Editing Light meter (section)

===Extinction types===
[[File:Dremo Light Meter (1931) (15494003563).jpg|thumb|right|upright|Dremo extinction meter<ref>{{cite web |url=http://www.earlyphotography.co.uk/site/entry_E277.html |title=Dremo, 1931 |website=Early Photography |access-date=8 September 2023}}</ref>]]
The next exposure meters, developed at about the same time<ref name=Clerc70/>{{rp|415}} but not displacing actinometers in popularity until the 1920s and 1930s, are known as ''[[Complex index of refraction|extinction]] meters'', evaluating the correct exposure settings by variable attenuation.<ref name=EP-meters>{{cite web |url=http://www.earlyphotography.co.uk/site/meters.html |title=Exposure Meters |website=Early Photography |access-date=8 September 2023}}</ref> One type of extinction meter contained a numbered or lettered row of [[neutral density filter]]s of increasing density. The photographer would position the meter in front of their subject and note the filter with the greatest density that still allowed incident light to pass through. In another example, sold as Heyde's Aktino-Photometer starting from the early 1900s, the photographer views the scene through an eyepiece and turns the meter to vary the effective density until the scene can no longer be seen.<ref>{{cite web |url=http://www.earlyphotography.co.uk/site/entry_E3.html |title=Heyde Aktino-Photometer, 1904 |website=Early Photography |access-date=8 September 2023}}</ref> The letter or number corresponding to the filter strength causing the "extinction" of the scene was used as an index into a chart of appropriate aperture and shutter speed combinations for a given [[film speed]].<ref name=Secret-Exposure>{{cite book |url=https://archive.org/details/secretofexposure00fraprich/page/72/mode/2up |title=The Secret of Exposure |series=Practical Photography |volume=1 |editor=Fraprie, Frank R. |date=1915 |publisher=American Photographic Publishing Company |location=Boston, Massachusetts |quote=In [the Heyde] instrument, blue-glass prisms are used to cut out the light reflected from the object. One looks through the eyepiece and turns the thicker portion of the prisms (one or both, according to the luminosity of the object) into position until the shadow details are suppressed. By reference to Tables, the necessary exposure may readily be found. |access-date=8 September 2023}}</ref>{{rp|72}}

Extinction meters tended to provide inconsistent results because they depended on subjective interpretation and the [[Luminosity function|light sensitivity of the human eye]], which can vary from person to person.<ref>{{cite book |url=https://archive.org/details/exposuremanual0000dunn/ |title=Exposure Manual |chapter-url=https://archive.org/details/exposuremanual0000dunn/page/82/mode/2up |chapter=3: Extinction Meters |author1=Dunn, Jack F. |author2=Wakefield, George L. |edition=Third |date=1974 |publisher=Fountain Press |location=Hertfordshire, England |isbn=0-85242-361-6 |pages=82–86 |url-access=registration |access-date=8 September 2023}}</ref>