Why Your HDR Monitor is (Probably) Not HDR at All – and Why DisplayHDR 400 Needs to Go

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Marketing a display as supporting HDR (High Dynamic Range) is becoming increasingly common in the monitor market with most new displays talking about how great HDR is, and the benefits it offers on spec pages and press releases. The problem is, the general “HDR” label is so open to interpretation and so open to abuse, that it’s very difficult for an average consumer to really know what is being offered from any given screen. They see the HDR label and assume that’s all they need, when in fact there are many different levels of actual HDR performance from a display. Despite some groups such as VESA trying to develop a certification scheme to take control of this and develop some standards, it hasn’t really helped as their scheme is flawed by the lower grade certifications which are just as equally open to interpretation and abuse. We wanted to write this article to hopefully raise more awareness, and also to make a plea to VESA to reconsider its entry level HDR certifications. Is your HDR display really HDR? Read on to find out.

Introduction

We aren’t going to go in to detail about exactly what HDR is in detail here, you can read about High Dynamic Range, it’s benefits, how it improves multimedia and gaming images and how HDR is made possible from a display in our in depth article. As a brief summary though, HDR is primarily about producing a higher dynamic range (as the name suggests) in content, that being more specifically an improved active and visible contrast ratio to the image. This is a larger range between the brightest whites and the darkest blacks visible at any one time on the screen. Second to this improved active contrast ratio, the HDR term has also been linked in the display market with providing a boost in the screens colours beyond the normal sRGB colour space most screens offer, usually through the use of a wider colour gamut backlight and a 10-bit colour depth panel. So for a screen to offer any kind of HDR support it at least needs to be capable of producing an improved active contrast ratio and offering a boosted colour performance. The problem is that not all HDR-marketed screens actually offer this. We want to try and help you spot screens which have no real or meaningful HDR capabilities, or have “fake HDR” here if we can.

“HDR input support” or “HDR10 support”

This is one of the most common marketing ploys used by display manufacturers, and reminds us a little of the early days of “HD ready” TV’s – those could accept an HD signal but lacked the necessary resolution to really display it properly! Saying a screen can “support an HDR input” or accept an “HDR10 source” is largely meaningless and something we feel is quite misleading for consumers. Being able to accept an HDR input signal is all very well, but the screen needs to be able to properly produce an HDR output as well. We have seen many displays released and marketed for HDR when they lack the necessary ability to produce higher dynamic ranges or anything approaching HDR. Other attempts to mislead consumers like creating proprietary HDR badges and naming schemes may also be found in the market, but again are offering no real HDR performance from the display. If you see these terms listed for a monitor, be wary, they probably aren’t truly offering any HDR experience unless they also carry a proper certification or provide more details in the specs (talked about later in this article).

VESA have at least taken a lead in producing a certification scheme to classify desktop monitors when it comes to their HDR capabilities through their ‘DisplayHDR’ levels. This has included input from more than two dozen participants including AMD, NVIDIA, Samsung, Asus, AU Optronics, LG.Display, Dell, HP and LG for instance. There are DisplayHDR certifications for 400, 500, 600 and 1000 for desktop LCD monitors, with a couple of others introduced for future OLED displays too. This VESA certification scheme does help a bit, as if you see a monitor advertised nowadays which talks about HDR in any way, but doesn’tthen talk about the relevant VESA DisplayHDR certification then you should consider that a red flag straight away.

VESA Display HDR Certifications

The VESA scheme, in naming at least, is largely linked to a display’s maximum peak brightness capability with each number representing the backlights max brightness spec. For example VESA DisplayHDR 400 is for screens which can reach 400 cd/m2 peak brightness, HDR 600 for those that can reach 600 cd/m2 and so on. Peak brightness is pretty important for an HDR display, as you need to be able to produce brighter highlights and more lifelike bright images to improve the overall experience. However, being able to make an image brighter is pointless if you can’t then also make other areas of the screen darker at the same time. The whole point of HDR is to actually improve the dynamic range (active contrast ratio). The actual peak brightness requirement to create a decent HDR display is somewhat debatable, perhaps even more so in the desktop monitor market. Some might consider 1000 cd/m2 peak brightness the bench mark because a lot of content is mastered to those levels and because it’s become quite common in the TV market, but others may actually prefer something a bit more modest like 600 cd/m2. It can depend on the viewing position, ambient light conditions of the room, the content being viewed etc. Some users may not want a display that outputs 1000 cd/m2 from up close for gaming. Higher peak brightness doesn’t necessarily mean a better HDR experience and isn’t that important when you come to consider a screen’s HDR capability. What is important though, without question, is the screens ability to improve the active contrast ratio. To do that, you NEED to have some kind of local dimming support from the backlight.

