[{"@context":"http:\/\/schema.org\/","@type":"BlogPosting","@id":"https:\/\/wiki.edu.vn\/en\/wiki43\/film-speed-wikipedia-100\/#BlogPosting","mainEntityOfPage":"https:\/\/wiki.edu.vn\/en\/wiki43\/film-speed-wikipedia-100\/","headline":"Film speed – Wikipedia","name":"Film speed – Wikipedia","description":"before-content-x4 Measure of a photographic film’s sensitivity to light “Slow film” redirects here. For the genre of films, see slow","datePublished":"2020-12-15","dateModified":"2020-12-15","author":{"@type":"Person","@id":"https:\/\/wiki.edu.vn\/en\/wiki43\/author\/lordneo\/#Person","name":"lordneo","url":"https:\/\/wiki.edu.vn\/en\/wiki43\/author\/lordneo\/","image":{"@type":"ImageObject","@id":"https:\/\/secure.gravatar.com\/avatar\/c9645c498c9701c88b89b8537773dd7c?s=96&d=mm&r=g","url":"https:\/\/secure.gravatar.com\/avatar\/c9645c498c9701c88b89b8537773dd7c?s=96&d=mm&r=g","height":96,"width":96}},"publisher":{"@type":"Organization","name":"Enzyklop\u00e4die","logo":{"@type":"ImageObject","@id":"https:\/\/wiki.edu.vn\/wiki4\/wp-content\/uploads\/2023\/08\/download.jpg","url":"https:\/\/wiki.edu.vn\/wiki4\/wp-content\/uploads\/2023\/08\/download.jpg","width":600,"height":60}},"image":{"@type":"ImageObject","@id":"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/thumb\/d\/dc\/Provia_100F_RDPIII_Box_with_ISO_film_speed.jpg\/220px-Provia_100F_RDPIII_Box_with_ISO_film_speed.jpg","url":"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/thumb\/d\/dc\/Provia_100F_RDPIII_Box_with_ISO_film_speed.jpg\/220px-Provia_100F_RDPIII_Box_with_ISO_film_speed.jpg","height":"189","width":"220"},"url":"https:\/\/wiki.edu.vn\/en\/wiki43\/film-speed-wikipedia-100\/","wordCount":30142,"articleBody":"     (adsbygoogle = window.adsbygoogle || []).push({});before-content-x4Measure of a photographic film’s sensitivity to light“Slow film” redirects here. For the genre of films, see slow cinema.       (adsbygoogle = window.adsbygoogle || []).push({});after-content-x4Film speed is the measure of a photographic film’s sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system. A closely related ISO system is used to describe the relationship between exposure and output image lightness in digital cameras.Relatively insensitive film, with a correspondingly lower speed index, requires more exposure to light to produce the same image density as a more sensitive film, and is thus commonly termed a slow film. Highly sensitive films are correspondingly termed fast films. In both digital and film photography, the reduction of exposure corresponding to use of higher sensitivities generally leads to reduced image quality (via coarser film grain or higher image noise of other types). In short, the higher the sensitivity, the grainier the image will be. Ultimately sensitivity is limited by the quantum efficiency of the film or sensor.         (adsbygoogle = window.adsbygoogle || []).push({});after-content-x4This film container denotes its speed as ISO 100\/21\u00b0, including both arithmetic (100 ASA) and logarithmic (21 DIN) components. The second is often dropped, making (e.g.) “ISO 100” effectively equivalent to the older ASA speed. (As is common, the “100” in the film name alludes to its ISO rating.)Table of ContentsFilm speed measurement systems[edit]Historical systems[edit]Warnerke[edit]Hurter & Driffield[edit]Scheiner[edit]DIN[edit]BSI[edit]Weston[edit]General Electric[edit]ASA[edit]GOST[edit]Current system: ISO[edit]Conversion between current scales[edit]Historic ASA and DIN conversion[edit]Determining film speed[edit]Applying film speed[edit]Exposure index[edit]Reciprocity[edit]Film sensitivity and grain[edit]Marketing anomalies[edit]Digital camera ISO speed and exposure index[edit]The ISO (International Organization of Standards) 12232:2019 standard[edit]Measurements and calculations[edit]Saturation-based speed[edit]Noise-based speed[edit]Standard output sensitivity (SOS)[edit]Discussion[edit]See also[edit]References[edit]Further reading[edit]External links[edit]Film speed measurement systems[edit]Historical systems[edit]Warnerke[edit]The first known practical sensitometer, which allowed measurements of the speed of photographic materials, was invented by the Polish engineer Leon Warnerke[1] \u2013 pseudonym of W\u0142adys\u0142aw Ma\u0142achowski (1837\u20131900) \u2013 in 1880, among the achievements for which he was awarded the Progress Medal of the Photographic Society of Great Britain in 1882.