UMBRELLA LIGHT
United States Patent 3851164
An umbrella light particularly suitable for motion picture photography. The umbrella has a central portion (adjacent to its apex) whose fabric surfaces face in a direction such as to reflect the light principally in an axial direction, and a peripheral portion whose fabric surfaces face in a direction such as to reflect the light principally in a direction which is radial of the axis. A reflector is situated between the light source and the mouth of the umbrella.
US Patent References:
Indirect or "bounce" lighting apparatus
Hilzen - December 1966 - 3294962
PHOTOGRAPHIC REFLECTING DEVICE
Larson - December 1973 - 3781535
Indirect or "bounce" lighting apparatus
Hilzen - December 1966 - 3294962
PHOTOGRAPHIC REFLECTING DEVICE
Larson - December 1973 - 3781535
Application Number:
05/421516
Publication Date:
11/26/1974
Filing Date:
12/04/1973
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
362/320, 362/17, 362/18
International Classes:
G03B15/03; G03B15/06; G03B15/02; G03B15/02
Field of Search:
240/1.3,1R,2C,2R,103,41.1 135/16
Primary Examiner:
Moses, Richard L.
Attorney, Agent or Firm:
Sheffer, Abner
Claims:
I claim
1. In an umbrella lighting apparatus having a source of continuous light and a foldable umbrella for reflecting light from said source, said umbrella comprising a central shaft, long ribs carrying a light-reflective fabric covering and short ribs connected to said long ribs and said shaft, the improvement wherein said umbrella is so shaped that in its open position it has a central portion, adjacent its apex, whose fabric surface faces in a direction to reflect the light in a direction which is principally axial of said shaft, bounded by a zone whose fabric surface faces in a direction which is principally radial of said shaft, and means for mounting said light source at an axial level which is within said fabric covering.
2. Apparatus as in claim 1 and including a light reflector facing said light source and situated between to said light source and the mouth of said covering to reflect light from said source toward said covering.
3. Apparatus as in claim 2 in which said reflector faces at an acute angle to said shaft.
4. Apparatus as in claim 2 in which said light reflector is a reflective channel adjacent to said light source.
5. Apparatus as in claim 1 in which said light source is situated at a position spaced from the axis of said shaft.
6. Apparatus as in claim 5 comprising a pair of light sources each situated at a position spaced from the axis of said shaft.
7. Apparatus as in claim 6 including means for alternatively activating only one of said sources or both.
8. Apparatus as in claim 2 in which said reflector is so situated that light travelling directly from said light source is not visible at the mouth of said covering.
9. Apparatus as in claim 1 in which the fabric covering is woven of flat metallic reflecting yarns.
10. Apparatus as in claim 9 in which said yarns are about 0.3 to 0.5 mm in width and have their flat faces substantially in the plane of said fabric.
11. Apparatus as in claim 10 in which said yarns are partially covered by multifiber yarns entwined around them.
12. Apparatus as in claim 1 in which said light source comprises a quartz halogen bulb mounted close to, and in fixed relationship to, an elongated metal reflecting surface facing toward said fabric surface, said reflecting surface being positioned to permit passage of light parallel thereto directly from said bulb to said fabric surface.
13. Apparatus as in claim 12 in which said light source consists of two of said quartz halogen bulbs situated on a line which is eccentric of said umbrella.
14. Apparatus as in claim 12 in which said light source and reflector are secured together and secured to a spring clip adapted to be opened manually to provide a side opening larger than the diameter of said umbrella shaft to receive said umbrella shaft and to frictionally engage said umbrella shaft to adjustably fix said light source and reflector on said shaft.
15. Apparatus as in claim 1 in which said light source is mounted less than two feet from said fabric surface, said fabric having a weight of less than about 5 ounces per square yard and being woven of flat metallic reflecting yarns running in one direction of said weave and having their flat metallic faces substantially in the plane of said fabric.
16. Apparatus as in claim 1, said metallic faces being visible principally on the concave side of the umbrella.
17. Apparatus as in claim 15 including a light reflector facing said light source and situated between said light source and the mouth of said covering to reflect light from said source toward said covering, and in which said reflector faces at an acute angle to said shaft, said light reflector is a reflective channel adjacent to said light source, said reflector is so situated that light travelling directly from said light source is not visible at the mouth of said covering, and said light source comprises a quartz halogen bulb.
18. Apparatus as in claim 17, having a pair of said light sources each situated at a position spaced from the axis of said shaft and on a line which is eccentric of said umbrella, said light sources and reflectors being secured together and secured to a spring clip adapted to be opened manually to provide a side opening larger than the diameter of said umbrella shaft to receive said umbrella shaft and to frictionally engage said umbrella shaft to adjustably fix said light source and reflector on said shaft.
