Calibrating Ultra HD 4K Displays

May 19, 2014

The author’s custom CIE chart.
You’ve heard a lot about 4K lately but, if you’re an integrator, you’re probably wondering what it means for business. Ideally, newer technology with a fancy buzzword means more sales opportunities, but what does it mean in terms of setup and calibration?

4K, or Ultra HD as it is more accurately referred to, is currently in a state of transition. We’re seeing the first roll out consisting of displays including nothing more of the Ultra HD specification than the higher resolution of 3840x2160; there isn’t an enhanced color gamut, HDMI 2.0 is not included, and the matrix for properly processing the new ITU-BT.2020 Ultra HD standard is missing. Essentially, the first set of Ultra HD displays are up-converting Rec.709 HD displays. So what does it mean for calibration?

You may remember that our standard-definition system is specified by the International Telecommunications Union, or ITU, as ITU-R BT.601, in short it is the ITU’s recommended standard for broadcast television document number 601. When we moved to HD, we had ITU-R BT.709, and as we transition into Ultra HD, we now have ITU-R BT.2020. Each document specifies things like system colorimetry, signal formats, frame rates, color matrix, bit depth, resolution, sampling lattice, pixel aspect ratio, and even how the pixels are addressed–it’s left to right and top to bottom if you must know.

Of note, Ultra HD comes in two resolutions– 3840x2160 and 7680x4320, allowing for higher resolution than what is available today. Additionally, it is currently specified in 10- and 12-bit formats, a significant improvement over the traditional 8-bit system we’ve been accustomed to in the consumer world. What does this mean? It means that instead of having 254 shades of gray, we’re able to have 1,016 shades in 10-bit and 4,063 shades of gray in the 12-bit system; of course, this is if you are utilizing the full range signal, which not everyone does.

I mentioned that the Ultra HD BT.2020 specification provided the system colorimetry. Well, that has been significantly increased over the BT.709 specification. In fact, you can see the difference between BT.601 (SD SMPTE-C), BT.709 (HD), and BT.2020 (UHD) in the chart provided. Notice the white reference is still located at the same D65 point of x = 0.3127 and y = 0.3290. The coordinates for system colorimetry are illustrated in the graphic on this page.

While this color specification accommodates a significant amount of additional color, many don’t believe it will be completely feasible with the majority of technology currently available do to their ability to hit a color target located at the spectral locus. To date, we have not seen, nor has anyone claimed, that they hit the specified color gamut in their display for BT.2020. There are a few products in the works, some may be introduced later this year. Even broadcasters are searching to acquire displays capable of hitting the BT.2020 targets, so that they can start mastering content. Sadly, everything that is mastered is often mastered for BT.709 do to the formats and technology that are currently available.

So how should you approach the calibration of an Ultra HD display? The answer is complicated yet simple. With today’s displays and program material, you would optimize for BT.709 and the BT.1886 gamma target (approximately 2.4). As the technology improves and content is made available in the Ultra HD format, you would target the BT.2020 standard. Of course, if the display system isn’t capable of hitting BT.2020, you would target an emulation mode. What is an emulation mode? Well, emulation modes are often used in content creation where a display isn’t quite capable of hitting a specification, such as the Digital Cinema P3 Color Specification, so we calibrate to a mode that is closest to the target. To do this, the red, green, and blue primaries are a point on the target color gamut’s triangle, not inside, or outside; you get as close to the target on the line as possible while maintaining the target white point.

As displays improve and Ultra HD content is delivered to the home, calibrating to the new standard will be of utmost important to ensure accuracy. For now, calibrating to the HD standard will allow for accuracy of current 4K content that is BT.709 content provided at a higher resolution.

David Abrams (dave@avical.com) is president of Avical, a Los Angeles-based audio/video calibration and consulting company. Follow him on twitter @AvicalTweets or on Facebook at www.facebook.com/Avical.Inc

Want to read more stories like this?
Get our Free Newsletter Here!

Comments

Photo GalleriesMore Galleries >
Doug Henderson and Joe Atkins

Doug Henderson (left) president of Bowers & Wilkins Group North America, and Joe Atkins, Bowers & Wilkins global CEO, invited consumer and t...

BMWs, McLarens, and Volvos

Upon arrival, guests experienced Bowers & Wilkins Automotive products in BMW, McLaren, and Volvo cars (the Maserati wasn’t available...

Demo'ing the McLaren

Bowers & Wilkins North America president Doug Henderson show demonstrates how to open the door on the McLaren.

B&W Speakers in the McLaren

Bowers & Wilkins speakers in the McLaren.

B&W Vintage Living Room

Bowers & Wilkins North America president Doug Henderson shows off the company’s vintage living room space, which featured vintage ge...

The B&W LP Collection

Part of the Bowers & Wilkins vintage living room space is this collection of LP covers that represent a seminal album from each of the com...

The B&W Museum

Bowers & Wilkins had to purchase much of the gear in its museum because most discontinued products were not kept over the last 50 years.

The Wisdom of John Bowers

Words to live by from Bowers & Wilkins founder John Bowers

The History of B&W

A timeline of Bowers & Wilkins’ product and company history

Andy Kerr and Martial Rousseau

Senior product manager Andy Kerr and head of research Martial Rousseau from the U.K. Bowers & Wilkins office. They were showing off the ne...

Turbine Head

  The turbine head for the 800 D3 houses the mid-range speakers.

Andy Kerr

Senior product manager Andy Kerr holds up the very heavy solid-body turbine head.

Historical Flagship Products

A look at the company’s flagship products through its 50-year history

The Legendary Diamond Tweeter Dome

To show off the company’s legendary diamond tweeter dome, one was encased in plastic to protect the brittle material. The tweeter domes ...

Demo'ing the 800 D3 Speakers

Bowers & Wilkins’ new demo room showcases its new flagship 800 D2 speakers, which are the outcomes of one of the company’s mos...

800 D3 Close Up

The silver 6-inch FST midrange drive unit of the 800 D3 uses Bower & Wilkins’ new proprietary Continuum woven material. Developed af...

In-wall Demo

Bower & Wilkins’ showcases its in-wall speakers in this space.

The B&W Nautilus

Bower & Wilkins’ legendary Nautilus is 17 years old but just as contemporary now as it was then.

Nautilus Pricing

A wall plaque in the “Nautilus demo room” itemizing the price of the system

Theater Demo

A theater demo showcasing the flexibility of 800 D2 speakers