Skot (unit)

Key takeaways

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

Reference excerpt

Skot (symbol: sk) is an old and deprecated measurement unit of luminance, used for self-luminous objects (dark luminance). The term comes from Greek skotos, meaning "darkness".

Overview The skot to measure the dark luminance (Dunkelleuchtdichte) was introduced in 1940 by the German Lighting Society (Deutsche Lichttechnische Gesellschaft, LiTG) out of a necessity to describe the luminance of self-luminous objects, which differed so much from that of other objects that it was impractical to describe it using commonly used luminance values. Conversion factors for so called "scotopic stilb" (Skotopisches Stilb) depend on the spectral distribution of the light and were therefore redefined in 1948 by the International Commission on Illumination (Internationale Beleuchtungskommission, IBK) for a specific color temperature of 2042 K or 2046 K, the temperature of solidification of platinum. Before 1948, the definition was based on a temperature of 2360 K as emitted by a wolfram-vacuum lamp. At this temperature, 1 sk = 10−3 asb. The maximum allowed value is 10 skot to avoid the unit being used up into areas of mixed scotopic and photopic vision of the eye.

Unit conversions

See also Nox (unit) to measure the dark illuminance (Dunkelbeleuchtungsstärke) Purkinje effect Photometry (optics) Scotopic lux Scotopic vision

References

Further reading Weaver, Karl S. (1937-01-01) [1936-11-14]. "The Visibility of Radiation at Low Intensities". Journal of the Optical Society of America. 27 (1). Eastman Kodak Company, Rochester, New York, USA: Optical Society of America: 36–43. doi:10.1364/JOSA.27.000036. Retrieved 2023-03-28. Bouma, Pieter Johannes (April 1941) [1941-02-04], "Der Zusammenhang zwischen den Begriffen Leuchtdichte, Helligkeit, Dunkelleuchtdichte usw.", Physica (in German), 8 (4), Natuurkundig Laboratorium der N.V. Philips Gloeilampenfabrieken, Eindhoven, Holland, Netherlands: 413–423, Bibcode:1941Phy.....8..413B, doi:10.1016/S0031-8914(41)90062-9, retrieved 2023-03-28 Bouma, Pieter Johannes (June 1941). "The concept of brightness in connection with blackout problem: The definition of degree in general" (PDF). Philips Technical Review. 6 (6): 161–168 [162]. Archived (PDF) from the original on 2023-01-31. Retrieved 2023-03-29. Dresler, Albert [in German] (1941-12-01). "Dunkelleuchtdichte und Dunkelbeleuchtungsstärke". Archiv für Technisches Messen (in German). Band 2/10 (Lieferung 124). Munich & Berlin, Germany: Verlag R. Oldenbourg: Text T 134. doi:10.1524/teme.1941.121132.jg.224. S2CID 112827871. Verfahren V 420–421. (2 pages) Wulff, ed. (1942-06-03). "G. Analyse. Laboratorium: A. Dresler, Dunkelleuchtdichte und Dunkelbeleuchtungsstärke" (PDF). Chemisches Zentralblatt (Abstract) (in German) (22 (I. Halbjahr)). Berlin, Germany: Maximilian Pflücke, Verlag Chemie G.m.b.H.: 2803. Archived (PDF) from the original on 2023-03-28. Retrieved 2023-03-28. p. 2803: Neuere Anforderungen der Meßtechnik, bes[onders] wie sie hinsichtlich der Bewertung niedriger Leuchtdichten durch den Luftschutz gestellt werden, lassen es als notwendig erscheinen, eine Bewertung von Leuchtdichtehöchstwerten durch eine auf den Zustand des dunkeladaptierten Auges abgestellte Meßtechnik durchzuführen. Es werden im Zusammenhang mit Luftschutzbeleuchtungsproblemen Definitionsgleichungen für die Leuchtdichte u[nd] die Dunkelleuchtdichte gegeben. Das mechan[ische] Lichtäquivalent ist willkürlich festgesetzt als Dunkelleuchtdichte mit der Bezeichnung Skot (abgekürzt Sk), wobei 1 Sk = 10−3 asb ist für den Fall einer Farbtemp[eratur] von 2360° K. Erörterung der Vorzüge und Schwierigkeiten. Die Dunkelbeleuchtungsstärke ist durch die Einheit Nox festgesetzt, wobei 1 Nox zahlenmäßig = 10−3 Lux bei der Farbtemp[eratur] 2360° K beträgt. Normale Selenphotoelemente können mit einer näher angegebenen SCHOTT-Filterkombination für die Messung von Dunkelleuchtdichten u[nd] -beleuchtungsstärken ausreichend angepaßt werden. Für Überschlagsmessungen werden vereinfachte Beziehungen zwischen Nox u[nd] Lux bei gleichen Lampen verschied[ener] Art angegeben. (Arch. techn. Mess. 124. T 134. 2 Seiten [V. 420–1], 2/10. 1941. Berlin.[D] Yamauchi [山内], Jiro [二郎]; Okamatsu [岡松], Masayasu [正泰] (March 1943). "Iro-kō no kashido to anchō 應視 ni okeru sokkō shakudo ni tsuite" 色光の可視度と暗調應視に於ける測光尺度に就いて [On the visibility of colored light and photometric scales in scotopic vision]. 照明學會雑誌 [Lighting Society Magazine] (Electrotechnical examination: Part 6) (in Japanese). 27 (3): 105–112 [108–109]. Archived from the original on 2018-11-03. Retrieved 2023-03-28. (8 pages)

Worked examples

Example 1 — a first encounter with Skot (unit)

Start with the simplest possible case. Write down what Skot (unit) 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 Skot (unit) 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 Skot (unit) 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 Skot (unit)

In research: Skot (unit) 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 Skot (unit) 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: Skot (unit) is common in secondary-school and first-year university syllabi. It links to neighbouring topics Centimetre–gram–second system of units, Photometry, Units of luminance, so understanding it makes those chapters shorter.
In everyday life: Look for Skot (unit) 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.

How to study Skot (unit) in 20 minutes

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

Frequently asked questions

What is Skot (unit) in simple terms?

Skot (symbol: sk) is an old and deprecated measurement unit of luminance, used for self-luminous objects (dark luminance). The term comes from Greek skotos, meaning "darkness".

Why does Skot (unit) 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 Skot (unit)?

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 Skot (unit).