Nit

Nit (pronounced niht)

(1) The egg of a parasitic insect, especially of a louse, often attached to a hair or a fibre of clothing or the young of such an insect.

(2) In physics, a unit of luminous intensity equal to one candela per square meter (abbreviation: nt).

(3) Slang term to describe those thought unintelligent (truncation of nitwit).

(4) As nitpicker, a description of those who look for minor, unimportant faults or defects (also used in computing as a slang term for debuggers, those who specialise in finding errors in code).

(5) In digital electronics, an increment of data equal to 1.44 binary digits.

Pre 900: From the Middle English nite, from the Old English hnitu, from the Proto-Germanic hnits; cognate with the Dutch neet, the German niss & nisse and the Norwegian nit.  Root was the primitive Indo-European nid, ḱnid & ḱonid; related were the Scottish Gaelic sneadh, the Lithuanian glìnda, the Polish gnida, the Albanian thëri, and the Ancient Greek κονίς (konís).  As used to describe brightness, the use of nit is derived from the Latin nitor (brightness) & nitere (to shine) and was created in the early 1950s as a useful way of defining the luminosity of television displays.

Candlepower

Competition cars used at night need many nits.  The light generated by the array of auxiliary headlamps used to be measured in the hundreds of thousands of candlepower.

Now obsolete, candlepower (cp) was the historic unit of measure for luminous intensity.  It expressed luminosity (level of light intensity) relative to the light emitted by a candle of a specific specification and was first defined in the UK by the Metropolitan Gas Act (1860).  The candle chosen was made of Spermaceti, extracted from the heads of sperm whales.  Under the auspices of the Commission for Illumination (Commission Internationale de l'Eclairage (CIE)), the standard was revised in 1921 to use a carbon filament incandescent lamp and again in 1937 using liquid platinum.

In 1948, the International Standards Organization (ISO) introduced an international standard (SI) named candela (cd) which replaced candlepower, one candlepower being about 0.981 candela; because the values were close, in general use the word candlepower is still often used interchangeably with candela although the latter is the standard in scientific discourse and most industrial applications.  The nit (nt) is a non-SI name also used for this unit (1 nt = 1 cd/m²).  It lacks the transportability of precision needed for scientific use but is ideal for describing the brightness of display devices such as monitors or televisions.  Modern consumer desktop LCD displays had a luminance between 200-350 nits and high-definition LED televisions and display arrays range from 450 to around 1500 nits.