Brightness refers to the maximum luminance of a TV. A higher brightness means the TV can make the picture look brighter, which can help with visibility in a bright room, or make small highlights stand out in HDR. Raising a TV's backlight setting (which is called brightness by some brands) doesn't affect picture quality, so you can easily raise it to the level you prefer.
For these tests, we take measurements of the brightness of a few white rectangles in both SDR and HDR, each covering different sizes on the screen. The measurements are in cd/m2, also known as ‘nits.’ We also measure the EOTF plot for HDR brightness, which tracks how well the TV can display content the way the creator intended. You can also read about peak brightness in monitors here; note that the section is labeled Peak Brightness in monitor reviews, and while it used to be called that in TV reviews, as of Test Bench 1.6 we just call it Brightness.
Brightness matters in any situation in which you want the picture, or part of the picture, to get really bright. Usually, this applies to one of two scenarios:
If your daily use applies to either of those situations, it's important to get a TV that has high brightness. As you can see in the pictures below, these are two TVs with excellent reflection handling, but different brightness. A TV with high brightness results in a more vivid image that's easier to see than one with low brightness.
Our testing for SDR and HDR brightness is fairly straightforward. We use the most accurate picture settings because this is how most people will watch TV, while setting the backlight/brightness setting to max and using the recommended local dimming setting. We use a Konica Minolta LS-100 Luminance Meter to measure the brightness with different content.
We use a video and five test pictures to measure the brightness in both SDR and HDR. The real scene video is supposed to represent content in most shows or movies with bright scenes. Also, the test windows, especially the smaller ones, are meant to test for small highlights.
We use the same videos and pictures for testing the SDR Brightness, HDR Brightness, and HDR Brightness in Game Mode.
The SDR Real Scene Peak Brightness test is most representative of real-world use. Before playing the video, we 'warm up' the TV so that the pixels aren't 'cold' for this test; almost like an athlete stretching their muscles before physical activity, it's important to get the pixels going before the test. We use the luminance meter and focus on the lamp in the upper-left side of the video for 30 seconds to get our final measurement. Anything above 365 cd/m2 should be good enough to combat glare in well-lit rooms. Also, keep in mind that the final luminance measurement can vary up to 20 cd/m2 between measurements.
Our peak window tests measure the maximum brightness of a white rectangle displayed on an area covering a certain percentage of the TV’s screen. This provides an idea of how bright a small highlight – the sun, a distant explosion, etc. – might look on-screen, but the larger areas can also represent very bright areas, like if you're watching something with a bright sky. Also, we use the different sized squares to see how it maintains its brightness across different content.
We use the same setup as the real scene test, and we measure the brightness immediately after the white square appears on-screen. This is because the TV is the brightest at this point.
We measure the SDR sustained window with the same test images as SDR peak window, but the only difference is that we test for brightness after the window has been displayed for a few seconds. This allows the TV to 'stabilize' its brightness and is more representative of content with bright areas that stay on for an extended period, like on a hockey broadcast. Luckily, many TVs don't get much dimmer when a highlight stays on the screen longer.
We measure the HDR Real Scene Peak Brightness with the same test video as in SDR, but it's simply in an HDR format. Unlike in SDR, we don't calibrate the TV for HDR content, so we just use our recommended default picture settings, with local dimming enabled and the backlight at its max. Since HDR content requires the TV to be much brighter, only TVs that get brighter than 650 cd/m2 can really deliver a true HDR experience. The brighter your TV gets, the better, and for most TV manufacturers, their brightest HDR TVs are their premium models.
This test is performed exactly like the SDR peak window test with the same slides. The 2% peak window test is extremely important for HDR, as it tells us how well the TV can make highlights pop. As mentioned before, we expect most TVs to get much brighter in HDR than in SDR, and it's not a good HDR TV if it doesn't.
Once again, we repeat the sustained window test that we did in SDR, but with an HDR video format. Most TVs get a bit dimmer the longer the highlight stays on the screen, but it isn't noticeable.
As part of our Test Bench 1.6 update, we're now measuring the HDR brightness in Game mode. Our testing isn't any different as we use the same video and slides, but we simply put the TV in 'Game' mode. On some TVs, 'Game' mode is simply a setting that allows the lowest input lag, while on others it's a picture mode entirely different from the one we normally use in the regular HDR test. Most TVs don't get significantly dimmer in 'Game' mode, but Samsung models like the Samsung Q80/Q80T QLED do, so the HDR experience isn't the same when gaming.
