The Visual Science of HDR Video

The Science of HDR Video By Sean T. McCarthy, ARRIS

As momentum builds in the market transition to 4K UltraHD, the emergence of high dynamic range (HDR) technology is drawing video engineers' attention to new issues that must be resolved if the full potential of a next-generation viewing experience is to be realized.

As various organizations pursue HDR standardization initiatives, the priority must be on choosing solutions from a broad perspective on visual response processes. Along with responsiveness to degrees of contrast, developers must consider several critical human perceptual factors. This will impact everything that's done in the creation and dissemination of video content from initial capture through production, post-production, and processing for distribution.

Light and dark adaptation

One key consideration is the human visual system's ability to adapt to varying light intensity, with key factors including changes in pupil diameter, the impact of luminance on retinal illuminance, the impact on light absorption from the bleaching of photoreceptor photo pigments, speed of adaptation and contrast sensitivity. Settings for HDR must take into account how the human eye adapts to a wide range of content in both bright and dark home environments, and intensely bright outdoor situations as well.

Bleaching adaptation: With the current generation of displays, we are just entering into a point where what is known as "bleaching adaptation" could become significant and impact a viewer's experience. This is the phenomenon that occurs when the eye adjusts to sustained periods of illumination. The bleaching impact will be an important consideration in determining what average and peak levels of HDR brightness should be in the context of temporal shifts in luminance, as the speed at which the eye can receive and interpret light and color will vary when bleaching adaptation is present.

Speed of response and adaptation: According to recent studies, the time course of dark adaptation, the speed at which the human eye adapts to decreased illumination, depends on the intensity and duration of preceding stimuli. If the preceding exposure was low enough that no significant photopigment bleaching occurred, then dark adaptation may also be measured on the time scale of seconds but slightly slower than light adaptation. For bleaching adaptation, dark adaptation may take longer, on the order of tens of seconds to minutes.

Effects of luminance and screen size on flicker perception

For HDTV content viewed on traditional screen sizes, flicker perception - the sensitivity to temporal changes across video frame sequences - has not been an issue. The same is true of judder, the perception of uneven or jerky video playback that arises from movement of objects, edges, or detail from one frame to the next.

Yet with the onset of HDR on large-screen displays, flicker sensitivity and judder could both affect the rate at which content is captured as well as the display frame and refresh rates. This particularly holds true for content captured at the 24 frame-per-second (FPS) rate used with films and episodic series, and could be even more problematic if the motion picture industry raises the capture frame rates to, say, 48 fps.

The effect of luminance on color perception

As luminance increases, so does the ability of the human visual system to discriminate between colors at ever smaller gradations. Consequently, more bits would be needed to code color without introducing noticeable errors, particularly at high luminance. Thus, 10-bit encoding may be expected as a minimum bit depth for HDR for any color space.

Effects of adaptation speed on program changes and commercials

The speed of light and dark adaptation has important implications for the impact of rapid local or global luminance changes in TV programming when HDR and non-HDR content is presented sequentially to viewers. This makes it important for HDR-formatted commercials to utilize the same parameter set for HDR programming. Conversely, non-HDR compliant commercials should not be placed with HDR programming.

The effect of the light field and context on brightness and color

Perceptions of brightness and color are not just a matter of luminance intensity. Variations in the light field across the frame can profoundly influence visual responses as well. Such nuances will come into play as content producers move to using HDR in the creation process. They will need to avoid relying on luminance specifications alone in ensuring their creative intent is conveyed to viewers.


HDR is bringing a welcome transformation in the TV viewing experience to the benefit of producers, distributors and consumers, provided the industry is careful to map parameters to the realities of human perception. Specifically, there needs to be general understanding with respect to the following points:

The requirements of live broadcast programming should be the threshold for setting HDR parameters:

  • Dynamic contrast and color ranges will have to deliver an optimal viewing experience without reliance on intervening post-production processes.
  • On-site production teams will have to incorporate understanding of HDR to ensure fidelity to creative intent.

The different rates of light and dark adaptation could play a significant role in quality of experience (QoE):

  • Light adaptation is fast. Dark adaptation is slower.
  • Mixed SDR and HDR could impact QoE for ad insertion, scene changes and program selection.
  • Bleaching adaptation could significantly slow adaptation to changes in program luminance.
  • Bleach fractions might begin to be significant at 1,000 cd/m.
  • They definitely will have an impact at multiple thousands of cd/m.
  • It might be beneficial to limit average scene luminance to low bleaching fractions.
  • It might be beneficial to limit the duration of high-luminance highlights to minimize after images.

Adaptation could impact user interaction:

  • Graphic overlays might need to be tailored to the expected light/dark adaption state.
  • GUI could easily be impacted.

