Wide Color Gamut SET EXPO 2016 31 AUGUST 2016 Eliésio Silva Júnior Reseller Account Manager E/ [email protected] T/ +55 11 3530-8940 M/ +55 21 9 7242-4211 tek.com Anatomy Human Vision CIE Chart Color Gamuts Wide Color Gamut Gamma and High Dynamic Range 2 Basic Anatomy - Human vision system PHYSICAL PART/ELEMENTS • Eye, Lens and Retina ▪ Rods ▫ Sensitive to Blue-green light ▫ Used for vision under dark-dim conditions. ▪ Cones ▫ 3 Types of Cones Sensitive to either long wavelengths of light (red light) medium wavelengths of light (green light) short wavelengths of light (blue light) ◦ Optic nerve http://webvision.med.utah.edu/index.html 3 Color Model – CIE color spaces NTSC (1953) BT709/sRGB BT2020 ~SMPTE C D65 white BT2020 NTSC (1953) Black BT709/sRGB (70% NTSC) White ~SMPTE C D65 white CIE-1931 chart CIE-1976 chart (More perceptually uniform than CIE-1931) • CIE 1931 XYZ color space ◦ Still foundation of most color models • Trichromatic stimulus (color value) • Lightness decreases towards not shown third dimmension • Saturation increases towards edges 4 ITU 601-7 & 709-5 Chromaticity ITU-R BT 601-7 601-7 525 CIE x CIE y Red 0.630 0.340 Green 0.310 0.595 Blue 0.155 0.070 White 0.3127 0.3290 ITU-R BT 709-5 709-5/601 625 CIE x CIE y Red 0.640 0.330 Green 0.300 0.600 Blue 0.150 0.060 White 0.3127 0.3290 31 AUGUST 2016 5 Wider Color - Chromaticity ITU-R BT 2020 CIE x CIE y Red 0.708 0.292 Green 0.170 0.797 Blue 0.131 0.046 White 0.31272 0.32903 ITU-R BT 709-5 709-5 CIE x CIE y Red 0.640 0.330 Green 0.300 0.600 Blue 0.150 0.060 White 0.3127 0.3290 31 AUGUST 2016 6 Wider Color - Chromaticity SMPTE 2048-1 Free Scale (FS) Gamut CIE x CIE y Red 0.73470 0.26530 Green 0.14000 0.86000 Blue 0.10000 -0.02985 White 0.31272 0.32903 X’Y’Z’ Color Space EG431-2 (P3) CIE x CIE y Red 0.680 0.3230 Green 0.2650 0.6900 Blue 0.150 0.06000 DCI P3 D65 0.3127 0.3290 31 AUGUST 2016 7 ACES Color Space - Academy Color Encoding System CIE x CIE y Red 0.73470 0.26530 Green 0.00000 1.00000 Blue 0.00010 -0.07700 Color image encoding system created by the Academy of Motion Picture Arts and Sciences that allows for a fully encompassing color accurate workflow. 31 AUGUST 2016 8 Wide(er) Color Gamut Percentage BT2020 NTSC (1953) BT709/sRGB (70% NTSC) ~SMPTE C D65 white . NTSC occupies 47.3% of CIE Chart 1931 . 709 occupies 33.5% of CIE chart 1931 CIE-1931 chart . DCI-P3 occupies 44.5% of CIE Chart 1931 . 2020 occupies 63.3% of CIE Chart 1931 9 Wide(er) Color Gamut 10 Wide(er) Color Gamut Video Ecosystem Transport QAM Stream Optical Baseband • File- DVB SET TOP MPEG DISPLAY Video Signal Based ISDB-TB BOX Video FTP 11 RGB and YPbPr Color Space • YPbPr color cube shows Parallel-Piped of RGB colors • Certain YPbPr values when converted to RGB will fall outside the allowed range and will be out of Gamut 12 525 RGB to SD (601) & HD (709) YPbPr 100% Color Bars SD 525 RGB SD 525 YPbPr HD 1080 YPbPr 13 HD/UHD (709) YPbPr and UHD (2020) HD 1080 YPbPr UHD (709) YPbPr UHD (2020) YPbPr / 525 UHD (709) & (2020) YPbPr 14 4K Monitoring – ITU-R BT.2020 15 Gamut 1616 Gamut 1717 Gamut 1818 Gamut 1919 Gamut 20 Gamut 21 Gamut 2222 Color Space 2323 Why does HDR look better than SDR ? • Are HDR screens brighter on average? • Are HDR screens darker on average with blacker blacks? • Is the average picture level (APL) unchanged? 31 AUGUST 2016 24 Why does HDR look better than SDR HDR RETAINS BRIGHT SPECULAR HIGHLIGHTS AS WELL AS DETAIL IN BLACKS WHICH CAN MAKE COLORS APPEAR MORE SATURATED. Sky Light: >500K nits Looking at the sun > 1 billion nits (don’t look at it) Shadows: .1 to 10 nits Lap top or TV: 100 to 200 nits With day adapted eye shadows (hard to see in bright daylight can be 10 nits. In living room, less than 0.1 nits 25 Total Visual Dynamic Range HDR MAPPING INTO CAMERA F-STOPS (0 STOP = 18% REFLECTANCE) 10^8 (5000 nits)8 6 Sunlight 10^6 Pull Sun light Bright adaption outdoor 24 4 outdoor Photopic - 10^4 with stops adaption some ST.2084 HDR HDR Display ST.2084 (100nits)2.5 Sony, ARRI, Canon ARRI, Sony, Bright adaption Bright (90%) 2 Adapted Eye Adapted Adapted Eye Adapted Indoor 7 10^2 - ~16 stops indoor ~7 lighting - stops Lighting - (18%) 20 stops (20nits) 0 (18%) 10^0 Mesopic -2 Moonlight moonlight Dark Adaption 10^-2 -4 Scotopic adaption starlight Push Dark 10^-4 Starlight -6 10^-6 (.08 nits) -8 Nits (cd/m^2) Stops 26 Potential Issues with Bright HDR displays • Color shift in the Mesopic-level