#Cinematography/Colour/Correction #Cinematography/Colour/Grading #Cinematography/Colour/Science #Senses/VisualPerception *** ## HUMAN PERCEPTION and GAMMA ENCODING Human visual perception has biologically evolved to discern more precisely between gradations in dark tones than to gradations in bright tones. This disproportional sensitivity to bright and dark tones enables us to perceive a wider range of luminance (from the brightest of day-lit skies, to the constellations in a moonless night sky-- And all through the same eyes!). Whereas humans perceive brightness and contrast in this non-linear fashion, digital camera sensors record and encode light differently. The values of light recorded by a digital sensor are first encoded in a linear fashion, wherein a quantity of twice the number of photons exposed to the camera sensor equate to a value of twice the brightness in the digital signal. A digital image is artificially recorded by means of a linear equation, and must be Gamma Encoded to appear 'naturalistic' to a human viewer. ### GAMMA CORRECTION Gamma Correction is a process whereby the relative brightness values or tones of a scene in a recorded image are subsequently rendered in a manner which, when *displayed* artificially, more closely reproduce what our eyes would perceive of the same scene in nature.^[[Understanding Gamma Correction - Cambridge in Colour](https://www.cambridgeincolour.com/tutorials/gamma-correction.htm)] ### HUMAN ADAPTATION A person's perception of an image is significantly influenced by ambient light levels and colour spectrums. This may be demonstrated when observing the optical illusion produced by The Contrast Effect.^[[WIKI - The Contrast Effect (Illusion)](https://en.wikipedia.org/wiki/Contrast_effect)] For this reason among many, several Gamma Targets have been established for common viewing environments equipped with Home Video Televisions, Theatrical Cinema Projections, and Computer Displays. Three of these Gamma Targets are summarized below, along with various intended viewing environments and corresponding display colour gamuts. ## STANDARD GAMMA TARGETS ### Gamma 2.2 - **TARGET AMBIENT ENVIRONMENT** - Fully-illuminated - Intended for desktop and laptop computer systems; Offices with bright overhead lighting; Rooms with exterior windows. The standard for Web streaming. - **COLOUR GAMUT** - sRGB (A derivative of Rec.709's primary chromaticities, but with a modified Transfer Function^[[WIKI - Rec.709's relationship to sRGB](https://en.wikipedia.org/wiki/Rec._709#Relationship_to_sRGB)]) ### Gamma 2.4 > [!Idea]- 'STANDARD' GAMMA TARGET > An excellent target for mezzanine-master delivery, and a standard among DVD-Video and Blu-Ray releases. Currently the most widely accepted standard. - **TARGET AMBIENT ENVIRONMENT** - Dark to moderate ambient light - Intended for home-video systems; Living rooms; Bedrooms; Lamp-illuminated desks. - **COLOUR GAMUTS** - Rec.601 (480i-SDTV) - Rec.709 (2K-HDTV - SDR) - Rec.2020 (4K-UHDTV - SDR & [WCG](https://en.wikipedia.org/wiki/Gamut#Wide_color_gamut)) - Rec.2100 (4K-UHDTV - HDR) ### Gamma 2.6 Intended for theatrical cinema projection. - **TARGET AMBIENT ENVIRONMENT** - Fully-darkened environment - **COLOUR GAMUT** - DCI-P3 (2K-DCI and 4K-DCI) ## CONVERSION / TRANSFORMS It is possible to 'convert' a program between various Gamma Target and Colour Gamut configurations by conducting Transform Operations and / or Colour-Correction Trim Passes. <br> ## ALSO ### VISUAL SCIENCE - [WIKI - Visual Perception](https://en.wikipedia.org/wiki/Visual_perception) - [WIKI - Photopic Vision](https://en.wikipedia.org/wiki/Photopic_vision) - [WIKI - Scotopic Vision](https://en.wikipedia.org/wiki/Scotopic_vision) - [WIKI - Gamma Correction](https://en.wikipedia.org/wiki/Gamma_correction) <br> - [WIKI - Planckian locus](https://en.wikipedia.org/wiki/Planckian_locus) - [WIKI - Colour Vision](https://en.wikipedia.org/wiki/Color_vision) - [WIKI - Colour Space](https://en.wikipedia.org/wiki/Color_space) ### DYNAMIC RANGE - [WIKI - SDR - Standard Dynamic Range](https://en.wikipedia.org/wiki/Standard-dynamic-range_video) - [WIKI - HDR - High Dynamic Range](https://en.wikipedia.org/wiki/High-dynamic-range_television) ### COLOUR GAMUTS - [WIKI - Colour Gamut](https://en.wikipedia.org/wiki/Gamut#) - [WIKI - Rec.601](https://en.wikipedia.org/wiki/Rec._601) - [WIKI - Rec.709](https://en.wikipedia.org/wiki/Rec._709) - [WIKI - sRGB](https://en.wikipedia.org/wiki/SRGB) #### WIDE COLOUR GAMUTS - [WIKI - DCI-P3](https://en.wikipedia.org/wiki/DCI-P3) - [WIKI - Rec.2020](https://en.wikipedia.org/wiki/Rec._2020) - [WIKI - Rec.2100](https://en.wikipedia.org/wiki/Rec._2100) ### RESOLUTION - [WIKI - 480i-SDTV](https://en.wikipedia.org/wiki/Standard-definition_television) - [WIKI - 2K-FHDTV](https://en.wikipedia.org/wiki/High-definition_television) - [WIKI - 4K-UHDTV](https://en.wikipedia.org/wiki/Ultra-high-definition_television#Resolution) - [WIKI - 8K-UHDTV](https://en.wikipedia.org/wiki/8K_resolution#7680_×_4320) - [WIKI - DCI](https://en.wikipedia.org/wiki/Digital_Cinema_Initiatives#2D_image) - 2K-DCI - 4K-DCI