Basic Stage Lighting Ch 17 Vocab

ref. to optical features of a stage lighting instrument-- the reflector and lenses

light reflection off a shiny surface.
angle of incidence=angle of reflection

in theatrical SPOTLIGHT, a glass reflector with dichroic coating which allows some wavelengths of light to pass through while reflecting others

specific point at which a light source must be placed in relationship to the reflector in order to achieve desired reflective pattern ie when light was most focused, not blurry, during demo

reflector cast in shape of part of a sphere, returns light back to its focal point which is located in the exact center-- found in fresnel spotlights.

reflector cast in shape of part of a parabola; reflects light in parallel rays-- found in PAR fixtures

reflector cast in shape of part of an ellipsoid; reflects light back to its secondary focal point-- found in ellipsoidal reflector spotlights

point nearest the reflector; if light source is positioned here, rays striking reflector are redirected to converge at conjugate focal point

the more distant focal point

the bending of light rays as they pass through mediums with different densities

when a ray of light passes into a denser medium (ie air 2 glass) it is bent toward a perpendicular drawn to the surface at the point of entry. when it reemerges into the less dense medium, it is bent away from a perp. drawn at that point

a lens with one flat [plano] side and one outwardly curved convex side-- found in ellipsoidal reflector spotlights

pt. at which parallel rays of light converge after passing through a lens-- if source of light is placed at the focal point, parallel rays will result. moving source of light away from focal point causes rays to diverge or converge

the distance from the focal point to the center of the lens; measured in in. or mm.

uses ellipsoidal reflector; creates concentrated sharp light and has built-in beam shaping capability (shutters, iris, gobos)

clamp used to attach a lighting instrument to a pipe

the U-shaped part that holds the C-clamp and allows instrument to tilt

in ERS, position at which shutters, iris, and gobos are located; close to reflector's secondary focal point where light rays cross

metal moveable plates, inserted at gate of ERS, that allows beam to be shaped in linear manner from any of four directions

device, located at gate of ERS, makes the beam's circumference larger or smaller

ERS with moveable lenses that provide adjustable beam diameter

allows adjustment in beam edge but not spread; older ellipsoidals use two plano-convex lenses belly to belly in a barrel

usu. provides 3 dif. beam spreads; allows for movement of lenses in relationship to one another or substitution of one lens for another

provides variable beam spread within fixed range;rear plano convex, front bi convex lens slide toward or away from each other

in spotlight beam, where light drops off to 50% of maximum intensity

in spotlight beam, where light drops off to 10% of max intensity

named after inventor of the lens; has spherical reflector and ability to change beam size

when lamp is moved all the way forward, light beam achieves its largest diameter

when lamp is moved all the way back away from the lens, light beam becomes narrowest

accessory for fresnel that attaches to color frame holder and allows for linear beam shaping from four sides-- external equivalent of ellipsoidal shutters

fresnel accessory that attaches to color frame holder and reduces spill and glare from instrument's lens; shape of a tincan

Parabolic Alluminized Reflector

mechanical device. commonly found in followspots, used to dim the light