19. Apparatus as in claim 8 in which the fabric covering is woven of flat metallic reflecting yarns about 0.3 to 0.5 mm in width and having their flat faces substantially in the plane of said fabric, said light source being a quartz halogen bulb.
20. Apparatus as in claim 19 in which said light source is situated at a position spaced from the axis of said shaft, said reflector faces at an acute angle to said shaft, said light reflector is a reflective channel adjacent to said light source.
1. In an umbrella lighting apparatus having a source of continuous light and a foldable umbrella for reflecting light from said source, said umbrella comprising a central shaft, long ribs carrying a light-reflective fabric covering and short ribs connected to said long ribs and said shaft, the improvement wherein said umbrella is so shaped that in its open position it has a central portion, adjacent its apex, whose fabric surface faces in a direction to reflect the light in a direction which is principally axial of said shaft, bounded by a zone whose fabric surface faces in a direction which is principally radial of said shaft, and means for mounting said light source at an axial level which is within said fabric covering.
2. Apparatus as in claim 1 and including a light reflector facing said light source and situated between to said light source and the mouth of said covering to reflect light from said source toward said covering.
3. Apparatus as in claim 2 in which said reflector faces at an acute angle to said shaft.
4. Apparatus as in claim 2 in which said light reflector is a reflective channel adjacent to said light source.
5. Apparatus as in claim 1 in which said light source is situated at a position spaced from the axis of said shaft.
6. Apparatus as in claim 5 comprising a pair of light sources each situated at a position spaced from the axis of said shaft.
7. Apparatus as in claim 6 including means for alternatively activating only one of said sources or both.
8. Apparatus as in claim 2 in which said reflector is so situated that light travelling directly from said light source is not visible at the mouth of said covering.
9. Apparatus as in claim 1 in which the fabric covering is woven of flat metallic reflecting yarns.
10. Apparatus as in claim 9 in which said yarns are about 0.3 to 0.5 mm in width and have their flat faces substantially in the plane of said fabric.
11. Apparatus as in claim 10 in which said yarns are partially covered by multifiber yarns entwined around them.
12. Apparatus as in claim 1 in which said light source comprises a quartz halogen bulb mounted close to, and in fixed relationship to, an elongated metal reflecting surface facing toward said fabric surface, said reflecting surface being positioned to permit passage of light parallel thereto directly from said bulb to said fabric surface.
13. Apparatus as in claim 12 in which said light source consists of two of said quartz halogen bulbs situated on a line which is eccentric of said umbrella.
14. Apparatus as in claim 12 in which said light source and reflector are secured together and secured to a spring clip adapted to be opened manually to provide a side opening larger than the diameter of said umbrella shaft to receive said umbrella shaft and to frictionally engage said umbrella shaft to adjustably fix said light source and reflector on said shaft.
15. Apparatus as in claim 1 in which said light source is mounted less than two feet from said fabric surface, said fabric having a weight of less than about 5 ounces per square yard and being woven of flat metallic reflecting yarns running in one direction of said weave and having their flat metallic faces substantially in the plane of said fabric.
16. Apparatus as in claim 1, said metallic faces being visible principally on the concave side of the umbrella.
17. Apparatus as in claim 15 including a light reflector facing said light source and situated between said light source and the mouth of said covering to reflect light from said source toward said covering, and in which said reflector faces at an acute angle to said shaft, said light reflector is a reflective channel adjacent to said light source, said reflector is so situated that light travelling directly from said light source is not visible at the mouth of said covering, and said light source comprises a quartz halogen bulb.
18. Apparatus as in claim 17, having a pair of said light sources each situated at a position spaced from the axis of said shaft and on a line which is eccentric of said umbrella, said light sources and reflectors being secured together and secured to a spring clip adapted to be opened manually to provide a side opening larger than the diameter of said umbrella shaft to receive said umbrella shaft and to frictionally engage said umbrella shaft to adjustably fix said light source and reflector on said shaft.
19. Apparatus as in claim 8 in which the fabric covering is woven of flat metallic reflecting yarns about 0.3 to 0.5 mm in width and having their flat faces substantially in the plane of said fabric, said light source being a quartz halogen bulb.
20. Apparatus as in claim 19 in which said light source is situated at a position spaced from the axis of said shaft, said reflector faces at an acute angle to said shaft, said light reflector is a reflective channel adjacent to said light source.
Description:
This invention relates to an umbrella light particularly suitable for use in motion picture photography.
The use of umbrella lights is well known in photography. Commercial still photographers employ them, usually with stroboscopic light sources. For motion picture photography, in which a continuous light is needed, umbrella lights have not been found to be suitable. For one thing, they have not been able to provide sufficient light. Their light efficiency has been very low; in addition directional control and masking (or area limitation) have been very awkward.
