# Color Theory/HDR

HDR

## DR

Dynamic range (DR):
* is the ratio between the largest and smallest values that a certain quantity can assume. It is often used in the context of signals, like sound and light. That technology also improves other aspects of transmitted images, such as color gamut
* The maximum contrast of an image is the contrast ratio or dynamic range
types of DR:
* LDR = low DR
* SDR (Standard Dynamic Range): 0.05 nits - 100 nits
* HDR (High Dynamic Range): 0.0005 nits - 10,000 nits. Also known as wide dynamic range, extended dynamic range, or expanded dynamic range, is a dynamic range higher than usual.
* Human DR: Human vision: can detect brightness levels as low as 0.000001 nits and as high as 100,000,000 nits
The candela per square metre is the unit of liminance in the International System of Units . The nit (symbol: nt) is a non-SI name also used for this unit
Defining HDR image and image sequence formats and attributes
* Peak luminance
* White points
* Contrast – spatial and temporal
* Dark levels
3 levels of monitor brightness:
* a low brightness if they have a peak brightness below 300 nits
* a standard brightness if they have a peak brightness between 300 and 350 nits (SDR)
* a high brightness if they have a peak brightness above 350 nits ( HDR )
Dynamic ranges of common devices :
| Device | Stops | Contrast ratio |
| Glossy photograph paper | 7 (7–7$^2$⁄$_3$) | 128:1 |
| LCD | 9.5 (9-11) | 700:1 (500:1Template:Snd2000:1) |
| Typical cellphone camera | ~10Template:Fv | varies |
| Negative film (Kodak VISION3) | 13 | 8000:1 |
| Human eye | 10–14 | 1000:1Template:Snd16,000:1 |
| OLED or quantum dot | 13.2-20.9 | 9500:1Template:Snd2,000,000:1 |
| High-end DSLR camera (Nikon D850) | 14.8 | 28,500:1 |
| Digital cinema camera (Red Weapon 8k) | > 16.5 | 92,000:1 |
| | Minimum peak luminance (Brightness in cd/m$^2$) | Range of color (Color gamut) | Minimum Color depth | Typical dimming technology | Maximum black level luminance (Brightness in cd/m$^2$) | Maximum backlight adjustment latency (Number of video frames) |
| DisplayHDR 400 | 400 | sRGB | 8 bit (24-bit) | Screen-level | 0.4 | 8 |
| DisplayHDR 500 | 500 | WCG* | 10-bit (30-bit) | Zone-level | 0.1 | 8 |
| DisplayHDR 600 | 600 | WCG* | 10-bit (30-bit) | Zone-level | 0.1 | 8 |
| DisplayHDR 1000 | 1000 | WCG* | 10-bit (30-bit) | Zone-level | 0.05 | 8 |
| DisplayHDR 1400 | 1400 | WCG* | 10-bit (30-bit) | Zone-level | 0.02 | 8 |
| DisplayHDR 400 True Black | 400 | WCG | 10-bit (30-bit) | Pixel-level | 0.0005 | 2 |
| DisplayHDR 500 True Black | 500 | WCG | 10-bit (30-bit) | Pixel-level | 0.0005 | 2 |
| DisplayHDR 600 True Black | 600 | WCG | 10-bit (30-bit) | Pixel-level | 0.0005 | 2 |
High dynamic range (HDR)
* HDR rendering
* HDR TV
HDR
* HDRI = High dynamic range imaging. The set of imaging technologies and techniques that allow to increase the dynamic range of images or videos. It covers the acquisition, creation, storage, distribution and display of images and videos
** HDRR = High-dynamic-range rendering
*** HDRP = HIGH DEFINITION RENDER PIPELINE
** HDR display
** HDR file formats

## formats

Formats that are only used for HDR storage purpose:
* AVIF
* Raw image formats
* Formats that use a linear transfer function with high bit-depth
* Formats that use a logarithmic transfer function
* OpenEXR
* ACES
HDR formats that can be used for both storage and transmission to displays, such as:
* HDR10
* HDR10+
* Dolby Vision
* HLG

## programs

* HDRI / Radiance image processing algorithms for Python
* piccante: The hottest High Dynamic Range (HDR) Library

## links

* High Dynamic Range Explained by Eric Chan 10-10-2023
* displayhdr.org
* Learn OpenGL: HDR
* hdr-faq by ARRI
* greg benz photography: hdr
* Towards an HDR-capable ICC PCS by Chris Lilley World Wide Web Consortium (W3C) June 2020

## References

* ↑ HDR workflows: ITU vs ICC by Luke Wallis
* ↑ Buser, Pierre; Imbert, Michel (1992). Vision. MIT Press. p. 53. ISBN 978-0-262-02336-8. nit luminance.
* ↑ Boyd, RLF, ed. (1992). Astronomical Photometry. Springer. p. 9. ISBN 978-0-7923-1653-4.
* ↑ Terry Relph-Knight (July 16, 2018). "High Dynamic Range: The quest for greater image realism". ZD Net. Retrieved 2022-12-25.
* ↑ "Of Phones, Pixels and Photons – why a 100 mp cell phone is not a GFX 100 - Luminous Landscape". 2021-04-27.
* ↑ Brian Wagner (July 2, 2020). "HDR Nits are a Lie: It's Time to Embrace the Stop". Retrieved 2022-12-25.Template:Sps
* ↑ "Red Weapon 8k Rating by DxOMark". 2017-01-10. Archived from the original on 2017-06-19.
* ↑ High-dynamic-range rendering in wikipedia