Greetings from the high-speed Thalys train that links Amsterdam to Paris. I begin writing this as I return from IBC, the biggest and best video trade show in Europe.
This post addresses two dominant themes on the show floor and in the conferences: HDR, or High Dynamic Range, and the expanded color space of the Rec 2020 standard, or, simply put: more color and more contrast!
Dolby Vision presentation of resolution, fps, dynamic range and color-space image attributes at IBC
1. Two years later
2. HDR and Rec 2020 at IBC
3. Nits and ST 2084
4. Cameras in 4K and more
5. 14 stops
7. TVs and monitors
8. Theaters challenged
1. Two years later
Two years ago I wrote a post about IBC entitled 4K and Better Pixels, in which I detailed the following attributes of the digital signal as keys to improving the technical quality of images:
1. ”4K” Resolution
aka 3840 x 2160 - UHD for television
or 4096 x 2160 - 4K for cinema
2. High Dynamic Range - aka HDR
3. Increased Color Space - aka Rec 2020 aka ITU-R Recommendation BT.2020
4. High Frame Rate - aka HFR, proposed 48, 60 and 120 fps capture & display
5. Bit Depth - 10- to 12-bit is the new norm, with hopes for 16 bits in the future
6. Better Compression - like the proposed HEVC codec, aka H265
Briefly, the situation two years later is:
1. The new resolution standards of 4K for cinema and UHD for television are widely accepted as the future norms, but it's not clear how long the transition from 2K cinema projection and HD television will take. A lot depends on the amount of 4K films and UHD shows.
2. and 3. Many at IBC 2015 were pushing for HDR, an increase in dynamic range, in conjunction with the expanded color space defined by the Rec 2020 spec, which is proposed to replace the current DCI P3 digital projection standard.
4. Most modern cameras allow for HFR (high frame rate) of up to 120 fps, and sometimes more. HFR has found a niche in television, especially for sports. At present, HFR has not been widely accepted for cinema projection -- mainly because of the negative reactions to the 48 fps 3-D versions of the last two Hobbit films -- but the jury is still out. There are passionate HFR proponents like James Cameron and Douglas Trumbull, and new motion blurring technologies may make HFR cinema more popular.
5. ACES technology with 16-bit signals offers a post-production standard with lots of breathing room for color and contrast. Some, however, were cautious about 16 bits, as increased bit-depth can require the costly modification of pipelines and storage in existing “legacy” hardware and workflows.
6. Compression remains an unsolved problem, as the increased bandwidth for 4K and High Frame Rate exceeds the economy of current compression technologies.
2. HDR & Rec 2020 at IBC
HDR and the extended Rec 2020 color space were major themes of the IBC Conference. Moderators Robert Kisor and Julian Pinn gathered a number of knowledgeable presenters in four sessions to speak about HDR, including: Bill Baggelaar – Sony; Curt Behlmer – Dolby; Brian Bonnick – Imax; Curtis Clark, ASC; Dominic Glynn - Pixar; Stijn Henderickx – Barco; Pete Ludé – RealD; David Monk – EDCF; Kate Morrison-Lyons – Fluent Image; Oliver Pasch – Sony; Rick Sayre – Pixar; David Schnuelle – Dolby; and Jeroen Schulte – ILM.
Several presenters stated that Rec 2020 Color and HDR were low-hanging fruit; they averred that HDR and Rec 2020 would have a visible impact on television imagery without too great a cost or effort. Notably, existing cameras and workflows can deliver HDR without additional cost. However everyone recognized that HDR is difficult to achieve in cinema theaters.
Comparison of 3 color space triangles:
- smallest is Rec 709,
the current video standard
- medium is DCI P3,
the current digital projection standard
- largest is Rec 2020
It’s important to note that while there were many examples of Rec 2020 and HDR in video monitors on the show floor, there was no implementation of HDR in cinema projection at IBC. On the other hand, Barco’s 6P dual-projector system was used to demonstrate a 2020 color space on the big screen, with a screening of Pixar's Inside Out.
