light valuen.

Brit.

/ˈlʌɪt valjuː/, U.S.

/ˈlaɪt ˌvælju/

Origin: Formed within English, by compounding. Etymons: light n.¹, value n.

Etymology: < light n.¹ + value n.

1. A measure of the amount of light obtainable from a combustible material expressed as a multiple of cost, weight, etc., relative to some standard reference material, typically spermaceti; (also) the illuminating power of a particular light or lamp as a multiple of that of some standard reference source of light such as a candle (cf. candle n. 1d, candle power n. at candle n. Compounds 2). Now chiefly historical.

ΚΠ

1857 B. H. Paul Man. Techn. Anal. xii. 328 To estimate the light-value, the price of the material must be taken into account, for if the prices of wax and of tallow were = 7:3, the cost of producing the same luminous effect with wax and with tallow would be = 100:39.14.

1875 Gas Jrnl. 14 Dec. 868/1 What is the standard light value as indicated by Somerville's tried automaton instrument?

1887 Trans. Royal Sc. Soc. Arts 11 13 (table) Light value of one cubic foot in grains of sperm.

1905 Proc. Amer. Gas Light Assoc. 22 Appendix p. clxxix Dr. Liebenthal..gives the results of his readings on the Hefner and 1 Candle Power Pentane Lamp, showing the effect of moisture, barometric pressure, and presence of carbonic acid in the air on the light value of these lamps, the curves of which are appended.

1919 Gas Age 1 Mar. 228/1 Its presence in the finished gas is in no way deleterious, except that it is a diluent, resulting in considerable reduction of the light value and a slight reduction of the heating value of the gas.

1966 R. C. Cochrane Meas. Progress iii. 111 One difficulty in establishing a uniform standard of light hinged on the use of the term ‘candlepower’, based by tradition on a natural light source, the light value of an open flame measured by comparison with a sperm oil candle.

2. Photography. A number on an arbitrary scale intended as a guide to exposure times for photographic materials or sensors.

ΘΚΠ

society > leisure > the arts > visual arts > photography > action of taking photograph > technical factors > [noun] > light-value

light value1882

1882 Collier's Cycl. Social & Commerc. Information 735/1 The light value at noon in the month of January is 1.7 but at four o'clock an exposure of five times the duration requisite at that hour would be necessary.

1894 Photogr. Times 16 Nov. 322/1 Various tables are given, but these usually deal with only one factor of the exposure, whereas there are really four: the aperture of the lens or stop, the light-value (differing according to the hour and the month), the condition of the sky, and the rapidity of the plate. The subject itself is another factor.

1970 Which? June 186/2 You then point the meter at the subject and the needle will move along the light value scale... On some meters, instead of transferring the light value from one scale to another, you move a pointer until it overlaps the needle.

2021 D. Young Mastering Nikon D780 (e-book, accessed 5 July 2021) You can use your Spot meter to determine an approximate EV range of light values in the entire image by taking multiple manual spot readings.

Compounds

light-value shutter n. Photography (now disused) a shutter having the aperture and shutter speed settings linked so that they can be altered together in such a way as to keep the amount of light admitted during an exposure constant.

ΚΠ

1954 Sheboygan (Wisconsin) Press 11 Dec. 20/1 (advt.) ‘Ansco’ Super Regent with new ‘Light Value Shutter’.

1958 Newnes Compl. Amateur Photogr. ii. 38 The light-value shutter is a modern device..designed to make speed and aperture setting more easy, and making use of the light value system.

This entry has been updated (OED Third Edition, December 2021).

单词	light value
释义	light valuen. Brit. /ˈlʌɪt valjuː/, U.S. /ˈlaɪt ˌvælju/ Origin: Formed within English, by compounding. Etymons: light n.¹, value n. Etymology: < light n.¹ + value n. 1. A measure of the amount of light obtainable from a combustible material expressed as a multiple of cost, weight, etc., relative to some standard reference material, typically spermaceti; (also) the illuminating power of a particular light or lamp as a multiple of that of some standard reference source of light such as a candle (cf. candle n. 1d, candle power n. at candle n. Compounds 2). Now chiefly historical. ΚΠ 1857 B. H. Paul Man. Techn. Anal. xii. 328 To estimate the light-value, the price of the material must be taken into account, for if the prices of wax and of tallow were = 7:3, the cost of producing the same luminous effect with wax and with tallow would be = 100:39.14. 1875 Gas Jrnl. 14 Dec. 868/1 What is the standard light value as indicated by Somerville's tried automaton instrument? 1887 Trans. Royal Sc. Soc. Arts 11 13 (table) Light value of one cubic foot in grains of sperm. 1905 Proc. Amer. Gas Light Assoc. 22 Appendix p. clxxix Dr. Liebenthal..gives the results of his readings on the Hefner and 1 Candle Power Pentane Lamp, showing the effect of moisture, barometric pressure, and presence of carbonic acid in the air on the light value of these lamps, the curves of which are appended. 1919 Gas Age 1 Mar. 228/1 Its presence in the finished gas is in no way deleterious, except that it is a diluent, resulting in considerable reduction of the light value and a slight reduction of the heating value of the gas. 1966 R. C. Cochrane Meas. Progress iii. 111 One difficulty in establishing a uniform standard of light hinged on the use of the term ‘candlepower’, based by tradition on a natural light source, the light value of an open flame measured by comparison with a sperm oil candle. 2. Photography. A number on an arbitrary scale intended as a guide to exposure times for photographic materials or sensors. ΘΚΠ society > leisure > the arts > visual arts > photography > action of taking photograph > technical factors > [noun] > light-value light value1882 1882 Collier's Cycl. Social & Commerc. Information 735/1 The light value at noon in the month of January is 1.7 but at four o'clock an exposure of five times the duration requisite at that hour would be necessary. 1894 Photogr. Times 16 Nov. 322/1 Various tables are given, but these usually deal with only one factor of the exposure, whereas there are really four: the aperture of the lens or stop, the light-value (differing according to the hour and the month), the condition of the sky, and the rapidity of the plate. The subject itself is another factor. 1970 Which? June 186/2 You then point the meter at the subject and the needle will move along the light value scale... On some meters, instead of transferring the light value from one scale to another, you move a pointer until it overlaps the needle. 2021 D. Young Mastering Nikon D780 (e-book, accessed 5 July 2021) You can use your Spot meter to determine an approximate EV range of light values in the entire image by taking multiple manual spot readings. Compounds light-value shutter n. Photography (now disused) a shutter having the aperture and shutter speed settings linked so that they can be altered together in such a way as to keep the amount of light admitted during an exposure constant. ΚΠ 1954 Sheboygan (Wisconsin) Press 11 Dec. 20/1 (advt.) ‘Ansco’ Super Regent with new ‘Light Value Shutter’. 1958 Newnes Compl. Amateur Photogr. ii. 38 The light-value shutter is a modern device..designed to make speed and aperture setting more easy, and making use of the light value system. This entry has been updated (OED Third Edition, December 2021). < n.1857
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