In accordance with one aspect of this invention there is provided a highly efficient umbrella light which gives a desirable "soft light" which is comparatively shadowless and even and covers a very large area. Thus the umbrella light specifically described herein provides a soft light covering an area of about 80 square feet at a distance of 8 feet with an even distribution of 160 foot candles per square foot (and also strongly illuminating a larger area, the flat area over all of which the light intensity is at least half of that at beam center being about 300 square feet, which contributes to the "softness"). while drawing only 10 amperes, when both bulbs are lit; when only one bulb is lit, the same results are obtained but the light output and current are halved. At different distances, about the same area is illuminated and the illumination is similarly even. It can be set up (and dismantled) within less than a minute (e.g. about 20 seconds). It can be adjusted to any angle within 270° in vertical plane and 360° in a horizontal plane, and even with the use of an extremely light weight stand it can be raised to a considerable height above ground, e.g. about 11 feet.
In the accompanying drawings which illustrate one aspect of the invention,
FIG. 1 is a view looking axially into the mouth of the umbrella, with one of its lamps lit.
FIG. 2 is a side view of a light source and reflector unit secured to the umbrella shaft.
FIG. 3 is a front view of the light-emitting side of the light source and reflector unit.
FIG. 4 is a view, from below, of a portion of the same unit, secured to the umbrella shaft, with a portion broken away to illustrate the position of one of the lamps.
FIG. 5 is a view (with the umbrella fabric in cross section), showing the construction and mounting of the umbrella.
FIG. 6 is a plan view of a fabric panel.
FIG. 7 is a view showing the positions of the umbrella ribs when the umbrella is partly open, at a position in which its mouth has substantially its maximum diameter while its long ribs are still straight (and the fabric between said ribs is still slack except at said mouth).
FIG. 8 is a schematic view showing a less preferred arrangement in which the umbrella shaft, rather than the light source and reflector unit, is directly secured to a swivel on the stand.
FIG. 9 is a view looking along the umbrella shaft and showing the positioning of a light filter.
FIG. 10 is a view at right angle to FIG. 9.
FIG. 11 is a schematic end view showing the configuration of one form of reflector.
In the drawings reference numeral 11 designates a light source and reflector unit adjustably fixed to the axial shaft 12 of a foldable umbrella-type reflector 13. The assemblage of umbrella-type reflector 13 and light source unit 11 is adjustably supported on a swivel 14 atop a conventional folding tripod stand 16 having an adjustable telescoping vertical pole 17.
The unit 11 comprises a pair of quartz halogen lamps 18, 18a (see FIGS. 2-4) mounted in oppositely facing sockets 19, 19a, respectively, and a corresponding pair of reflectors, 21, 21a, respectively. Each of the reflectors is preferably channel-shaped, more preferably a substantially symmetrical channel. In a particularly suitable form the channel has three substantially planar reflecting areas, 22, 23, 24 (or 22a, 23a, 24a). The planar area 22 (or 22a) of largest area is in a plane which faces outwardly from the axis of the umbrella shaft, the angle α shown in FIG. 4 (between the projection of that plane and the shaft) being about 80°. The two other planar areas 23 (or 23a) and 24 (or 24a) are roughly transverse to the area 22 (or 22a). As described below each channel-shaped reflector can be fabricated simply from a rectangular piece of reflector metal such as high purity specular aluminum reflective sheeting (such as King Lux or Alzac, having an expanded surface area and a specular surface finish, e.g. clear anodized with 97 percent reflectance, about 0.016 inch thick having a hammered surface, e.g. with depression about 2 mm deep and about 3 to 5 mm across).
In the illustrated embodiment the sockets 19, 19a and reflectors 21, 21a are fixed to the housing 25 of a switch box 26 which contains a three position switch 27 (e.g. a double pole double throw switch) so that the line voltage can be applied to (a) both lamps in parallel, (b) one lamp, 18a only, or (c) neither lamp. Wires 28, 29 connect the switch to the sockets 19, 19a; a lamp cord 31 (of the type suitable for high temperature service, with appropriate conventional strain relief) adapted to be plugged into a suitable receptacle providing electric power extends from the switch.
The unit 11, having the lamps and reflectors in predetermined fixed relationship, is adapted to be secured at any suitable position along the length of the umbrella shaft 12. To this end it has a spring clamp 32 for frictionally engaging the shaft 12, the clamp 32 being secured to the switch box housing at a position for holding said shaft midway between the bulbs 18, 18a. Although the bulbs and their reflectors are thus not arranged completely symmetrically with respect to the shaft 12 and the umbrella-type reflector carried thereby (e.g. when the shaft 12 is horizontal both bulbs and both reflectors are below the shaft, with both bulb filaments being, say, about 1 to 5 cm below the shaft) it is found that this asymmetry has substantially no detrimental effect on the intensity or quality of the light output.
