science

Mired

Mired 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 Mired rather than just read about it. In short: Contracted from the term micro reciprocal degree, the mired () is a unit of measurement used to express color temperature. Values in mireds are calculated by the formula: M = 1 000 000 K T , {\displaystyle M={\frac {1\,000\,000\,{\text{K}}}{T}},} where T is the colour temperature in units of kelvins and M denotes the resulting mired dimensionless number.

Key takeaways

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

Reference excerpt

Contracted from the term micro reciprocal degree, the mired () is a unit of measurement used to express color temperature. Values in mireds are calculated by the formula:

M = 1 000 000 K T , {\displaystyle M={\frac {1\,000\,000\,{\text{K}}}{T}},}

where T is the colour temperature in units of kelvins and M denotes the resulting mired dimensionless number. The constant 1000000 K is one million kelvins. The SI term for this unit is the reciprocal megakelvin (MK−1), shortened to mirek, but this term has not gained traction. For convenience, decamireds are sometimes used, with a decamired equaling ten mireds. The use of the term mired dates back to Irwin G. Priest's observation in 1932 that the just-noticeable difference between two illuminants is directly related to the difference of the reciprocals of their temperatures, rather than to the difference in their temperatures.

Examples A blue sky, which has a color temperature T of about 25000 K, has a mired value of M = 40 mireds, while a standard electronic photography flash, having a color temperature T of 5000 K, has a mired value of M = 200 mireds.

Applications

Photographic filter and gel

In photography, mireds are used to indicate the color temperature shift provided by a filter or gel for a given film and light source. For instance, to use daylight film (5700 K) to take a photograph under a tungsten light source (3200 K) without introducing a color cast, one would need a corrective filter or gel providing a mired shift

10 6 5700 − 10 6 3200 ≈ − 137 MK − 1 . {\displaystyle {\frac {10^{6}}{5700}}-{\frac {10^{6}}{3200}}\approx -137~{\text{MK}}^{-1}.}

This corresponds to a color temperature blue (CTB) filter. Color gels with negative mired values appear green or blue, while those with positive values appear amber or red.

CCT calculation A number of mathematical methods, including Robertson's, calculate the correlated color temperature of a light source from its chromaticity values. These methods exploit the relatively even spacing of the mired unit internally.

Color description Apple's HomeKit uses the mired unit for specifying color temperature.

References

Illustrations

Worked examples

Example 1 — a first encounter with Mired

Start with the simplest possible case. Write down what Mired 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 Mired 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 Mired 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 Mired

In research: Mired 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 Mired 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: Mired is common in secondary-school and first-year university syllabi. It links to neighbouring topics Color, Non-SI metric units, Units of measurement, so understanding it makes those chapters shorter.
In everyday life: Look for Mired 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 Mired in 20 minutes

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

Frequently asked questions

What is Mired in simple terms?

Contracted from the term micro reciprocal degree, the mired () is a unit of measurement used to express color temperature. Values in mireds are calculated by the formula: M = 1 000 000 K T , {\displaystyle M={\frac {1\,000\,000\,{\text{K}}}{T}},} where T is the colour temperature in units of kelvin…

Why does Mired 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 Mired?

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 Mired.