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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Clarifying High Dynamic Range (HDR)
PART OF SMPTE’S MONTHLY EDUCATION SERIES
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SMPTE Educational Webcast Sponsors
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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SMPTE Monthly Education Webcast Series
Series of monthly 1-hour online, interactive webcasts covering a variety of technical topics
Free professional development benefit for SMPTE members
Sessions are recorded for member viewing convenience.
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• Views and opinions expressed during this SMPTE Webcast are those of the presenter(s) and do not necessarily reflect those of SMPTE or SMPTE Members.
• This webcast is presented for informational purposes only. Any reference to specific products or services do not represent promotion, recommendation, or endorsement by SMPTE
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Today’s Guest Speaker
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Joseph SlomkaVice President and
Principal Color Scientist
FotoKem
Your Host
Joel E. WelchDirector of Education
SMPTE
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Introduction
This presentation will go over 3 main HDR topics
Effects of HDR display on the perception of resolution and depth
Experiences in support grading a HDR theatrical and a HDR video
How HDR can affect the artistic process
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What is HDR
HDR is a technology that allows more more dynamic range than current displays. It allows for uncrushed blacks and unclipped whites
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Introduction
This is going to cover captured motion pictures
Much of this will apply, but differently, to Computer Graphics and VFX
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Benefits of HDR
Acquisition• Captures a more complete version of the scene
• Display• Reproduces greater detail
• More natural image appearance*
• The ability to have greater local contrast
• The ability to have greater overall contrast
• Increased perception of color
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Goals
Connect the technical, scientific and artistic
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A little about light
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Stops
Stops are a way of describing an amount of light
One stop represent a doubling of light
• Increasing one stop doubles the amount of light
• Decreasing one stop halves the amount of light
They have been used in photography because relevance to the process and have been adopted by digital cinematography
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How Much DR is HDR?
Acquisition
Display
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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How Much DR is HDR?
Acquisition
• Film • Greater than 14 stops (Kodak 5219)
• A good starting point for acquisition
Display• DCI DCP
• Around 10 stops at rated contrast ratio(2000:1, 1200:1)
• More than that is where HDR begins
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Human Perception and Dynamic range TYING TOGETHER HDR, UHD, AND HFR
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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HDR , 4K,HFR: How They Fit Together
Higher dynamic range allows for more image contrast
The higher contrast allows for greater perception of detail
Higher luminance increases the perception of flicker
Higher frame-rate reduces flicker
Each of these technologies increases the value of the other creating better pixels
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Visual Limits
Dynamic range of vision
23-43 stops
Simultaneous dynamic range
10-14 stops
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Contrast, Resolution and HDR
Ability to see contrast dependent on brightness
Higher contrast between pixels allows for greater perception of detail
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HDR and Resolution
Contrast sensitivity function
Contrast is a key part of identifying detail
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Contrast and Resolution
Contrast and Resolution
Contrast as Resolution
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Contrast Sensitivity Function
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Attribution By: Star Whitt-FrousiakisLocated at: commons.wikimedia.org/wiki/File:Contrast_Sensitivity_vs._Spacial_Frequency.png
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Contrast Sensitivity Changes With Brightness
You become more sensitive to high frequency detail in brighter light
Another way to say it
• The brighter an image is the less contrast you need to see detail
• From 90-900-9000 cd/m^2 there is a significant change
• http://webvision.med.utah.edu/imageswv/KallSpat24.jpg
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Contrast and Depth Perception
Stereo images are only part of seeing depth
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Contrast and Depth
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Ways Depth is Perceived
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http://www.hitl.washington.edu/projects/knowledge_base/virtual-worlds/EVE/III.A.1.c.DepthCues.html
Accommodation
Convergence
Binocular Parallax
Monocular Movement Parallax
Retinal Size
Linear Perspective
Texture
Position
Aerial Perspective
Shades and Shadows
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Ways Depth is Perceived
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http://www.hitl.washington.edu/projects/knowledge_base/virtual-worlds/EVE/III.A.1.c.DepthCues.html
Accommodation
Convergence
Binocular Parallax
Monocular Movement Parallax
Retinal Size
Linear Perspective
Texture• The closer we are to an object the more detail we can see of its surface texture. • Objects with smooth textures are usually interpreted being farther away. This is especially true if the surface
texture spans all the distance from near to far.
Position
Aerial Perspective
Shades and Shadows• The location of a light source and see objects casting shadows on other objects• bright objects seem to be closer to the observer than dark ones.
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Flicker and Luminance
Flicker can be described with temporal sensitivity
As average luminance increases so does flicker sensitivity
Color is adaptive, flicker is not
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QuestionsASK AWAY
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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HDR and the artistic process
A Different Look
How can it help the story?
How can it hurt?