[2][3] It was commercialized since 1881.The Warnerke Standard Sensitometer consisted of a frame holding an opaque screen with an array of typically 25 numbered, gradually pigmented squares brought into contact with the photographic plate during a timed test exposure under a phosphorescent tablet excited before by the light of a burning magnesium ribbon.[3] The speed of the emulsion was then expressed in ‘degrees’ Warnerke (sometimes seen as Warn. or \u00b0W.) corresponding with the last number visible on the exposed plate after development and fixation. Each number represented an increase of 1\/3 in speed, typical plate speeds were between 10\u00b0 and 25\u00b0 Warnerke at the time.       (adsbygoogle = window.adsbygoogle || []).push({});after-content-x4His system saw some success but proved to be unreliable[1] due to its spectral sensitivity to light, the fading intensity of the light emitted by the phosphorescent tablet after its excitation as well as high built-tolerances.[3] The concept, however, was later built upon in 1900 by Henry Chapman Jones (1855\u20131932) in the development of his plate tester and modified speed system.[3][4]Hurter & Driffield[edit]Another early practical system for measuring the sensitivity of an emulsion was that of Hurter and Driffield (H&D), originally described in 1890, by the Swiss-born Ferdinand Hurter (1844\u20131898) and British Vero Charles Driffield (1848\u20131915). In their system, speed numbers were inversely proportional to the exposure required. For example, an emulsion rated at 250 H&D would require ten times the exposure of an emulsion rated at 2500 H&D.[5]The methods to determine the sensitivity were later modified in 1925 (in regard to the light source used) and in 1928 (regarding light source, developer and proportional factor)\u2014this later variant was sometimes called “H&D 10”. The H&D system was officially[6] accepted as a standard in the former Soviet Union from 1928 until September 1951, when it was superseded by GOST 2817\u201350.Scheiner[edit]The Scheinergrade (Sch.) system was devised by the German astronomer Julius Scheiner (1858\u20131913) in 1894 originally as a method of comparing the speeds of plates used for astronomical photography. Scheiner’s system rated the speed of a plate by the least exposure to produce a visible darkening upon development. Speed was expressed in degrees Scheiner, originally ranging from 1\u00b0 Sch. to 20\u00b0 Sch., where an increment of 19\u00b0 Sch. corresponded to a hundredfold increase in sensitivity, which meant that an increment of 3\u00b0 Sch. came close to a doubling of sensitivity.[5][7]100193=2.06914…\u22482{displaystyle {sqrt[{19}]{100}}^{3}=2.06914…approx 2}The system was later extended to cover larger ranges and some of its practical shortcomings were addressed by the Austrian scientist Josef Maria Eder (1855\u20131944)[1] and Flemish-born botanist Walter Hecht\u00a0[de] (1896\u20131960), (who, in 1919\/1920, jointly developed their Eder\u2013Hecht neutral wedge sensitometer measuring emulsion speeds in Eder\u2013Hecht grades). Still, it remained difficult for manufacturers to reliably determine film speeds, often only by comparing with competing products,[1] so that an increasing number of modified semi-Scheiner-based systems started to spread, which no longer followed Scheiner’s original procedures and thereby defeated the idea of comparability.