science

Standard-dynamic-range video

Standard-dynamic-range video is a science 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 Standard-dynamic-range video rather than just read about it. In short: Standard-dynamic-range video (SDR video) is a video technology which represents light intensity based on the brightness, contrast and color characteristics and limitations of a cathode ray tube (CRT) display. SDR video is able to represent a video or picture's colors with a maximum luminance around 100 cd/m2, a black level around 0.1 cd/m2 and Rec.709 / sRGB color gamut.

Key takeaways

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

Reference excerpt

Standard-dynamic-range video (SDR video) is a video technology which represents light intensity based on the brightness, contrast and color characteristics and limitations of a cathode ray tube (CRT) display. SDR video is able to represent a video or picture's colors with a maximum luminance around 100 cd/m2, a black level around 0.1 cd/m2 and Rec.709 / sRGB color gamut. It uses the gamma curve as its electro-optical transfer function. The first CRT television sets were manufactured in 1934 and the first color CRT television sets were manufactured in 1954. The term "standard-dynamic-range video" was adopted to distinguish SDR video from high-dynamic-range video (HDR video), a new technology that was developed in the 2010s to overcome SDR's limits.

Technical details

Transfer function Conventional gamma curves:

Opto-electronic transfer function (OETF): Rec. 601 (analog video signals in SD-TV digital video form) Rec. 709 (HD-TV) Rec. 2020 (UHD-TV) sRGB Electro-optical transfer function (EOTF): ITU-R BT.1886 (SDR-TV) sRGB (monitors, printers, World Wide Web) The linear part of the conventional gamma curve was used to limit camera noise in low light video but is no longer needed with high dynamic range (HDR) cameras. An example of a conventional gamma curve would be Rec. 601:

E = { 4.500 L L < 0.018 1.099 L 0.45 − 0.099 L ≥ 0.018 {\displaystyle E={\begin{cases}4.500L&L<0.018\\1.099L^{0.45}-0.099&L\geq 0.018\end{cases}}}

ITU-R Recommendation BT.1886 describe the reference EOTF of SDR. It's a gamma curve representing the response of CRT to video signal. It has been published by ITU in 2011. A transfer function that is closer to Weber's law allows for a larger dynamic range, at the same bit depth, than a conventional gamma curve. HDR standards such as hybrid log–gamma (HLG) and SMPTE ST 2084 allow for a larger dynamic range by using a different transfer function. HLG is compatible with SDR displays.

Color gamut

In some cases the term SDR is also used with a meaning including the standard color gamut (i.e. Rec. 709 / sRGB color primaries). HDR uses wide color gamut (WCG) such as Rec. 2020 or DCI-P3 color primaries.

Dynamic range The dynamic range that can be perceived by the human eye in a single image is around 14 stops. SDR video with a conventional gamma curve and a bit depth of 8-bits per sample has a dynamic range of about 6 stops, assuming a luminance quantisation threshold of 5% is used. A threshold of 5% is used in the paper (instead of the standard 2% threshold) to allow for the typical display being dimmer than ideal. Professional SDR video with a bit depth of 10-bits per sample has a dynamic range of about 10 stops.

Displaying SDR video on modern displays While conventional gamma curves are useful for low light and are compatible with CRT displays, they can only represent a limited dynamic range. Standards require SDR to be viewed on a display with the same characteristics as a CRT (i.e. 100 nits peak brightness, gamma curve, Rec. 709 color primaries). However, current displays are often far more capable than CRT's limits. On such displays, higher brightness and wider color gamut can be displayed by adjusting and trying to enhance the SDR picture. HDR is however required for the creative intents to be preserved.

References

External links ITU-R Recommendation BT.1886

Worked examples

Example 1 — a first encounter with Standard-dynamic-range video

Start with the simplest possible case. Write down what Standard-dynamic-range video claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Standard-dynamic-range video 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 Standard-dynamic-range video 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 Standard-dynamic-range video

In research: Standard-dynamic-range video appears in science 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 Standard-dynamic-range video 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: Standard-dynamic-range video is common in secondary-school and first-year university syllabi. It links to neighbouring topics Color, Display technology, High dynamic range, so understanding it makes those chapters shorter.
In everyday life: Look for Standard-dynamic-range video 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 Standard-dynamic-range video in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Standard-dynamic-range video 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 Standard-dynamic-range video out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Standard-dynamic-range video in simple terms?

Why does Standard-dynamic-range video matter?

Because it connects several science 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 Standard-dynamic-range video?

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 Standard-dynamic-range video.