Step apart, 4K: Excessive Dynamic Vary (HDR) is probably the most thrilling soar in image high quality for the reason that transition to HD, and it is obtainable on extra TVs than ever. However in case you convey dwelling your shiny new HDR TV solely to seek out that exhibits are too darkish to see, you may suppose there’s one thing fallacious—in spite of everything, is not HDR all about brightness? This is what is going on on and what you are able to do to brighten the image.
Why HDR Appears Darkish on Some TVs
The films and exhibits you have been looking ahead to years had been mastered in what we now name customary dynamic vary, or SDR—and it is truly fairly dim, mastered with peak brightness ranges of solely about 100 nits. Most fashionable LCD TVs, nonetheless, are able to placing out 300 nits or extra when enjoying that SDR content material, so in case you’re in a brightly lit room, you possibly can simply crank up the backlight, which lifts the brightness of all the things within the image—from darkish shadows to shiny highlights.
HDR is completely different. Its major goal is, as its identify suggests, to create the next dynamic vary—that’s, a much bigger hole between the darkish components of a scene and the intense components. In HDR, shiny highlights may be 1,000 nits or extra, relying on the capabilities of your TV. In HDR, a solar shining by way of the forest will actually pop in opposition to the shady foreground, or a campfire will glow like an oasis of heat in opposition to the darkish desert evening. On the suitable TV, this creates an unbelievable picture, however it doesn’t suggest the whole picture is brighter than its SDR counterpart—solely these highlights are. The common brightness of the HDR scene ought to, in principle, be much like that very same scene in SDR (although this could fluctuate from film to film, relying on the way it was graded).
Nevertheless, there’s an issue: Many TVs default to the utmost backlight and distinction ranges in HDR mode, so you possibly can’t crank them any greater for that well-lit lounge like you possibly can with SDR content material. This is not true of all TVs, however it’s common, and it could possibly go away you in fairly a pickle.
Even worse, some TVs truly darken the picture to make up for his or her HDR failings. “The sunshine output of many worth 4K HDR TVs is commonly no completely different than that of many non-HDR TVs,” says Robert Heron, an expert TV calibrator and host of the AVExcel dwelling theater podcast. That is commonest on cheaper TVs, however it could possibly occur with sure midrange and even high-end fashions that minimize corners on brightness. Mix that with HDR’s wider shade palette, which many of those lower-performing TVs cannot reproduce, and the TV has to do one thing to make up for its shortcomings.
When a TV cannot reproduce these shiny highlights on the specified ranges, it performs a course of known as tone-mapping to suit the content material to its capabilities. Say you will have a lower-end TV that is able to solely 350 nits in HDR. When it performs a scene that has a 1,000-nit spotlight, it has to regulate the scene in order that spotlight is simply 350 nits. There are two major methods TV engineers strategy this:
Some TVs will “clip” the intense highlights, preserving the common brightness of the scene the place it’s. The image will not darken a lot, however the highlights could also be a bit blown out.
Different TVs will decrease the common brightness of the scene, preserving the element within the highlights however making the general picture darker than it was initially mastered.
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