What dynamic range means
Dynamic range is the span between the darkest and brightest parts of an image that a system can represent. Real scenes have an enormous range: a sunlit window and a shaded corner of the same room differ by a huge factor. Cameras, formats and displays can capture and show only part of that range, so some tones are crushed to black or clipped to white.
Standard dynamic range (SDR) is the traditional approach, built around the limits of older displays. High dynamic range (HDR) extends those limits, allowing brighter highlights, deeper shadows and more detail in between, usually together with a wider color gamut and higher bit depth.
What changes in an HDR picture
The most obvious difference is highlights. In SDR, a bright sky, a reflection or a lamp may all end up at the same top level. In HDR, they can keep separate brightness and texture, and a small bright area can look much brighter than the rest of the picture. Shadows can hold more detail, and colors can stay saturated at higher brightness.
HDR is not simply a brighter picture overall. Well-made HDR keeps most of the image near familiar levels and reserves the extra range for highlights and special details. A common mistake is to assume the point is to make everything glare.
How HDR is carried in the file
Three technical elements usually go together:
- A transfer function. This defines how digital values map to brightness. HDR uses curves such as PQ (perceptual quantizer) or HLG (hybrid log-gamma), rather than the gamma curve of SDR. PQ is based on absolute brightness values, while HLG is designed to be relative and more tolerant of different displays, and it is often associated with broadcast.
- A wider color space. HDR content often uses Rec.2020 as its container, as described in the article on color spaces.
- At least 10-bit video. The wider brightness range stretches gradients, so more levels help avoid banding.
Common HDR formats
- HDR10 is an open, widely supported baseline. It uses PQ with static metadata, meaning one set of brightness information applies to the whole programme.
- HDR10+ adds dynamic metadata that can change scene by scene.
- Dolby Vision also uses dynamic metadata and is a licensed format. Content may carry an HDR10 compatible base layer.
- HLG needs no metadata and can be shown reasonably on both SDR and HDR screens, which suits live broadcast.
Support for each format varies by device and app, and details change over time, so check the current specifications of the equipment you care about.
Displays and what is needed
To benefit from HDR, you need a display that can actually produce more contrast and brightness, along with a player and connection that can pass the signal. Two broad display types handle contrast differently. OLED panels switch individual pixels off, which gives very deep blacks but generally lower peak brightness. LED-backlit LCD panels can reach higher peak brightness, and models with local dimming adjust zones of the backlight, though bright areas can sometimes cause a halo around them.
Many screens advertise HDR support, but this label only means they accept an HDR signal. Peak brightness, contrast, dimming and color coverage vary a lot, and a basic screen may show HDR content without much improvement or even looking dull. Specifications such as nits (a unit of brightness) can help, though the way they are measured differs between manufacturers, so numbers are not always comparable.
Because displays differ, HDR devices perform tone mapping: they adapt the content’s brightness range to what the screen can show. This is why one HDR film can look noticeably different between two TVs.
Why HDR can look wrong
Common causes include a viewing environment that is too bright, picture settings that compress contrast, an HDR signal played on the wrong settings, and conversion from HDR to SDR that is done without a proper mapping. A phone in bright daylight can also behave differently from a dim living room. When HDR video is shown on an SDR screen without correct conversion, colors can look washed out and flat.
Creating and delivering HDR
Shooting HDR often starts with a camera that records at least 10 bits per channel, frequently in a logarithmic profile. The grade is then done on a suitable monitor, and the finished file carries the necessary tags. The wider range makes some tasks more demanding, as described in the notes on color grading. Delivery also takes more care: HDR files generally need a higher video bitrate and a modern codec. The HEVC codec and the AV1 codec are among those that support 10-bit HDR delivery, and platform requirements change, so check the latest guidance before publishing.
A sensible approach for many creators is to produce a good SDR version first. HDR can add value for scenes with strong highlights, such as sunsets, neon lighting and night scenes, but it is not necessary for every project, and a careful SDR delivery will usually reach more viewers reliably.