Editing Film speed (section)

====Warnerke{{anchor|Chapman Jones|Henry Chapman Jones|Jones}}====
<!-- This section is linked from inside or outside this article, preferable by "#Warnerke". Do not rename without keeping in sync. -->
The first known practical [[sensitometry|sensitometer]], which allowed measurements of the speed of photographic materials, was invented by the Polish engineer [[Leon Warnerke]]<ref name="DIN_1934_DIN-4512_Introduction"/>&nbsp;– pseudonym of {{lang|pl|[[Władysław Małachowski]]}} (1837–1900)&nbsp;– in 1880, among the achievements for which he was awarded the [[Progress Medal (RPS)|Progress Medal]] of the [[Photographic Society of Great Britain]]<!-- Today named: Royal Photographic Society (RPS) --> in 1882.<ref name="RPS_2011_Progress_Medal_1882"/><ref name="Jones_1911_Cyclopaedia"/> 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 [[Phosphorescence|phosphorescent]] tablet excited before by the light of a burning [[magnesium]] ribbon.<ref name="Jones_1911_Cyclopaedia"/> The speed of the emulsion was then expressed in 'degrees' Warnerke (sometimes seen as Warn. or °W.) 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° and 25° Warnerke at the time.<!-- According to Josef Maria Eder - History of photography: p. 451: 20° Warnerke = 10° (European) Scheiner, 24-25° Warnerke = 16-18° (European) Scheiner. -->

His system saw some success but proved to be unreliable<ref name="DIN_1934_DIN-4512_Introduction"/> 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.<ref name="Jones_1911_Cyclopaedia"/> The concept, however, was later built upon in 1900 by [[Henry Chapman Jones]] (1855–1932)<!-- 1932-03-07 --> in the development of his<!-- So called Chapman Jones --> plate tester and modified speed system.<ref name="Jones_1911_Cyclopaedia"/><ref name="Hasluck_1905_Jones"/>