http://www.tftcentral.co.uk/images/dell_up2718q/384-zone.jpg

Local dimming is enabled by the monitors backlight, where it is divided up in to a number of separate backlit zones. This allows certain regions of the screen to be made brighter while at the same time other regions are made darker. This local dimming is what creates the actual improvements in contrast ratio and dynamic range on the screen. The more local dimming zones there are, the better the HDR capability in theory as the screen can control the highlights and low-lights in a more precise manner. On OLED TV’s this is done at a pixel level and one of the reasons why OLED is so popular for HDR content right now. For LCD’s it needs the backlight to be split in to zones so has a less finite control over the image area. Local dimming is vital to create any real improvement in the dynamic range of an image, and it is the support (or lack of in many cases) local dimming that is the main issue here.


VESA DisplayHDR 400 Needs to Die!

Even where the certifications are used, the problem with the VESA DisplayHDR scheme is that the entry level is, in our opinion, a waste of time. The scheme is also set up in a way that an average consumer might only assume that all levels offer an HDR experience, just with a different peak brightness (400, 500, 600 and 1000 cd/m2). They may not realise that beneath those certification levels, they also have different requirements when it comes to other more important measures of what makes for a meaningful HDR experience.

Our main concern lies at the lower entry-level end of the VESA scheme – the “DisplayHDR 400” standard. This we consider to be a very weak classification that has already encouraged shoddy, misleading marketing from display manufacturers. The whole point of the VESA certification scheme was to avoid misleading consumers about a screens HDR capability, but we feel that this entry level HDR 400 badge achieves the opposite. You will see it slapped on nearly every new display emerging, making consumers believe it offers an HDR experience (after all, it has the approved badge, right?), when in reality it doesn’t offer them anything meaningful or useful. In many cases the screen carries the badge, but lacks all the basic fundamental requirements that would constitute an HDR experience we talked about earlier!

Maybe it’s the display manufacturers who have pushed VESA for this entry level point, allowing them to market their screens as HDR certified to hop on the band-wagon of the hot topic right now? The HDR 400 badge is in our opinion misleading, and we don’t feel it really delivers much beyond what can be achieved from most displays available in the market already – even before the advent of HDR. It’s not much more than a label to say the screen can accept an HDR input source, but can’t produce any meaningful HDR output from the display itself! We will explain….

If you look at the low end DisplayHDR 400 standard in any detail you realise that its requirements are very loose, and not really in line with providing any meaningful HDR experience. To earn the HDR 400 badge a display needs only offer:

  • Peak brightness of at least 400 cd/m2 – this isn’t actually much beyond what a “normal” screen can offer, which are typically 300 – 350 cd/m2 anyway. It’s also nowhere near the higher peak luminance that the main HDR10 and Dolby Vision (and other) content is mastered to.
  • Global dimming – this is where the entire screen is brightened or darkened all in one go depending on the viewed content. This is the same as the old “Dynamic Contrast Ratio” technologies of years gone by, which fell out of fashion about 5 years ago as no one really liked it or used it! Global dimming won’t improve the contrast ratio experienced on the screen at any given point in time, as the whole screen is being dimmed or brightened in one go. You are limited by the screens normal static contrast ratio, typically around 1000:1 for a TN Film or IPS panel, but typically around 3000:1 from a VA panel. The global dimming doesn’t help achieve any higher contrast ratio (or high dynamic range) compared to a normal screen though. Most people don’t like the appearance of dynamic contrast ratios either, and the way it changes the backlight brightness up and down.
  • Colour space / colour gamut – they only require 95% of the ITU-R BT.709 colour space, basically 95% sRGB which again is the norm on nearly every display around now. No requirement to actually offer the wider colour gamut associated with HDR content and an improved viewing experience.
  • Colour depth – there is a requirement for a true 8-bit colour depth, which at least rules out some of the 6-bit+FRC panels on the market. However, most normal screens nowadays are 8-bit anyway, so this doesn’t really require any improvement over those normal models. A 10-bit colour depth is really required to support the colours of HDR content, and that’s not a requirement for a screen to earn the HDR 400 badge.