TVs use algorithms to limit how bright the screen gets, especially with large areas, like in our 100% peak window test. This is done to prevent the entire screen from getting too bright and damaging internal electronics. What this essentially means is small areas get brighter than large areas, and we want to know just how much difference there is between the two. Our Automatic Brightness Limiter (ABL) coefficient variant calculates for the difference in brightness between the sustained windows tests after normalizing for noticeable differences with the Perceptual Quantizer (PQ) EOTF. This means that we only calculate the noticeable differences that we can see when watching TV.
A TV with an ABL of 0 means that the brightness doesn't change across different content. A high ABL is usually found on OLEDs, as large areas are noticeably less bright on those TVs. Also, it's possible for small highlights to be less bright than larger areas because of frame dimming on some TVs, as seen on the Vizio M7 Series Quantum 2020; in this case, the ABL is also high. ABL isn't something you should worry about too much if you just watch SDR content, but it's more important for HDR content.
The Electro-Optical Transfer Function (EOTF) plot is another objective way to measure how well the TV displays HDR content. With HDR content, the creator codes each frame to a certain brightness, so for example, if there's a lamp in a scene that's supposed to be 100 cd/m2, then the TV should display it at 100 cd/m2. However, not all TVs do this perfectly, so some may display scenes at a higher brightness, while other scenes may be lower.
If you look at this EOTF plot, the yellow PQ target represents the target brightness, while the gray line is the measured brightness. If the yellow and gray lines match up perfectly, then the TV displays content exactly how it's supposed to. However, each TV has a max brightness, so eventually, the gray line rolls off at the TV's max brightness. When the gray line is below the target, it doesn't get as bright as intended, and it's brighter when it's above. As you can see in the EOTF plot for the Sony X900H below on the left, it follows the target almost perfectly, but some scenes are still slightly over-brightened.
We also test for the EOTF plot with our 'Make HDR Brighter' settings. These settings are meant for those who want the brightest image possible, even at the cost of image accuracy. Often this includes changing the gamma, contrast, and local dimming settings, but it varies between brands. As you can see on the right, by changing the picture mode and playing around with other settings, we get a brighter HDR image for the X900H.
For the ABL calculation to be significant, it should correspond to the way we perceive different luminosity levels. The eye is much more sensitive to small changes in luminosity in a dark environment than a bright one; so although the measured change in luminosity may be the same, the brighter source is better because we don't notice the change in brightness as much. Essentially, if a screen goes from 25cd/m2 to 20 cd/m2, it's more noticeable than a screen going from 100 cd/m2 to 95 cd/m2. This linearization is done with the PQ EOTF, as you can see below.
PQ is a function that relates luminosity with noticeable differences in brightness. When the PQ curve is divided into 4096 segments (12 bit), there are smaller steps that relate to the change in brightness; the horizontal dotted lines represent each step, and as you can see, the first step in each segment represents a higher change than the last segment. We use this to linearize all of our luminosity measurements for this test, ensuring the ABL best represents what's seen.
You should set your TV’s backlighting/brightness to whatever level looks best in your room. Generally, you should keep it a bit dimmer when watching in a dark room, and make it very bright in a light room. Adjusting the luminance of the TV doesn't affect picture quality, so you can easily put it to whatever setting you like.
Some TVs offer different highlight brightening settings, and often these settings require the enabling of local dimming. This combination can lead to light blooming off bright highlights, like a glowing effect when there are small light sources in a dark scene. This can get distracting, and negatively impacts the picture quality.
For that reason, you should choose the highlight setting that you enjoy the best. This may mean getting the brightest highlights your TV is capable of, or it might mean settling for slightly dimmer highlights that come with less blooming.
Unfortunately, there's no way to control the ABL. Some TVs dim less than others do, though. If you watch content with large areas of bright colors, like hockey or brightly colored cartoons, you should look for a model that doesn’t have too much of a decrease in brightness between the 25% window test and the 100% window test.
At the end of the day, you're the one watching TV, so if you want the make the image brighter, do whatever it takes to make it look better for your viewing experience. These are just generalized recommendation settings, and it changes between TVs.
A TV’s brightness indicates how bright images can get on the screen. It matters most if you watch TV in a well-lit room, as you want your screen to get bright enough to combat glare; otherwise, it may be hard to see. Also, TVs with a high brightness help deliver a better HDR experience, as they allow for highlights to stand out the way the creator intended. We test for TV's brightness to know exactly how bright it can get, but also to see if it remains a consistent brightness level across different content. If you watch TV in dark rooms, then brightness shouldn't be something to worry about.