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Saturday, June 3, 2023

Why HDR Looks Too Dark on Your TV, and How to Fix It

Step aside, 4K: High Dynamic Range (HDR) is the most exciting jump in picture quality since the transition to HD, and it's available on more TVs than ever. But if you bring home your shiny new HDR TV only to find that shows are too dark to see, you might think there's something wrong—after all, isn't HDR all about brightness? Here's what's going on and what you can do to brighten the picture.

Why HDR Seems Dark on Some TVs

The movies and shows you've been watching for years were mastered in what we now call standard dynamic range, or SDR—and it's actually quite dim, mastered with peak brightness levels of only about 100 nits. Most modern LCD TVs, however, are capable of putting out 300 nits or more when playing that SDR content, so if you're in a brightly lit room, you can just crank up the backlight, which lifts the brightness of everything in the picture—from dark shadows to bright highlights.

HDR is different. Its main purpose is, as its name suggests, to create a higher dynamic range—that is, a bigger gap between the dark parts of a scene and the bright parts. In HDR, bright highlights can be 1,000 nits or more, depending on the capabilities of your TV. In HDR, a sun shining through the forest will really pop against the shady foreground, or a campfire will glow like an oasis of warmth against the dark desert night. On the right TV, this creates an incredible image, but it doesn't mean the entire image is brighter than its SDR counterpart—only those highlights are. The average brightness of the HDR scene should, in theory, be similar to that same scene in SDR (though this can vary from movie to movie, depending on how it was graded).

However, there's a problem: Many TVs default to the maximum backlight and contrast levels in HDR mode, so you can't crank them any higher for that well-lit living room like you can with SDR content. This isn't true of all TVs, but it is common, and it can leave you in quite a pickle.

Even worse, some TVs actually darken the image to make up for their HDR failings. "The light output of many value 4K HDR TVs is often no different than that of many non-HDR TVs," says Robert Heron, a professional TV calibrator and host of the AVExcel home theater podcast. This is most common on cheaper TVs, but it can happen with certain midrange or even high-end models that cut corners on brightness. Combine that with HDR's wider color palette, which many of these lower-performing TVs can't reproduce, and the TV has to do something to make up for its shortcomings.

When a TV can't reproduce those bright highlights at the specified levels, it performs a process called tone-mapping to fit the content to its capabilities. Say you have a lower-end TV that's capable of only 350 nits in HDR. When it plays a scene that has a 1,000-nit highlight, it has to adjust the scene so that highlight is only 350 nits. There are two main ways TV engineers approach this:

  • Some TVs will "clip" the bright highlights, keeping the average brightness of the scene where it is. The picture won't darken much, but the highlights may be a bit blown out.

  • Other TVs will lower the average brightness of the scene, preserving the detail in the highlights but making the overall image darker than it was originally mastered.

If your TV does the latter, good luck trying to watch that scene in a well-lit room. (You see this in action in this clip from HDTVTest—he's using high-end OLED TVs in that video, but the general principle can apply to cheaper TVs too, where the effect will be even more exacerbated.)

In other words, just because a TV can accept an HDR signal doesn't mean it's really capable of reproducing HDR properly, and your experience will suffer as a result.

How to Brighten the Image for Daytime Viewing

Alright, enough technobabble—you just want to be able to see your TV. Every set is a little different, but there are a few things you can try to make that picture brighter.

First, Heron recommends starting with the TV's firmware. "Verify there isn't an update that could address any known issues," he says. Especially on value-oriented TVs, firmware updates can have a drastic effect on picture quality. Sometimes it's an improvement, sometimes it's a downgrade—one of the reasons I leave my TV disconnected from the internet—so I recommend Googling around to see what other people have experienced with the latest firmware before you take the plunge. You might get lucky.

If that doesn't work, start playing an HDR movie or show—to put your TV in HDR mode—then open the TV's picture settings. Heron recommends starting from a blank slate, so reset the picture modes to their default. Then, try the following:

  • Turn up the backlight: You've probably already tried this, but if not, find the Backlight setting and turn it up. Note that you want to crank the Backlight setting, not the Brightness setting, which should almost always stay at its default value. Raising the brightness might brighten the picture a bit, but it'll also crush shadow detail. (Sony TVs are the exception, where the Backlight setting is labeled "Brightness.") Some TVs may not let you adjust the backlight any higher in HDR mode, but others will.

  • Adjust local dimming: Again, this setting is probably already set to its ideal level, but just in case, open your picture settings and play with the Local Dimming option (if your TV has one). Certain presets may dim the entire image to keep black levels as deep as possible, which is not necessary in a well-lit room.

  • Tweak your gamma: If your TV has a Gamma setting, it's likely set at 2.2 by default. Changing it to 2.0 or lower may help the picture appear brighter.

  • Change your picture preset: You've probably read TV guides that say you should put your TV in Movie or Cinema mode for the most accurate picture, and that's true—but this may look too dim during the daytime. "That preset is specifically optimized for dark-room viewing," says Heron, which is why some TVs have a "Cinema Home" mode that's brighter than the regular Cinema mode. In other cases, you may even want to go so far as choosing the Standard picture mode. The colors won't be as accurate, but it might counter the ambient light and make the picture look brighter.

  • Go back to SDR: Finally, if none of the above works well enough for you, there's one last-ditch option: watch your shows in SDR during the day. There's no shame in this—some would even argue that HDR is really meant for dark-room viewing anyway. If you can't get a bright enough HDR picture in your sunlit living room, go to the menu of your streaming box, head to its display settings, and turn HDR off. You can always switch it back to HDR on the occasions you're watching movies in a dark room and want the full effect. Or, at least, as much of the full effect as your TV is capable of.

Ultimately, you'll have to play with your settings and see what works for your TV in your room. If you can't seem to get it bright enough and you aren't satisfied with switching back to SDR, a professional calibrator may be able to help you dial in the picture for that brighter environment—though if you have a cheaper TV, you might be better off returning it and putting that money toward a more capable set. Heron notes that there are plenty of bright TVs out there, even if you're on a budget, so it rarely makes sense to settle for a lower-performing model. You shouldn't have to squint to see your shows.

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