Peak brightness is an important aspect to consider when purchasing a monitor. When browsing the web or working, a high SDR peak brightness is important if you're in a brighter environment and are concerned about glare. With HDR content, high peak brightness is important to help small highlights stand out. In this article, we show how we measure peak brightness in SDR and HDR, why it matters, and what to look for so that you can make the best buying decision for your setup and needs.
There are mainly two reasons to get a monitor with a high peak brightness: to combat glare in well-lit environments and produce brighter highlights in HDR. Along with high peak brightness, the brightness must be consistent across different content, especially when image accuracy is required. In HDR, a high brightness makes highlights pop more and helps produce more vibrant colors.
We test peak brightness for both SDR and HDR. We take measurements of a custom real scene peak brightness video and multiple slides, ranging from 2% to 100% coverage of the screen. From those measurements, we also calculate the monitor's ABL, or Automatic Brightness Limiter, which is a measurement of how much the sustained brightness of the screen changes with different window sizes.
We start by warming up the display by displaying a series of video clips for at least 30 minutes. Our SDR measurements are all taken from a PC, using our calibrated settings, but with the brightness at 'Max'. If the monitor supports local dimming in SDR, we set it to our recommended setting based on the results of our 'Local Dimming' test. We take our measurements using a Colorimetry Research CR-100 Colorimeter, using Octave to gather the results for the peak and sustained window tests and CRIapp and Excel for the Real Scene measurements.
For HDR, we connect the display over HDMI, using an HDFury Linker to tell the monitor that the signal we're sending is in HDR. We use the most accurate HDR picture mode without any of our calibration settings applied. Like with our SDR results, we set the local dimming feature to our recommended setting. We use our PC to display each slide and use Octave to record the results. For the HDR Real Scene measurement, we play the video from a Samsung Blu-ray player. We use the same Blu-ray player, with the same settings, for every monitor tested.
We measure the real scene brightness using a custom video clip. We measure the brightness of the lamp at the upper left corner of the screen for 30 seconds using a CR-100 colorimeter. The real scene clip is designed to be more representative of real-world usage than the window tests since most people don't watch test slides all day long. Since this measurement is the closest to the real user experience, it makes up the bulk of our SDR Peak Brightness score. A peak brightness above 300 cd/m² is considered good, and enough to overcome glare in most instances, but you might need higher if the monitor doesn't handle reflections well or if there's direct sunlight shining on the screen.
We perform the SDR peak and sustained brightness tests to see whether there's any brightness variation when displaying different scenes. The peak windows show how bright the monitor can get in the 2%, 10%, 25%, 50%, and 100% windows when the image is only displayed for a short time. The sustained windows show the brightness in the same windows, but for a longer period. Although it isn't as indicative of real-world usage as the real scene measurement, the peak and sustained windows show exactly how bright the display can get and whether there's dimming in any particular window. Generally speaking, a monitor with consistent brightness is best, especially when image accuracy is required, like content creation.
The HDR real scene test is the same as in SDR. We use an HDR version of the same video clip, which gives us a more realistic representation of the monitor's brightness in HDR content. We set the monitor to the appropriate HDR mode with brightness at max and enable local dimming (if applicable). We play the video clip and focus on the lamp in the upper left corner to take the measurement. Most games allow you to adjust the dynamic range of the entire engine, so a real scene peak brightness over 550 cd/m² is considered good enough for gaming in HDR. Movies are a bit different, though, and for a true cinematic HDR experience, a peak real scene brightness of at least 1,000 cd/m² is best. HDR movies can still look good on displays with lower peak brightness, but bright specular highlights don't stand out as much as they should.
We measure the peak and sustained brightness in HDR the same way as in SDR, using the 2%, 10%, 25%, 50%, and 100% slides.
Automatic Brightness Limiter, or ABL, is a feature that changes the brightness according to the content displayed on the screen. It's intended to prevent damaging internal components when displaying large, bright images. The ABL test shows the amount of brightness deviation in the sustained window slides. We calculate the coefficient of variation using the measurements in the sustained windows. Because the human eye is better at noticing luminosity changes in a dark environment than in a bright one, we first linearize the measurements for any noticeable differences in luminosity using the Perceptual Quantizer (PQ) EOTF, making the results more representative of what's perceived. For example, a change of 20 cd/m² is much more noticeable when viewed in the dark than in a bright setting. Most monitors have low or no ABL, so this test accounts for a small percentage of the overall score.
We also test for the lowest possible brightness the monitor can reach in SDR. It's done with a checkerboard pattern, using our recommended settings in SDR. We decrease the brightness setting to its lowest setting and measure the brightness of the screen in the center. This test is important if you plan on using the monitor in a completely dark environment and are sensitive to light. Most monitors should be well below 100cd/m² at their lowest setting, but some people prefer to set their monitors as low as 10-20cd/m².
There's not much that you can do to improve a monitor's peak brightness other than increasing the brightness and choosing the picture mode that gets the brightest, although these picture modes tend to sacrifice image accuracy. Some monitors have an 'Eco mode' intended to reduce power consumption, so you need to ensure that it's disabled if visibility is an issue. 300 cd/m² is usually enough to provide good visibility in most environments, but if there's sunlight or the monitor doesn't handle reflections all that well, then you might want to find one that's closer to 400 cd/m² or brighter. As for HDR, the brighter the better, although there are very few monitors that get bright enough for a true HDR experience. Lastly, when looking at specifications, the advertised brightness can be in 'cd/m²' or in 'nits', which are the same thing.
Except for some budget options, most monitors get bright enough for use in well-lit environments. However, keep in mind that brightness can vary slightly from one unit to another, and the manufacturer's advertised brightness is an estimate that tends to be on the optimistic side. If you're in a room with sunlight or want a better HDR experience, then you should specifically check the monitor's SDR and HDR peak brightness measurements to make sure it satisfies your needs.