engineering

High dynamic range

High dynamic range is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand High dynamic range rather than just read about it. In short: High dynamic range (HDR), also known as wide dynamic range, extended dynamic range, or expanded dynamic range, is a signal with a higher dynamic range than usual. The term is often used in discussing the dynamic ranges of images, videos, audio, or radio.

Key takeaways

High dynamic range belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect High dynamic range to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of High dynamic range from memory before moving on to harder problems.

Reference excerpt

High dynamic range (HDR), also known as wide dynamic range, extended dynamic range, or expanded dynamic range, is a signal with a higher dynamic range than usual. The term is often used in discussing the dynamic ranges of images, videos, audio, or radio. It may also apply to the means of recording, processing, and reproducing such signals including analog and digitized signals.

Imaging In this context, the term high dynamic range means there is a large amount of variation in light levels within a scene or an image. The dynamic range refers to the range of luminosity between the brightest area and the darkest area of that scene or image. High-dynamic-range imaging (HDRI) refers to the set of imaging technologies and techniques that allow the dynamic range of images or videos to be increased. It covers the acquisition, creation, storage, distribution and display of images and videos. Modern films have often been shot with cameras featuring a higher dynamic range, and legacy films can be post-converted even if manual intervention will be needed for some frames (as when black-and-white films are converted to color). Also, special effects, especially those that mix real and synthetic footage, require both HDR shooting and rendering. HDR video is also needed in applications that demand high accuracy for capturing temporal aspects of changes in the scene. This is important in monitoring of some industrial processes such as welding, in predictive driver assistance systems in automotive industry, in surveillance video systems, and other applications.

Capture

In photography and videography, a technique, commonly named high dynamic range (HDR) allows the dynamic range of photos and videos to be captured beyond the native capability of the camera. It consists of capturing multiple frames of the same scene but with different exposures and then combining them into one, resulting in an image with a dynamic range higher than the individually captured frames. Some of the sensors on modern phones and cameras may even combine the two images on-chip. This also allows a wider dynamic range being directly available to the user for display or processing without in-pixel compression. Some cameras designed for use in security applications can capture HDR videos by automatically providing two or more images for each frame, with changing exposure. For example, a sensor for 30fps video will give out 60fps with the odd frames at a short exposure time and the even frames at a longer exposure time. Modern CMOS image sensors can often capture high dynamic range images from a single exposure. This reduces the need to use the multi-exposure HDR capture technique. High dynamic range images are used in extreme dynamic range applications like welding or automotive work. In security cameras the term used instead of HDR is "wide dynamic range". Because of the nonlinearity of some sensors image artifacts can be common.

Rendering

High-dynamic-range rendering (HDRR) is the real-time rendering and display of virtual environments using a dynamic range of 65,535:1 or higher (used in computer, gaming, and entertainment technology). HDRR does not require a HDR display and originally used tone mapping to display the rendering on a standard dynamic range display.

Dynamic range compression or expansion

The technologies used to store, transmit, display and print images have limited dynamic range. When captured or created images have a higher dynamic range, they must be tone mapped in order to reduce that dynamic range.

Storage High-dynamic-range formats for image and video files are able to store more dynamic range than traditional 8-bit gamma formats. These formats include:

HDR formats that can be used for both storage and transmission to HDR displays, such as: For video: HDR10 HDR10+ Dolby Vision HLG (backwards compatible with SDR displays) For images: Gain map approaches, which adds a conversion layer on top of SDR data. The result is backwards compatible with SDR displays and storage. ISO 21496-1 Gain Map, evolved from a unification of Apple and Adobe's proposals. Used by Apple under the name Adaptive HDR, ISO 21496-1 supports major file types like JPEG, HEIC, AVIF, JXL, etc. It is supported starting with macOS 15, iOS 18, iPadOS 18, Android 15, and Chromium based browsers. Adobe Gain Map, a gain map image in a JPEG image file; used by Google under the name Ultra HDR and by Samsung under the name Super HDR. Supports gain on 1 or 3 channels. The Ultra HDR and ISO 21496-1 formats are encoded simultaneously in Android 15 for HDR compatibility across Android and iOS devices. Apple Gain Map, which is not fully documented publicly, although documentation is available to decode these images. AVIF is compatible with gain maps, but currently no encoder is available. Apple EDR (Extreme Dynamic Range), used in macOS and iOS. Apple refers to EDR as the combination of hardware and software that allows displaying SDR and HDR content on the same screen. HEIC (HEVC codec in HEIF file format) AVIF (AV1 codec in HEIF file format) JPEG XR JPEG XL HSP, CTA 2072 HDR Still Photo Interface (a format used by Panasonic cameras for photo capture in HDR with the HLG transfer function) Formats that are only used for storage purpose, such as: Raw image formats Formats that use a linear transfer function with high bit-depth Formats that use a logarithmic transfer function OpenEXR was created in 1999 by Industrial Light & Magic (ILM) and released in 2003 as an open source software library. OpenEXR is used for film and television production. RGBE image format, invented by Gregory Ward Larson for the Radiance rendering system and widely used for lighting design and simulation. Academy Color Encoding System (ACES) was created by the Academy of Motion Picture Arts and Sciences and released in December 2014. ACES is a complete color and file management system that works with almost any professional workflow and it supports both HDR and wide color gamut.

Transmission to displays

High dynamic range (HDR) is also the common name of a technology allowing to transmit high dynamic range videos and images to compatible displays. That technology also improves other aspects of transmitted images, such as color gamut. In this context,

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with High dynamic range

Start with the simplest possible case. Write down what High dynamic range claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to High dynamic range before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about High dynamic range ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of High dynamic range

In research: High dynamic range appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses High dynamic range in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: High dynamic range is common in secondary-school and first-year university syllabi. It links to neighbouring topics Display technology, Electrical engineering, High dynamic range, so understanding it makes those chapters shorter.
In everyday life: Look for High dynamic range outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study High dynamic range in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what High dynamic range means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain High dynamic range out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is High dynamic range in simple terms?

Why does High dynamic range matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study High dynamic range?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on High dynamic range.