3. Nits and ST 2084
The unit for HDR is the nit. As a reference, the 14 foot-lambert theatrical screen brightness standard is equal to 48 nits.
Curtis Clark, ASC (Credit: Benjamin B)
In his presentation Curtis Clark stated that the general contrast range for current DCI DLP projectors was 2000:1. He cited the following numbers for SDR (standard dynamic range):
-- Film and digital cinema - 17 to 48 nits
-- Video monitors & television – 75 to 250 nits
Curtis pointed out that current Xenon DCI 3-D projection systems are limited to 17 nits, instead of 48.
While there are many existing transfer functions or LUTs for SDR, Curtis explained that the new SMPTE ST 2084 transfer function (aka Perceptual Quantizer or PQ curve) enables the display of HDR.
ST 2084 is designed to represent a range from 0 to 10,000 nits, using either 10-bit or 12-bit encoding. As an everyday reference, 10,000 nits is the brightness of an ordinary fluorescent tube.
The ST 2084 standard was designed to be roomy; at present no 10,000-nits monitors exist. While Rec 2020 is a published standard for color space, there is no practical norm for HDR, and different presenters gave different threshold numbers for what constitutes HDR in television and film; these ranged from 400 to 1,000 nits.
The BBC and NHK are developing their own standard, distinct from ST 2084, which is called Hybrid Log Gamma, and is designed to work well with both standard and HDR television sets.
Curtis added that "HDR, in conjunction with wide color gamut and greater image resolution provides filmmakers with a new creative canvas that expands the aesthetic possibities for visual storytelling".
4. Cameras in 4K and more
For cameras, the resolution standard is clearly now UHD and 4K. Although Arri’s Alexa and Amira cameras have a 2.8k sensor, the latest models offer in-camera up-resing to ProRes UHD or their version of 4K Cine (4096 x 2160).
New cameras are also proposing even higher resolution, and formats larger than Super 35, notably:
-- The Alexa 65, unveiled last year at Camerimage, which offers 6560 x 3100 in Open Gate mode
-- The Red Weapon, unveiled this year at NAB, which has an 8192 x 4320 sensor, slightly wider than full-frame 35mm still cameras.
The emergence of large-format cameras also requires appropriate lenses, like Arri’s Prime 65 series (based on the digital Hasselblads), Panavision’s Primo 70s and Zeiss’ Compact Prime CP.2 lenses. Interestingly, the Alexa 65 at IBC had a 1.25 de-anamorphosis setting for use with Panavision's Ultra 70 lenses in 2.39 ratio, the configuration that Greig Fraser, ASC, ACS, is shooting the new Star Wars movie with.
Colorfront's Aron Jaszberenyi wrote me to say that new tools they have developed may enable a resurgence of HFR (high frame rate) filmmaking. He says that the idea is to shoot HFR with a wide open shutter, and then "interactively set motion blur in post by blending multiple frames together." Aron also mentions that Ang Lee's upcoming film Billy Lynn's Long Halftime Walk, with cinematography by John Toll, ASC, was entirely shot in 3-D at 120 fps.
5. 14 stops
For the past century, the dynamic range of film negative has greatly exceeded that of print-film projection. The same is true of modern digital cameras. Depending on whom you ask, and how you measure dynamic range, cameras like the Arri Alexa, Canon C300, Panasonic Varicam, Red Dragon and Sony F65 offer a range of 12 to 15 stops, and Curtis Clark mentions 14-plus stops for 35mm negative, yielding a formidable contrast ratio of 16,000 to 1.
The challenge of HDR is to be able to show this range of dark blacks and brilliant whites on the set, in postproduction and to the viewer.
Curtis emphasized the importance of the ACES post-production standard, "as a comprehensive color encoding and color management system that effectively protects and preserves both HDR and wide-gamut color images. ACES ultra-wide gamut color space, along with its dynamic range of over 30 stops, provides plenty of head room for 'future-proofing'."
