Editing Light meter (section)

===Reflected and incident measurements===
Exposure meters generally are sorted into reflected-light or incident-light types, depending on the method used to measure the scene.

'''Reflected-light meters''' measure the light ''reflected by the scene'' to be photographed.<ref name=Dunn-Wakefield-ch4/> All in-camera meters are reflected-light meters. Reflected-light meters are calibrated to show the appropriate exposure for "average" scenes.<ref name=Focal78/>{{rp|74}} An unusual scene with a preponderance of light colors or specular highlights would have a higher reflectance; a reflected-light meter taking a reading would incorrectly compensate for the difference in [[reflectance]] and lead to underexposure.  Badly underexposed sunset photos are common exactly because of this effect: the brightness of the setting sun fools the camera's light meter and, unless the in-camera logic or the photographer take care to compensate, the picture will be grossly underexposed and dull.

[[File:Sekonic L 398.jpg|thumb|left|upright|Sekonic L-398, with opalescent incident light-integrating dome]]
This pitfall (but not in the setting-sun case) is avoided by '''incident-light meters''' which measure the amount of light ''falling on the subject'' using a diffuser with a flat or (more commonly) hemispherical field of view placed on top of the light sensor.<ref name=Dunn-Wakefield-ch5>{{cite book |url=https://archive.org/details/exposuremanual0000dunn/ |title=Exposure Manual |chapter-url=https://archive.org/details/exposuremanual0000dunn/page/122/mode/2up |chapter=5: Photoelectric Incident-light Meters and Attachments |author1=Dunn, Jack F. |author2=Wakefield, George L. |edition=Third |date=1974 |publisher=Fountain Press |location=Hertfordshire, England |isbn=0-85242-361-6 |pages=122–140 |url-access=registration |access-date=8 September 2023}}</ref> Because the incident-light reading is independent of the subject's reflectance, it is less likely to lead to incorrect exposures for subjects with unusual average reflectance. Taking an incident-light reading requires placing the meter at the subject's position and pointing it in the general direction of the camera, something not always achievable in practice, e.g., in [[landscape photography]] where the subject distance approaches infinity.

[[File:Asahi Pentax Digital Spotmeter, against color chart (Pcs34560).jpg|thumb|right|upright|Pentax Digital Spotmeter]]
Another way to avoid under- or over-exposure for subjects with unusual reflectance is to use a '''spot meter''': a specialized reflected-light meter that measures light in a very tight [[Elliptical cone|cone]], typically with a one degree circular [[Angle of view#Calculating a camera's angle of view|angle of view]].<ref name=Dunn-Wakefield-ch6>{{cite book |url=https://archive.org/details/exposuremanual0000dunn/ |title=Exposure Manual |chapter-url=https://archive.org/details/exposuremanual0000dunn/page/140/mode/2up |chapter=6: Exposure Photometers |author1=Dunn, Jack F. |author2=Wakefield, George L. |edition=Third |date=1974 |publisher=Fountain Press |location=Hertfordshire, England |isbn=0-85242-361-6 |pages=141–177 |url-access=registration |access-date=8 September 2023}}</ref> An experienced photographer can take multiple readings over the shadows, midrange, and highlights of the scene to determine optimal exposure, using systems like the [[Zone System]].<ref name=Hicks99/>{{rp|102;126}}

Many modern cameras include sophisticated [[Metering mode#Multi-zone metering|multi-segment metering]] systems that measure the [[luminance]] of different parts of the scene to determine the optimal exposure.<ref name=Hicks99/>{{rp|102}} When using a film whose spectral sensitivity is not a good match to that of the light meter, for example [[orthochromatic]] [[Black and White Photography|black-and-white]] or infrared film, the meter may require special filters and re-calibration to match the sensitivity of the film.<ref name=Hicks99/>{{rp|89–92}}

[[File:Gossen-variosix hg.jpg|thumb|left|upright|Gossen Variosix (Luna-Star) F, capable of reflected, incident, and flash measurements]]
There are other types of specialized photographic light meters. Flash meters are used in flash photography to verify correct exposure. Color meters are used where high fidelity in color reproduction is required. [[Densitometer]]s are used in photographic reproduction.