= Photography
<Photography> records a spatial distribution of <light> as an image. An <optical lens> or <optical pinhole> establishes a correspondence between scene directions and positions on a receiving surface; a <photographic emulsion> or <photodetector> preserves the resulting signal. <Image formation> and recording are separate parts of the process.
This makes <photography> useful for scientific <measurement>: a photograph can preserve the geometry of a <nuclear emulsion> track or the changing appearance of an astronomical source. Interpreting the record still requires calibration. Image brightness depends on the instrument and the duration of illumination as well as on the source, and a visible feature's width can reflect the <point spread function> rather than the object's physical diameter.
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