[1][8]Scheiner’s system was eventually abandoned in Germany, when the standardized DIN system was introduced in 1934. In various forms, it continued to be in widespread use in other countries for some time.DIN[edit]The DIN system, officially DIN standard 4512 by the Deutsches Institut f\u00fcr Normung (then known as the Deutscher Normenausschu\u00df (DNA)), was published in January 1934. It grew out of drafts for a standardized method of sensitometry put forward by the Deutscher Normenausschu\u00df f\u00fcr Phototechnik[8] as proposed by the committee for sensitometry of the Deutsche Gesellschaft f\u00fcr photographische Forschung[9] since 1930[10][11] and presented by Robert Luther\u00a0[de][11][12] (1868\u20131945) and Emanuel Goldberg[12] (1881\u20131970) at the influential VIII. International Congress of Photography (German: Internationaler Kongre\u00df f\u00fcr wissenschaftliche und angewandte Photographie) held in Dresden from 3 to 8 August 1931.[8][13]The DIN system was inspired by Scheiner’s system,[1] but the sensitivities were represented as the base 10 logarithm of the sensitivity multiplied by 10, similar to decibels. Thus an increase of 20\u00b0 (and not 19\u00b0 as in Scheiner’s system) represented a hundredfold increase in sensitivity, and a difference of 3\u00b0 was much closer to the base 10 logarithm of 2 (0.30103…):[7]log10\u2061(2)=0.30103…\u22483\/10{displaystyle log _{10}{(2)}=0.30103…approx 3\/10}  A box of Agfacolor Neu with the instruction “expose as 15\/10\u00b0 DIN” (in German).As in the Scheiner system, speeds were expressed in ‘degrees’. Originally the sensitivity was written as a fraction with ‘tenths’ (for example “18\/10\u00b0 DIN”),[14] where the resultant value 1.8 represented the relative base 10 logarithm of the speed. ‘Tenths’ were later abandoned with DIN 4512:1957-11, and the example above would be written as “18\u00b0 DIN”.[5] The degree symbol was finally dropped with DIN 4512:1961-10. This revision also saw significant changes in the definition of film speeds in order to accommodate then-recent changes in the American ASA PH2.5-1960 standard, so that film speeds of black-and-white negative film effectively would become doubled, that is, a film previously marked as “18\u00b0 DIN” would now be labeled as “21 DIN” without emulsion changes.Originally only meant for black-and-white negative film, the system was later extended and regrouped into nine parts, including DIN 4512-1:1971-04 for black-and-white negative film, DIN 4512-4:1977-06 for color reversal film and DIN 4512-5:1977-10 for color negative film.On an international level the German DIN 4512 system has been effectively superseded in the 1980s by ISO 6:1974,[15] ISO 2240:1982,[16] and ISO 5800:1979[17] where the same sensitivity is written in linear and logarithmic form as “ISO 100\/21\u00b0” (now again with degree symbol). These ISO standards were subsequently adopted by DIN as well. Finally, the latest DIN 4512 revisions were replaced by corresponding ISO standards, DIN 4512-1:1993-05 by DIN ISO 6:1996-02 in September 2000, DIN 4512-4:1985-08 by DIN ISO 2240:1998-06 and DIN 4512-5:1990-11 by DIN ISO 5800:1998-06 both in July 2002.BSI[edit]This section needs expansion with: details on the different BS and BSI standard variants, their development over time, their applications, and their relation to other standards such as DIN, ASA etc.. You can help by adding to it.  (August 2013)The film speed scale recommended by the British Standards Institution (BSI) was almost identical to the DIN system except that the BS number was 10 degrees greater than the DIN number.[citation needed]Weston[edit]  Weston Model 650 light meter from about 1935  Early Weston Master light meter 1935-1945Before the advent of the ASA system, the system of Weston film speed ratings was introduced by Edward Faraday Weston (1878\u20131971) and his father Dr. Edward Weston (1850\u20131936), a British-born electrical engineer, industrialist and founder of the US-based Weston Electrical Instrument Corporation,[18] with the Weston model 617, one of the earliest photo-electric exposure meters, in August 1932. The meter and film rating system were invented by William Nelson Goodwin, Jr.,[19][20] who worked for them[21] and later received a Howard N. Potts Medal for his contributions to engineering.The company tested and frequently published speed ratings for most films of the time. Weston film speed ratings could since be found on most Weston exposure meters and were sometimes referred to by film manufacturers and third parties[22] in their exposure guidelines. Since manufacturers were sometimes creative about film speeds, the company went as far as to warn users about unauthorized uses of their film ratings in their “Weston film ratings” booklets.