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Light emitted from lighting equipment such as luminaires and lamps may vary in strength as function of time, either intentionally or unintentionally. Intentional light variations are applied for warning, signalling (e.g. traffic-light signalling , flashing aviation light signals), entertainment (like stage lighting ) with the purpose that ...
Averted vision works because there are virtually no rods (cells which detect dim light in black and white) in the fovea: a small area in the center of the eye. The fovea contains primarily cone cells, which serve as bright light and color detectors and are not as useful during the night. This situation results in a decrease in visual ...
Reverse motion (also known as reverse motion photography or reverse action) is a visual effect in cinematography whereby the action that is filmed is shown backwards (i.e. time-reversed) on screen. It can either be an in-camera effect or an effect produced with the use of an optical printer .
Exposure is a combination of the length of time and the illuminance at the photosensitive material. Exposure time is controlled in a camera by shutter speed, and the illuminance depends on the lens aperture and the scene luminance. Slower shutter speeds (exposing the medium for a longer period of time), greater lens apertures (admitting more ...
Reverse motion – a visual effect in which reversing the order of the frames of a film or video makes time appear to run backward; Reverse tape effects – an audio effect in which reversing the direction of an audio recording renders sounds backward; T-symmetry (or time reversal symmetry) – the expected symmetry of physical laws independent ...
[6] [7] Light can also be captured in motion in a scattering medium using a streak camera that has picosecond temporal resolution, thus removing the need for interferometry and coherent illumination but requires additional hardware to raster scan the two-dimensional (2D) scene, which increases the acquisition time to hours.
This motion is critical to the use of film in a movie camera or movie projector. This is in contrast to a continuous mechanism, whereby the film is constantly in motion and the image is held steady by optical or electronic methods. The reason the intermittent mechanism "works" for the viewer is because of a phenomenon called persistence of vision.
Watts can also be a direct measure of output. In a radiometric sense, an incandescent light bulb is about 80% efficient: 20% of the energy is lost (e.g. by conduction through the lamp base). The remainder is emitted as radiation, mostly in the infrared. Thus, a 60 watt light bulb emits a total radiant flux of about 45 watts.