HDR Calibration: What They Don’t Tell You

The reason production houses spend as much as $40,000 on reference monitors is quite simple: they need to have unwavering confidence that their work is going to be displayed exactly as intended. However, all displays change with time, and the only way to ensure consistent results is to calibrate them on a regular basis.* Yet, there is precious little literature on this vital step in the production process. As you’ll soon learn, there’s much more to it than simply plugging a calibrator into the USB port of your monitor!

Enter the PA32UCX-K, “the world’s first 32-inch 4K HDR monitor with peak brightness of 1,200 nits and mini-LED backlighting,” which I picked up solely in order to create HDR content for YouTube. The monitor is already pre-calibrated at the factory to ensure Delta-E (∆E) <1 color accuracy; each monitor sold comes with a detailed calibration report; an X-Rite i1Display Pro colorimeter is included in the box; and calibration software can be downloaded from Asus’ website. So we’re all good to go, right? Well, not exactly. You see, external monitors must be connected to a Mac via an I/O capture device – which in my case is the UltraStudio 4K Mini – in order to bypass the computer’s own color management. The typical chain would work in any post facility as follows:

Workstation/Mac -> UltraStudio via TB3 -> Calibrated Monitor via HDMI or SDI

The display in the chain is usually an industry-accepted broadcast monitor like the FSI or TVLogic.  In this case, we’re replacing it with an Asus ProArt monitor, which costs less and does more. Typical broadcast monitors only accept video signals and cannot be used as an extension of your computer desktop/workspace – they’re purely for video signal preview only. The Asus supports multiple inputs and can be used as a desktop extension monitor.

However, the UltraStudio 4K does not have any calibration capabilities. It is a professional I/O box which allows output of SMPTE & broadcast compliant video signals to external monitoring devices. It is important not to allow the PC/Mac OS to manage the color on the video output to the Asus if you want an accurate preview of the colors you have. Hence there is the UltraStudio serving as an I/O bridge between the iMac and the monitor.

Regarding calibrating with an external calibrator like the X-Rite, this is software managed, and is only ideal for getting your desktop displays accurate; however, there are some variances due in part to external light and ambient light sources. To the best of my knowledge, the only solution at hand is Blackmagic’s recently announced Teranex Mini SDI to HDMI 8K HDR ($1,600.00 in Vietnam). This is essentially a broadcast converter; however, it features an onboard calibration engine which works with the X-Rite calibrator via USB.

Remember, natively the X-Rite calibrates the computer desktop environment via their software and this is to calibrate the VGA signal from the computer out to the computer displays. You won’t be able to use this to calibrate any monitors not connected to the computer via traditional computer VGA ports like Display Port, DVI or HDMI. This is simply because it relies on the computer managing the display colors. Once you use an UltraStudio or any broadcast standard video I/O device, you won’t be able to calibrate the preview monitor connected to these I/O devices because the computer no longer manages the colors being displayed.

However, with the new Teranex Mini SDI to HDMI 8K HDR, there is a built-in calibrator and a USB port on the device – all you need to do is connect the X-Rite to the Teranex Mini, run the calibration engine via the device menus, follow the onscreen instructions, allow the Teranex Mini to read the color profile of your connected monitor and when it’s done, the Teranex Mini will generate a broadcast-accurate 3D LUT for that device, store it onboard, then apply it to the HDMI output to the connected display. The chain would look like this:

iMac -> UltraStudio 4K via TB3 -> Teranex Mini SDI to HDMI 8K HDR via SDI -> Any HDMI Device via HDMI.

Why is it so complicated?  Well, if the post facility can afford broadcast standard SDI monitors costing more than a Tesla, then it’s all fine, they just need the UltraStudio 4K. However, if the post facility is just a new start-up with limited funds, or if it is a case of a freelancer who is just setting up his own studio with limited funds, it would be impossible to justify spending USD $6,000 on an FSI SDI monitor that does nothing more than display a video preview although it is broadcast accurate. So the next best solution would be to add a Teranex Mini SDI to HDMI 8K HDR into the chain and then connect any available decent quality HDMI monitor or even large TV to the chain to be used as an output preview device.

“This all sounds so complex,” you might be saying, “wouldn’t I be better off going with the Pro Display XDR?” Well, even with Apple’s gorgeous 6K monitor, you aren’t guaranteed broadcast accurate colors. This is because the MacOS is still managing output display colors which are not SMPTE compliant. Although boasting very high specifications, there is no mention anywhere of it being calibrated to SMPTE specifications, or that the MacOS is able to output SMPTE compliant video signals.

There are  of course production facilities planning to purchase the XDR display, but they still have the UltraStudio in their device chain connected to a Sony X300 Broadcast Master Monitor, purely for HDR preview and mastering. This SDI monitor alone runs in the neighborhood of USD $35,000. HDR really is the wild west, so unless a post facility is generating revenue from high-end work, it’s advisable to keep things simple. Once you start wanting to get everything HDR ready properly, the investment is going to be insane.

My takeaways? HDR is a bottomless pit. It’s also endlessly fascinating. Being able to view my Final Cut Pro timeline in HDR on the Asus is a trip. Once you’ve seen shows like the brilliant documentary Chef’s Table or the superb television drama Sense8 on an OLED display, you’ll be clamoring for more HDR content. Would I recommend picking up a $4,000 HDR monitor though? My advice for those who, like me, just want to produce content for YouTube, would be to wait until next year, when there should be several affordable mini-LED HDR1000 laptops on the market.

And for those really interested in monitors in general as well as in calibration, here’s an informative podcast with Bram Desmet, CEO and General Manager of Flanders Scientific.

* Under continued use, a monitor’s white color temperature and brightness change gradually over time. Assume a monitor’s color temperature was set to 5,000 K and its brightness to 100 cd/m² when purchased. Since these values will change with time under continued use, a few months later the white will have become warmer and the brightness will have dimmed, to 4,500 K and 90 cd/m² , respectively. For this reason, calibration is important to return the monitor to its   original state—i.e., to a color temperature of 5,000 K and a brightness of 100 cd/m². When using a monitor for graphics, stable color can be maintained at all times by conducting calibration at a frequency of once every 200–300 hours. An LCD monitor used for graphics should be calibrated at least once every 200–300 hours (in ordinary use, once per month) – Eizo