Rick Sayre from Pixar and Joeren Schulte from ILM gave a presentation about applying HDR and Rec 2020 Color in the feature film Tomorrowland, directed by Brad Bird, with cinematography by Claudio Miranda, ASC. The film was shot in 16-bit Sony raw at a 4K resolution using F65 and F55 cameras.
The filmmakers used a 2K Dolby PRM 4220 monitor at 600 nits during postproduction. The signal used was 12-bit 444 RGB, set in the P3 color space using the 2084 curve. Sayre pointed out that the white point is a matter of choice, and that they selected D65.
7. TVs and monitors
Clearly, one of the intentions behind the push for HDR and Rec 2020 is to help motivate consumers to buy 4K televisions by showing them dazzling images. Peter Sykes, Sony’s strategic technology development manager, told me that he believes consumers will appreciate the deeper blacks, brighter highlights and higher saturation of Sony's new line of HDR Bravia televisions.
Cinematographer Geoff Boyle, founder of CML, commented that until HDR monitors appear on set, the director of photography has to previsualize HDR images while shooting. “It’s just like film that way.”
Canon, Dolby and Sony presented professional monitors at IBC. Sony’s pro HDR monitors include the 30” OLED BVM-X300, which supports both ST 2084 and Rec 2020.
Hideyuki Komatsu, Canon’s general manager of display products, proudly showed me a prototype 30” 4K professional monitor with an amazing peak luminance of 2,000 nits. “Our ambition," said he, "is to be number one in HDR.” Canon also showcased a smaller 400-nits monitor for the set.
8. Theaters challenged
As mentioned above, there was no demonstration of HDR projection in IBC's Big Screen auditorium. Indeed, Pete Ludé from RealD, David Monk, and David Schnuelle from Dolby gave a fascinating presentation explaining the complex task of achieving HDR in theatrical distribution. Much of the difficulty lies in controlling stray light and reflections to achieve true deep blacks. Ludé noted that viewers' faces and clothing bounce back light, and joked that best results would be achieved with an empty theater, "although I haven't found the business model for that yet."
Dave Schnuelle - Pete Ludé - Dave Monk (Credit: Benjamin B)
An IBC screening of the animated feature Inside Out made a convincing case for trying for HDR and Rec 2020. The Barco 6P dual-projection system delivered high contrast and strong, saturated colors, especially in the highlights.
Several presenters evoked Dolby Vision, a new initiative to create dark theaters with top-notch projection and Atmos sound. At present, there are a handful of such theaters, but the hope is that future audiences will search out quality projection and be willing to pay more for a premium experience.
Several commentators pointed out that at present, high-quality televisions have more contrast and color than theaters, with the same resolution. There is, of course, a completely different viewing experience when you are watching a movie on a giant screen with a big audience. However, I left IBC feeling that cinema may have to renew its technology to offer image quality that surpasses the home screening.
- New Digital Image Standards
thefilmbook: IBC: 4K and Better Pixels
- 4K DCI
wikipedia: DCI 4K spec
thefilmbook: My post on Super High Vision 8K
- ITU Rec 2020 expanded color space spec
wikipedia: Rec 2020
dot.color.com: color space
dot.color.com: Rec 2020 color space
- SMPTE 2084 spec aka "PQ curve"
- Nits and HDR (high dynamic range)
- HFR (high frame rate)
thefilmbook: Douglas Trumbull - Temporal Continuity
thefilmbook: Douglas Trumbull - Future Movie Theaters
thefilmbook: Douglas Trumbull - Future Filmmaking
colorfront: download video demo of variable motion blurring (230 MB)
- ACES (Academy Color Encoding System)
oscars.org: ACES page
www.ooyala.com: 4kuhd tv shipments- q1-2015
thefilmbook: IBC: Digital Anamorphic
thefilmbook: IBC People: A Photo Album
Please don’t hesitate to give me your corrections via email or in the comments below. And, as always, your comments are also welcome.