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Trickshot
Gale Tattersall - Director of Photography
Curtis Clark ASC– HDR and ACES technical consultant
Senior Colorist – John Daro
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Trickshot
Designed to show off the C300MKII
Ground up HDR
• Onset HDR mastering
ACES 1.0
• Pre-release
NAB delivery
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Onset with HDR
Trick Shot
Preproduction Canon monitor 400nit
• Available this month
Using Canon raw
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SDR Grade
An experienced DP and Colorist leaves little chance for unnecessary drama
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Secret HDR Grade
Secret 2000 nit 4k prototype display with SMPTE 2084 encoding
Graded on the show floor using ACES 1.0 on the Mistica
Separate grade on selected shots
• Tradeshow goodness
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Notes
HDR monitoring on set with 400 nit HDR display
HDR presentation and final grade on 2000 nit
Sense of depth
Texture
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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San Andreas
Director of Photography – Steve Yedlin
Senior Colorist - Walter Volpatto
Dolby Technical Lead - Thaddeus Beier
Dolby Assistant Colorist -Rick Taylor
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Feature Color Correction
San Andreas
Theatrical Master
Video Master 108 nits
Dolby Vision 4000 nits
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San Andreas
Acquired with ARRI Alexa
Using custom color science from Steve Yedlin.
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Strong Vision
The photography was captured with a specific vision
The DCP grade was made in a way similar to a traditional film grade
• Very few windows, highlights were allowed to blow out if that is how they fell on the rendering
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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HDR Color Setup
The look for the 2d version had a directed artistic vision
Preserving that look and mapping it to HDR was central to the design process
The HDR lookup table was set so that everything below diffuse white was left untouched.
Above diffuse white the lut was stretched to show additional highlight detail, then preserving the original roll off
No access to an HDR display before the session
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HDR Color Setup Results
The DCP material was graded in a way that did not constrain the dynamic range and was ideal for HDR
Many scenes were completely unchanged
Many scenes were mostly unchanged
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Unexpected Results and Notes
Technically the look of the film was largely preserved
• Most of a frame is composed below diffuse white
The notes from the grading colorist are nuanced
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Consistent Pixels : Inconsistent Feel
Ideally the state of adaptation would remain constant over the picture with the highlights being perceived as specular detail
• This didn’t hold up everywhere
Vistas, cityscapes, outdoors, fire and machines were amazing
Scene with sufficient highlight caused faces to feel dim
• Vision adjusted to specular light, not nominal
• This was true even with just 1 more stop of range
Even a small amount of highlight in a scene caused the issue
Technically correct, artistically incorrect
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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Inconsistent Look
Unwanted details
• Lights become directional
• New light shapes
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Colorist Notes
After the project was delivered 4 different paths were identified:
1. Start from scratch• No tone map or trims
2. Stretch the signal• Extend the contrast, blacker blacks, whiter whites
3. Raise exposure• Make everything brighter
4. Combination • Make it brighter with limited additional highlights
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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My Notes
It all makes sense once you see it
The way we see and the way we create are not the same
Cinematography is concerned about ratios
• We should be as well
Different results
• Trickshot vs San Andreas
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QuestionsASK AWAY
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Problems in HDR
Exposure and Dynamic Range
Exposure- Brightness or darkness of a scene
Dynamic range- the range of available light
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No Agreed Upon Image Parameters
There is no standard for black, white or grey in HDR
This is a problem
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This is One of the Two Big Headaches
A lot of high tech solutions are being developed to deal with this issue
No desire to limit all masters to the smallest dynamic range
No display reaches the highest value of 10,000
Capture becomes extremely challenging
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Wide Variety in Display Performance
Display peak white values vary greatly
• 400-4000cd/m^2
Black levels as well
• LCD to OLED blacks
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Current TV’s Have a Lot of Variability
Current home TV’s have a lot of variability
Target master luminance is typically 100 nits
Homes can have 250-400 nits
However dynamic range is fixed
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Won’t someone think of the Children Editors Advertisers?
If exposure values vary to much editorial becomes impossible
Selling ads also becomes difficult viewing an SDR ad in HDR content could look very different
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Picking a Point, nit Picking
Cinematographers already solved this issue
• Build the image around people
• Dynamic range built around that
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Good HDR comes from artists
Although the cameras capture HDR it needs artistic direction
Post ‘conversion’ of HDR is more difficult than starting with HDR
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QuestionsASK AWAY
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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The Wild West of HDR
Several Specifications, But No Standards
Competing specifications mean no standards
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Competing Formats
BBC
Technicolor
Dolby
Phillips
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No Perfect Answer
Each solution comes from a specific viewpoint and solves specific issues
The rooms I am in mention Dolby and BBC as the main proposals
• I may just be in the wrong rooms
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SMPTE Monthly Education Webcast Series: Clarifying High Dynamic Range (HDR)
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BBC
Attempts to be compatible with existing monitors, TV and distribution
Keeps the midtone and shadows the same as rec709
Adjusts highlights for the extra dynamic range
No-metadata
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Dolby
A new approach not backwards compatible
Based on decades of vision research
Fully designed end to end
Provide SDR compatibility mode
PQ encoding
Uses metadata to provide display mapping
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Technicolor
Encoding curve with parameters
Uses metadata
Supports a variety of encoding scenarios
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Philips
Parameter based HDR
Uses HDR grade as starting point
Tone-mapping and metadata produce the Standard Dynamic range
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Blu-ray Also Complicates This
As part of the Blu-ray HDR specification there is a limit to an APL of 400 nits
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Q&A – Verbal Questions Take Priority!
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Joel E. Welch
Joseph SlomkaVice President and
Principal Color Scientist
FotoKem
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