaming, and entertainment technology).[6]

Storage[edit]

The term high dynamic range format designates image and video file formats that are able to store more dynamic range than traditionnal 8-bit gamma formats.

This includes:

Distribution and display[edit]

Main article: High Dynamic Range (color representation)

High Dynamic Range displays (HDR displays) are displays compatible with a list one HDR formats such as HDR10, HDR10+, Dolby Vision and HLG.

HDR video refers to a video signal with greater bit depth, luminance and color volume than standard dynamic range (SDR) video which uses a conventional gamma curve.[7]

On January 4, 2016, the Ultra HD Alliance announced their certification requirements for a HDR display.[8][9] The HDR display must have either a peak brightness of over 1000 cd/m2 and a black level less than 0.05 cd/m2 (a contrast ratio of at least 20,000:1) or a peak brightness of over 540 cd/m2 and a black level less than 0.0005 cd/m2 (a contrast ratio of at least 1,080,000:1).[8][9] The two options allow for different types of HDR displays such as LCD and OLED.[9]

Some options to use HDR transfer functions that better match the human visual system other than a conventional gamma curve include the Hybrid Log-Gamma (HLG) and Perceptual Quantizer (PQ).[7][10][11] HLG and PQ require a bit depth of 10-bits per sample.[7][10]

Audio[edit]

XDR (audio) is used to provide higher-quality audio when using microphone sound systems or recording onto cassette tapes.

HDR Audio is a dynamic mixing technique used in EA Digital Illusions CE Frostbite Engine to allow relatively louder sounds to drown out softer sounds.[12]

Dynamic range compression is a set of techniques used in audio recording and communication to put high-dynamic-range material through channels or media of lower dynamic range. Optionally, dynamic range expansion is used to restore the original high dynamic range on playback.

Radio[edit]

In radio, high dynamic range is important especially when there are potentially interfering signals. Measures such as spurious-free dynamic range are used to quantify the dynamic range of various system components such as frequency synthesizers. HDR concepts are important in both conventional and software-defined radio design.

Instrumentation[edit]

In many fields, instruments need to have a very high dynamic range. For example, in seismology, HDR accelerometers are needed, as in the ICEARRAY instruments.

Realtime HDR vision[edit]

Mann's HDR (high-dynamic-range) welding helmet augments the image in dark areas and diminishes it in bright areas, thus implementing Computer-mediated reality.

In the 1970s and 1980s, Steve Mann invented the Generation-1 and Generation-2 "Digital Eye Glass", as a vision aid to help people see better, with some versions being built into welding helmets for HDR vision [13] [14] [15] [16] See also, IEEE Technology and Society Magazine 31(3)[17] and the supplemental material entitled "GlassEyes". [18]

See also[edit]

References[edit]

  1. ^ Robertson, Mark A.; Borman, Sean; Stevenson, Robert L. (April 2003). "Estimation-theoretic approach to dynamic range enhancement using multiple exposures". Journal of Electronic Imaging. 12 (2): 220, right column, line 26219–228. doi:10.1117/1.1557695. The first report of digitally combining multiple pictures of the same scene to improve dynamic range appears to be Mann
  2. ^ Frédéric Dufaux, Patrick Le Callet, Rafal Mantiuk, Marta Mrak (2016). High Dynamic Range Video - From Acquisition to Display and Applications. doi:10.1016/C2014-0-03232-7. ISBN 978-0-08-100412-8.CS1 maint: multiple names: authors list (link)
  3. ^ "Compositing Multiple Pictures of the Same Scene", by Steve Mann, in IS&T's 46th Annual Conference, Cambridge, Massachusetts, May 9–14, 1993
  4. ^ Reinhard, Erik; Ward, Greg; Pattanaik, Sumanta; Debevec, Paul (2005). High dynamic range imaging: acquisition, display, and image-based lighting. Amsterdam: Elsevier/Morgan Kaufmann. p. 7. ISBN 978-0-12-585263-0. Images that store a depiction of the scene in a range of intensities commensurate with the scene are what we call HDR, or "radiance maps". On the other hand, we call images suitable for display with current display technology LDR.
  5. ^ Arnaud Darmont (2012). High Dynamic Range Imaging: Sensors and Architectures (First ed.). SPIE press. ISBN 978-0-81948-830-5.
  6. ^ Simon Green and Cem Cebenoyan (2004). "High Dynamic Range Rendering (on the GeForce 6800)" (PDF). GeForce 6 Series. nVidia. p. 3.
  7. ^ a b c T. Borer; A. Cotton. "A "Display Independent" High Dynamic Range Television System" (PDF). BBC. Retrieved 2015-11-01.
  8. ^ a b "UHD Alliance Defines Premium Home Entertainment Experience". Business Wire. 2016-01-04. Retrieved 2016-07-24.
  9. ^ a b c "What is UHD Alliance Premium Certified?". CNET. 2016-03-11. Retrieved 2016-07-24.
  10. ^ a b Adam Wilt (2014-02-20). "HPA Tech Retreat 2014 – Day 4". DV Info Net. Retrieved 2014-11-05.
  11. ^ Bryant Frazer (2015-06-09). "Colorist Stephen Nakamura on Grading Tomorrowland in HDR". studiodaily. Retrieved 2015-09-21.
  12. ^ EA DICE/Electronic Arts (2007). "Battlefield: Bad Company - Frostbite Engine Trailer" (video). Electronic Arts.
  13. ^ Quantigraphic camera promises HDR eyesight from Father of AR, by Chris Davies, SlashGear, Sep 12th 2012
  14. ^ Ackerman, Elise (31 Dec 2012). "Why Smart Glasses Might Not Make You Smarter". IEEE Spectrum. Retrieved 1 Jan 2017.
  15. ^ Mann, Steve (February 1997). "Wearable Computing: A First Step Toward Personal Imaging". IEEE Computer. 30 (2): 25–32. doi:10.1109/2.566147.
  16. ^ "A magical welding helmet that lets you see the world in HDR–in real-time". Archived from the original on 2016-03-28. Retrieved 2018-03-24.
  17. ^ Mann, Steve (Fall 2012). "Through the Glass, Lightly". IEEE Technology and Society Magazine. 31 (3): 10–14. doi:10.1109/MTS.2012.2216592.
  18. ^ "'GlassEyes': The Theory of EyeTap Digital Eye Glass, supplemental material for 'Through the Glass, Lightly'" (PDF). IEEE Technology and Society Magazine. 31 (3). Fall 2012.

External links[edit]

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