[23]The Weston Cadet (model 852 introduced in 1949), Direct Reading (model 853 introduced 1954) and Master III (models 737 and S141.3 introduced in 1956) were the first in their line of exposure meters to switch and utilize the meanwhile established ASA scale instead. Other models used the original Weston scale up until ca. 1955. The company continued to publish Weston film ratings after 1955,[24] but while their recommended values often differed slightly from the ASA film speeds found on film boxes, these newer Weston values were based on the ASA system and had to be converted for use with older Weston meters by subtracting 1\/3 exposure stop as per Weston’s recommendation.[24] Vice versa, “old” Weston film speed ratings could be converted into “new” Westons and the ASA scale by adding the same amount, that is, a film rating of 100 Weston (up to 1955) corresponded with 125 ASA (as per ASA PH2.5-1954 and before). This conversion was not necessary on Weston meters manufactured and Weston film ratings published since 1956 due to their inherent use of the ASA system; however the changes of the ASA PH2.5-1960 revision may be taken into account when comparing with newer ASA or ISO values.General Electric[edit]Prior to the establishment of the ASA scale[25] and similar to Weston film speed ratings another manufacturer of photo-electric exposure meters, General Electric, developed its own rating system of so-called General Electric film values (often abbreviated as G-E or GE) around 1937.Film speed values for use with their meters were published in regularly updated General Electric Film Values[26] leaflets and in the General Electric Photo Data Book.[27]General Electric switched to use the ASA scale in 1946. Meters manufactured since February 1946 are equipped with the ASA scale (labeled “Exposure Index”) already. For some of the older meters with scales in “Film Speed” or “Film Value” (e.g. models DW-48, DW-49 as well as early DW-58 and GW-68 variants), replaceable hoods with ASA scales were available from the manufacturer.[26][28] The company continued to publish recommended film values after that date, however, they were then aligned to the ASA scale.ASA[edit]Based on earlier research work by Loyd Ancile Jones (1884\u20131954) of Kodak and inspired by the systems of Weston film speed ratings[24] and General Electric film values,[26] the American Standards Association (now named ANSI) defined a new method to determine and specify film speeds of black-and-white negative films in 1943. ASA Z38.2.1\u20131943 was revised in 1946 and 1947 before the standard grew into ASA PH2.5-1954. Originally, ASA values were frequently referred to as American standard speed numbers or ASA exposure-index numbers. (See also: Exposure Index (EI).)The ASA scale is a linear scale, that is, a film denoted as having a film speed of 200 ASA is twice as fast as a film with 100 ASA.The ASA standard underwent a major revision in 1960 with ASA PH2.5-1960, when the method to determine film speed was refined and previously applied safety factors against under-exposure were abandoned, effectively doubling the nominal speed of many black-and-white negative films. For example, an Ilford HP3 that had been rated at 200 ASA before 1960 was labeled 400 ASA afterwards without any change to the emulsion. Similar changes were applied to the DIN system with DIN 4512:1961-10 and the BS system with BS 1380:1963 in the following years.In addition to the established arithmetic speed scale, ASA PH2.5-1960 also introduced logarithmic ASA grades (100 ASA = 5\u00b0 ASA), where a difference of 1\u00b0 ASA represented a full exposure stop and therefore the doubling of a film speed. For some while, ASA grades were also printed on film boxes, and they saw life in the form of the APEX speed value Sv (without degree symbol) as well.ASA PH2.5-1960 was revised as