HDR should not be considered in isolation. It impacts:

  • Color perception with implications for bit depth and color gamut
  • Sensitivity to flicker as a function of screen size, frame rate and display refresh rate

Sean T. McCarthy, Ph.D., is a Fellow of Technical Staff at ARRIS.

Get the Broadband Technology Report Newsletters Delivered to Your Inbox

Subscribe to email newsletters today at no cost and receive the latest information on:

  • Video Technology
  • Network Technology
  • Technology Alerts
  • BTR LATAM (Latin America)

SCTE-Cable Tec Expo 2016 Video Show Dailies

BTR's SCTE-Cable Tec Expo Video Show Daily, Day 3

BTR's SCTE-Cable Tec Expo Video Show Daily, Day 3

In our Video Show Daily for Day 3 of exhibits at SCTE Cable-Tec Expo in Philadelphia, BTR Editorial Director Stephen Hardy covers trends in distrib...

BTR's SCTE-Cable Tec Expo Video Show Daily, Day 2

BTR's SCTE-Cable Tec Expo Video Show Daily, Day 2

In our Video Show Daily for the second day of exhibits at SCTE Cable-Tec Expo in Philadelphia, BTR Editorial Director Stephen Hardy highlights furt...

BTR's SCTE-Cable Tec Expo Video Show Daily, Day 1

BTR's SCTE-Cable Tec Expo Video Show Daily, Day 1

BTR Editorial Director Stephen Hardy reviews the hot technologies and announcements from the first day of exhibits at SCTE Cable-Tec Expo 2016 in P...

Diamond Technology Reviews - 2016 High Scores

2016 Diamond Technology Reviews Slideshow

2016 Diamond Technology Reviews Slideshow

Diamond Technology Reviews 2016

Diamond Technology Reviews 2016

BTR's Diamond Technology Reviews, now in its twelfth year, is a technology recognition program wherein vendors serving the broadband cable ...

Related Articles

Cable ONE

2 More AZ Towns Get Cable ONE Gigabit

October 7, 2016

Cable ONE (NYSE:CABO) is expanding its GigaONE gigabit Internet footprin...


Comcast Launches Enterprise IoT Trial

October 6, 2016

Comcast (NASDAQ:CMCSA) announced machineQ, a business trial venture focu...


2016 SCTE Cable-Tec Expo Wrap Up

Whether you couldn't make it to Cable-Tec this year or want to see if you missed anything while you were there, you'll want to join BTR editors Stephen Hardy and Ron Hendrickson as they reveal their picks for the...

October 12, 2016
Sponsored by

Counting the cost: Efficiently transitioning from HFC to FTTH

HFC networks are uniquely positioned to provide compelling and competitive services, and are also uniquely positioned to transition to symmetrical FTTH as commercial requirements demand.  This webinar will d...

Date:September 22, 2016
Sponsored by

Maintaining High Quality of Experience in an Adaptive Bitrate System

This webinar will look at the many points in an ABR system where the video is touched.  From ingest (satellite, file, and IP), to egress, each point should be qualified for compliance to help maintain a high...

Date:August 25, 2016
Sponsored by

White Papers & Special Reports

Cable VoIP 2.0: Voice Moves to the Cloud

October 2016

Cable providers led the charge on the VoIP evolution and won customers and market share. Now voice networks are evolving again. The cloud voice platform has ...

Understanding Ultra High Definition Television

October 2016

Over the last 10 years, high definition television (HDTV) has been replacing standard definition television as the expected viewing format for television pro...

Are You Ready for DOCSIS 3.1? The Future of Cable Technology and How to Prepare Your Network

October 2016

DOCSIS 3.1 promises 10x capacity throughput and a range of technical benefits for cable providers and users alike. Are you ready? Discover the technical adva...

BTR Blogs

BTR Managing Editor Ron Hendrickson

FCC Rethinks Set-Top Plan

September 10, 2016

By Ron Hendrickson - The FCC has reworked the "unlock the set-top b...


In Memoriam: Richard Covell

August 18, 2016

By Rob Stuehrk, Publisher - We at Broadband Technology Report were sadde...

BTR Managing Editor Ron Hendrickson

Court Overturns FCC Municipal Broadband Order

August 11, 2016

By Ron Hendrickson - You win some, and you lose some, and the FCC just l...

Featured Hangouts

4K 4 U: How to Prepare for UltraHD Video

4K 4 U: How to Prepare for UltraHD Video

4K/UltraHD video is coming - consumers are buying the TV sets, and more content is becoming available. Watch this inf...

DOCSIS 3.1: A Look Ahead

DOCSIS 3.1: A Look Ahead

Watch a 30-minute video chat of experts from a variety of related disciplines discuss how close deployments really ar...

Featured Hangout

4K 4 U: How to Prepare for UltraHD Video

4K/UltraHD video is coming - consumers are buying the TV sets, and more content is becoming available. Watch this informative Hangout on demand by clicking the link above.

Sponsored by Verimatrix.