Illumination – Photographic lighting – Including specific light modifier
Patent
1994-10-14
1996-01-09
Lazarus, Ira S.
Illumination
Photographic lighting
Including specific light modifier
362300, 362348, F21V 700
Patent
active
054834244
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the field of lighting, especially for use in television, filming, theatre and photography.
BACKGROUND ART
In order to soften the shadow edges of high-powered lamps used on film and television sets, it is known to reflect light from the lamps off a reflector onto the subject being lit. The reflecting surface of the reflector is not smooth and so light reaches the subject from several pans of the reflecting surface, thereby giving a soft edge shadow; a crinkled or concave stippled sheet of reflecting material has traditionally been used as the reflecting surface. Such an arrangement has a low efficiency and provides an unsatisfactory penumbra region in the shadow; also a significant proportion of the light emitted from the lighting apparatus is wasted and/or is degraded to heat which must be ventilated from the apparatus.
It is an object of the present invention to provide a lighting apparatus that is effective in producing diffused light without sharp shadows (so-called "soft light").
SUMMARY OF THE INVENTION
According to the present invention there is provided a lighting apparatus for illuminating a subject, which apparatus comprises a reflector for reflecting light, from the towards the subject, the reflector comprising a reflecting surface at least 500 mm in diameter and composed of a plurality of convex light-reflecting elements having a diameter not greater than 20 mm, said light reflecting elements constituting at least 90% (by area) of the reflecting surface.
Light from the individual elements of the reflector will fall on the subject being lit and each element can thus cast a separate shadow; however, if the diameter of each element is sufficiently small, no multiple shadow edge will, in practice, be discernible to an onlooker or, in particular, to a camera filming the scene. We have found that the diameter of each element is preferably less than 15 mm and more preferably is less than 10 mm. If each element is too small, reflecting surface becomes more like a plane surface and so the harder the shadow will appear. We thus prefer that each element is at least 0.5 mm in diameter and preferably more than 1 mm in diameter; we have found that an optimum diameter is in the range of 2 to 10 e.g. 3 to 9 mm.
The reflector can be used to reflect light from an external light source, e.g. the sun, onto the subject being illuminated. However the apparatus will generally include a means for holding a lamp, and in that case the apparatus must include means located in front of the lamp for preventing light from passing directly from the lamp onto the subject; the light preventing means can be a diffuser, e.g. a frosted and/or opalescent screen, that diffuses such direct light or a baffle or reflector that blocks all direct light and generally reflects it back onto the main reflecting surface.
It is preferred that each element is immediately adjacent to all its neighbouring elements and that there are substantially no fiat surfaces between such elements, but up to 10% (by area), and preferably up to 5%, of the reflecting surface can be composed of flat areas. The elements are preferably such that they fit together to form a close-packed arrangement without any flat area between them.
When the elements are all identically shaped the lighting apparatus can give rise to interference patterns and so it is preferable that each element should be surrounded by elements, at least some of which are of a different radius of curvature and/or a different diameter to the element in question.
According to the preferred arrangement, each element may have three to ten neighbouring elements, more generally four to eight neighbouring elements.
The convex shape of each element is preferably such that light falling on any element is not reflected onto an immediately-adjacent element and since this would reduce the efficiency of the reflector
The tangent of each convex element at the place where it meets an adjacent element is preferably at least 25.degree., preferably 45.degree. t
REFERENCES:
patent: 1915842 (1933-06-01), Winkler
patent: 2538638 (1957-01-01), Wilson
patent: 3450459 (1969-06-01), Haggerty
patent: 3671101 (1972-06-01), Finch
patent: 3799646 (1974-03-01), Footchkar
patent: 4035631 (1977-07-01), Day, Jr.
patent: 4209825 (1980-06-01), Shackelford
patent: 4864476 (1989-09-01), Lemons et al.
(2) photographs (show an existing softlight which includes an off-axis light source in conjunction with a plain parabolic reflector).
Kondracki Edward J.
Lazarus Ira S.
Optical & Textile Limited
Raab Sara Sachie
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