ANSI PH2.5-1979, without the logarithmic speeds, and later replaced by NAPM IT2.5\u20131986 of the National Association of Photographic Manufacturers, which represented the US adoption of the international standard ISO\u00a06. The latest issue of ANSI\/NAPM IT2.5 was published in 1993.The standard for color negative film was introduced as ASA PH2.27-1965 and saw a string of revisions in 1971, 1976, 1979 and 1981, before it finally became ANSI IT2.27\u20131988 prior to its withdrawal.Color reversal film speeds were defined in ANSI PH2.21-1983, which was revised in 1989 before it became ANSI\/NAPM IT2.21 in 1994, the US adoption of the ISO\u00a02240 standard.On an international level, the ASA system was superseded by the ISO film speed system between 1982 and 1987, however, the arithmetic ASA speed scale continued to live on as the linear speed value of the ISO system.GOST[edit]  A box of Svema film, with a sensitivity of 65 \u0413\u041e\u0421\u0422GOST (Cyrillic: \u0413\u041e\u0421\u0422) was an arithmetic film speed scale defined in GOST 2817-45 and GOST 2817\u201350.[29][30] It was used in the former Soviet Union since October 1951,[citation needed] replacing Hurter & Driffield (H&D, Cyrillic: \u0425\u0438\u0414) numbers,[29] which had been used since 1928.[citation needed]GOST 2817-50 was similar to the ASA standard, having been based on a speed point at a density 0.2 above base plus fog, as opposed to the ASA’s 0.1.[31] GOST markings are only found on pre-1987 photographic equipment (film, cameras, lightmeters, etc.) of Soviet Union manufacture.[32]On 1 January 1987, the GOST scale was realigned to the ISO scale with GOST 10691\u201384,[33]This evolved into multiple parts including GOST 10691.6\u201388[34] and GOST 10691.5\u201388,[35] which both became functional on 1 January 1991.Current system: ISO[edit]The ASA and DIN film speed standards have been combined into the ISO standards since 1974.The current International Standard for measuring the speed of colour negative film is ISO 5800:2001[17] (first published in 1979, revised in November 1987) from the International Organization for Standardization (ISO). Related standards ISO 6:1993[15] (first published in 1974) and ISO 2240:2003[16] (first published in July 1982, revised in September 1994 and corrected in October 2003) define scales for speeds of black-and-white negative film and colour reversal film, respectively.The determination of ISO speeds with digital still-cameras is described in ISO 12232:2019 (first published in August 1998, revised in April 2006, corrected in October 2006 and again revised in February 2019).[36][37]The ISO system defines both an arithmetic and a logarithmic scale.[38] The arithmetic ISO scale corresponds to the arithmetic ASA system, where a doubling of film sensitivity is represented by a doubling of the numerical film speed value. In the logarithmic ISO scale, which corresponds to the DIN scale, adding 3\u00b0 to the numerical value constitutes a doubling of sensitivity. For example, a film rated ISO\u00a0200\/24\u00b0 is twice as sensitive as one rated ISO\u00a0100\/21\u00b0.[38]Commonly, the logarithmic speed is omitted; for example, “ISO 100” denotes “ISO 100\/21\u00b0”,[39] while logarithmic ISO speeds are written as “ISO 21\u00b0” as per the standard.Conversion between current scales[edit]  A Yashica FR with both ASA and DIN markingsConversion from arithmetic speed S to logarithmic speed S\u00b0 is given by[15]S\u2218=10log\u2061S+1{displaystyle S^{circ }=10log S+1}and rounding to the nearest integer; the log is base 10. Conversion from logarithmic speed to arithmetic speed is given by[40]S=10(S\u2218\u22121)\/10{displaystyle S=10^{left({S^{circ }-1}right)\/10}}and rounding to the nearest standard arithmetic speed in Table\u00a01 below."},{"@context":"http:\/\/schema.org\/","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"https:\/\/wiki.edu.vn\/en\/wiki43\/#breadcrumbitem","name":"Enzyklop\u00e4die"}},{"@type":"ListItem","position":2,"item":{"@id":"https:\/\/wiki.edu.vn\/en\/wiki43\/film-speed-wikipedia-100\/#breadcrumbitem","name":"Film speed – Wikipedia"}}]}]