As we said earlier, local dimming is VITAL for the production of an improved dynamic range from a display, and it is the lack of this which really hampers the HDR 400 certification level. Without local dimming of any sort, we don’t feel a screen should be marketed as HDR to be quite honest. Global dimming doesn’t count. To earn the HDR 400 badge the screen doesn’t actually need to offer any improved dynamic range, doesn’t need to create a brightness much higher than a normal display and doesn’t need to offer better colours either! What’s the point then? Sometimes you might see a boost in the colours through a wide gamut backlight on an HDR 400 certified screen, but even that is sometimes hard to spot from the marketing material and not something your average consumer would necessarily know to look for. They want to see an HDR label and have faith that they will get an HDR experience of some sort from the display – that seems a reasonable expectation to us.

Labeling a screen as supporting HDR through this HDR 400 certification is meaningless and misleading we feel. We would love to see this level either dropped or revamped to a more useful standard if it is to continue to be used. Please help bring some order back to the HDR monitor market VESA!

The Other Levels Are Better Thankfully

The DisplayHDR 500, 600 and 1000 certifications are better thankfully, and getting in to the realms of what we would consider meaningful HDR. DisplayHDR 600 requires a 600 cd/m2 peak luminance which is a decent step up from common displays and can provide an improved peak luminance for HDR content. They are also pushing colour depth requirement of the display to 8-bit+FRC (10-bit support), colour gamut requirements are boosted to 90%+ of the DCI-P3 coverage, HDR contrast ratio requirements up to at least 6000:1, and importantly the 600 certification details the need for local dimming implementation. Even if this is only edge lit local dimming in a limited number of zones, that’s still an improvement over “Global Dimming” from the HDR 400 level and should offer improved active contrast ratios relative to a non local dimming display. It also helps by bringing it more in line with the standards used in the TV market and producing that colour boost that HDR is associated with.

Then at the top end the DisplayHDR 1000 certification pushes things a bit more and aligns closely with the “Ultra HD Premium” standards used in the TV market for similar purposes of certification. A 1000 cd/m2 peak luminance is now needed, along with >20,000:1 HDR contrast ratio, 10-bit colour depth support (at least 8-bit+FRC) and 90%+ DCI-P3 colour space coverage. Again all requiring local dimming. We expect that most models that can reach these kind of peak luminance levels will need Full Array Local Dimming (FALD) backlights with hundreds of dimming zones as well, which adds another level of improvement, although it’s not a specific requirement in the certification scheme.

As another interesting note, the 600 and 1000 certifications also define a “black to white luminance response time” which is again not needed for the HDR 400 level. This is not related to pixel response times in the traditional sense, but defines how fast the backlight should behave when going from a black image to a white image. i.e. how long it takes from going from minimum luminance of a dark HDR scene to the peak luminance of a white patch when it appears. This helps ensure there is no annoying lag with the image being dimmed and brightened at the wrong time or producing a lot of blooming behind moving objects.

So overall we are more comfortable with the HDR 500, 600 and 1000 standards as they at least define the requirements for local dimming, an improved contrast ratio and improved colours. What then constitutes “true” HDR is another debate, but at least a screen with these capabilities will offer you improvements over a standard display and give you some level of meaningful HDR experience.

Conclusion

If you’ve got a screen which promotes HDR but lacks any kind of VESA certification, there’s a very good chance that it offers no real HDR experience. You’d have to delve in to the product specs to understand what it does or doesn’t offer in terms of local dimming, extended colour gamut, colour bit depth etc. Chances are, there’s nothing meaningful being offered and it might be hard to tell unless the manufacturer provides specific details.

Beyond that if you see the VESA badges being used, we would recommend ignoring the HDR 400 badge altogether and would much rather it didn’t exist. At least in its current form. A VESA DisplayHDR 400 certified display isn’t offering you any real HDR benefit at all. Maybe you will get a slightly brighter image than a normal display, and maybe the manufacturer has bothered to add a wide gamut backlight to at least improve the colours a bit. However, they don’t have to do that to earn the HDR 400 badge, and in reality there’s no improvement to the dynamic range from screens which currently carry this certification.

If the screen has one of the higher certifications (500, 600 or 1000) then you will enjoy some level of HDR benefit, and at least should expect an improved contrast ratio thanks to the local dimming backlight, and some boosted colours too. It might still be hard to identify in some cases the level of local dimming (how many zones etc) but at least these offer something in the way of HDR performance. HDR 600 and 1000 displays are still fairly rare, with the HDR 400 models being far more prevalent unfortunately.

For more information about HDR, see our in depth article recently updated


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