optics, radiometry is the field that studies the measurementof electromagnetic radiation, including visible light. Note that light is also measured using the techniques of photometry, which deal with brightness as perceived by the human eye, rather than absolute power.
Radiometry is important in
astronomy, especially radio astronomy, and is important for Earth remote sensing. The measurement techniques categorized as "radiometry" in optics are called "photometry" in some astronomical applications, contrary to the optics usage of the term.
Spectroradiometry is the measurement of absolute radiometric quantities in narrow bands of wavelength. [cite book|title=Focal Encyclopedia of Photography|publisher=
Focal Press| author=Leslie D. Stroebel and Richard D. Zakia | year=1993 | edition=3rd ed.|page=p. 115 |isbn=0240514173 | url = http://books.google.com/books?id=CU7-2ZLGFpYC&pg=PA115&dq=spectroradiometry+intitle:%22Focal+Encyclopedia+of+Photography%22&lr=&as_brr=0&ei=o3aVR8nSMoSkiQGhl_SiBw&sig=rPCx5nkENgpC-gV4orKVH6lYUoU#PPA115,M1 ]
* [http://www.optics.arizona.edu/Palmer/rpfaq/rpfaq.htm Radiometry and photometry FAQ] Professor Jim Palmer's Radiometry FAQ page (University of Arizona).
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