adaption (dark viewing environment) • As light moves below Photopic (dominated by cones) and gets closer to Scotopic (dominated by rods) color saturation will diminish. • This may occur in dark scenes in low-light home theater. • Light/Dark Adaption (bleaching process rather than pupil size) • Sustained bright images cause the photo-pigment in the retina to reduce and can result in the perception of after images. • Dark adaption can take seconds or even minutes. Changes to dark scenes from bright scenes may take more time in dark theater as opposed to same scene in higher ambient light. • Viewing distance • Static adaption is only about 7 to 9 stops. • To take full advantage of HDR (> 9 stops) via local adaption, you have to be closer than 2 screen widths • If you do sit this close, you may get eye strain • Large Area Flicker • Strobing of high peak light levels may cause distress to some viewers. Perceptual flicker frequency may be increased since it is a function of retinal adaption. May contribute to PSE (BT.1702). • Frame rate judder may be more visible. 27 Proposed HDR Formats • SMPTE ST.2084:2014 High Dynamic Range Electro-Optical Transfer Function of Mastering Reference Displays “Dolby Vision” Perceptual Quantizer (PQ) based on Barten contour perception EOTF is inverse of OETF allowing .001 to 10K nits with 10-bits Current “Pulsar” display peaks at about 4K nits • Hybrid Log-Gamma, “HLG”, from BBC/NHK (ARIB STD-B67) Extends log processing (de-facto in many cameras) of high brightness peaks to mitigate blown-out or clipped whites Seamless “gamma” power-law processing in blacks as in BT.709/BT.2020 but without linear segment Displays can evolve to allow 400X to 800X increase in display Allows display EOTF to adjust system gamma to correct for surround illumination (i.e. 10 nits to 500 nits) 31 AUGUST 2016 28 Proposed HDR Formats • Philips Parameter-based from HDR master Embed low bit-rate HDR and SDR conversion parameters into metadata Extract parameters during decode and tune display for peak luma Optional Y’u’v’ encoding (more perceptually uniform) • Technicolor Video Mastering and Distribution Workflow Grade both an HDR and SDR master Vital to maintain “Artistic Intent” • Academy Color Encoding System (ACES) (dynamic range and wide color gamut preserving workflow, not an HDR format) 33 bit floating point 10-bit proxy output in stops (log2). 31 AUGUST 2016 29 Capturing a Camera RAW image 0% Black 18% Grey 90% Reflectance Gamma 10-bit Code-Value % (20 nits illumination) % % 10-bit Code-Value 10-bit Code-Value S Log 1 90 3 394 37.7 636 65 S Log 2 90 3 347 32.3 582 59 S Log 3 95 3.5 420 40.6 598 61 LogC 134 3.5 400 38.4 569 58 C-Log 128 7.3 351 32.8 614 63 ACES (proxy) ND ND 426 41.3 524 55 BT.709 64 0 423 41.0 940 100 31 AUGUST 2016 30 Camera (scene) referenced 709 to PQ LUT conversion Camera-Side Conversion Camera-sideBT.709 to conversion PQ BT.709 to PQ 100 2084 HDR 0% 2% 18 % 90% 100% 90 9 41 709 0 9 41 95 100 80 100nits SDR BT.709,100,1000 70 SDR BT.709,100,2000 SDR_2_HDR_CSBT709,100,1000 HDR 1000nits 0 37 58 75 76 i 60 SDR BT.709,100,5000 SDR_2_HDR_CSBT709,100,2000 i 50 HDR 2000nits 0 31 51 68 68 SDR_2_HDR_CSBT709,100,5000 i 40 HDR 5000nits 0 24 42 58 59 30 20 10 0 0 20 40 60 80 100 BT709 BT.709 %i IRE SDR and HDR displays DO NOT match. % or IRE Blacks are stretched in the BT1886 Display but not the PQ Display (matches scene) 31 AUGUST 2016 31 Studio Monitor referenced 709 to PQ LUT conversion Display-Side Conversion Display-side convBT.709 ersio n BT.7 09 to PQto PQ 1 0 0 2084 HDR 0% 2% 18 % 90% 100% 90 9 41 709 0 9 41 90 100 80 100nits HDR BT.709,100,1000 70 HDR BT.709,100,2000 SDR_ 2_HDR_DS BT 7 0 9 , 1 0 0 , 1 0 0 0 HDR 1000nits 0 22 52 74 75 i 60 HDR BT.709,100,5000 SDR_ 2_HDR_DS BT 7 0 9 , 1 0 0 , 2 0 0 0 i 50 HDR 2000nits 0 17 46 66 68 SDR_ 2_HDR_DS BT 7 0 9 , 1 0 0 , 5 0 0 0 i 40 HDR 5000nits 0 13 37 57 58 30 20 10 0 0 20 40 60 80 1 0 0 BT 7 0 9 BT.709 %i IRE SDR and HDR displays match % o r IRE Blacks are stretched in both the BT1886 and PQ Display 31 AUGUST 2016 32 SMPTE 2084 PQ Look Up Tables Linear Ramp Test Signal Look Up Table Look Up Table BT.709 SMPTE 2084 1000nits SMPTE 2084 1000nits Reference White 100nits Reference White 300nits 31 AUGUST 2016 33 Slog 2 Camera RAW to HDR HDR 1000 Nits Look Up Table Converted SLog2 to ST 2084 PQ 90% Reflectance White 75%, 18% Grey 58% Need HDR Monitor to view this image.