The spring clamp may be a simple conventional spring clip such as is used for holding sheets of paper together, having a pair of spring-loaded jaws 33, 34 generally several cm (e.g. about 5 cm) long and having a pair of finger pieces 35, 36 (e.g. "Boston Clip No. 2" of Hunt Mfg. Co.). One of the finger pieces 35 is secured to the switch box housing; the other, 36, projects outwards for manual manipulation and is provided with a heat- and electrically-insulating covering 37.
As indicated, each reflector 21 (or 21a) may be constructed from a rectangular sheet of reflecting material by bending the sheet to channel form and slitting the sheet a short distance along each bend line, as indicated at 39 and 39a, so that the central planar portion adjacent the slit can be secured (with the lamp socket 19, or 19a) to a face 41 of switch housing 25 which is to be perpendicular to the axial shaft 12 of the umbrella while the remainder of the channel can be tilted at an angle to said shaft by slightly bending said central planar portion along a line joining the ends of said slits (thus opening the slits as indicated). A channel shaped bridging piece 42 is secured to both bent reflectors to help keep them in the illustrated positions; preferably this bridging piece is also made of highly reflective aluminum and, while serving as a cover for the wiring and a structural stay, also serves to increase the useful reflective surface.
In the illustrated embodiment the lamps are of the type designated as "DY" in the trade (specifically "DYH," others which may be used being "DYN," "DYA," etc.). As shown, the lamps may have filaments which are formed of thin wire tightly coiled into helical form so as to form a thicker structure, which thicker structure is in turn formed into a much looser helix [shown schematically at 85, 85a], e.g. of 6 turns extending over a length of about 1 cm with the external diameter of the helix being about 1/2 cm, the lamps being mounted so that this looser helix has a more or less vertical axis when the umbrella shaft 12 is substantially horizontal. In the illustrated embodiment the looser helix of the filmanet is situated about midway of the effective length of the reflector 21 or 21a (which, as illustrated, is about 71/2 cm) and also about midway of its effective width (which, as illustrated, is about 5 to 6 cm), the channel-shaped reflector is open-ended, and the lamps (and their filaments) are relatively close to the respective reflector surfaces 22, 22a (e.g. the distance between the filament helixes 85, 85a and the respective reflector surfaces 22, 22a is well below 3 cm, such as about 2 cm and the distance between the closest points of the quartz envelopes of the lamps and those reflector surfaces is well below 1 cm, such as about 1/2 cm or less). The construction provides the appropriate convection cooling needed by quartz-halogen lamps to avoid failure from overheating and blackening from operation at undesirably low temperatures, while giving very high reflection and utilization of the light from the lamps, but avoiding direct illumination of the subject to be photographed since the position of the reflector unit is generally such that all the light passing directly from the filament hits either the metal reflector 21 (or 21a) or the umbrella type reflector 13. As indicated above, the channel walls need not be at right angles to each other as shown in FIG. 2; in one preferred construction (illustrated schematically in FIG. 11), the side walls 23 (or 23a) and 24 (and 24a) of the channel diverge away from its base wall 22 (or 22a) e.g., they are at angles of about 60° to 80° to said base wall.
In a most preferred form of the invention, the lamp-reflector unit 11 is (as illustrated in FIG. 2) fixed to the swivel 14 atop the folding stand 16. It will be seen that the center of gravity of the device is situated approximately directly over the pole 17. (It is also within the broader scope of the invention to have the umbrella shaft 12 fixed to said swivel 14, as illustrated schematically in FIG. 8.) The swivel may comprise a sleeve 43 adapted to be rotated about a vertical upstanding pin 44 projecting from the top of the pole 17 and to be held thereon by a set screw, e.g. a thumb or wing screw. Fixed to the top of the sleeve is a slit block 45 serving as a clampable bearing for a horizontal pin 46 fixed to the depending ears 47 of a clevis bracket 48 attached to housing 25; the block has a slit 49 so that the portion 51 thereof on one side of the slit can be moved slightly toward the portion 52 on the other side thereof so as to clamp the horizontal pin 47 in any desired position, such movement being effected by a thumbscrew 53 threaded into portion 51 and having its shank passing freely through a hole in the other portion 52.
Like conventional umbrellas, the umbrella has, on its central shaft 12, a small ring 56 fixed near the top of the shaft; a set of long ribs 57 each having one end 58 pivotally attached to the small fixed ring 56; a slider 59 mounted on the shaft and having a small ring 61 integral therewith; a set of short ribs 62 each having one of its ends 63 pivotally attached to the slider ring and its other end 64 pivotally attached to the long rib at an intermediate point 66 on the length of said long rib 57 (a pivot fitting 67 being fixed to each long rib for this purpose); a latch 68 to hold the slider 59 in a position on the shaft in which the umbrella is open; a second latch 68a to hold the slider in a position on the shaft in which the umbrella is closed; and a fabric cover 69 which is fixed to the shaft just outside of the fixed ring 58 (being held on the shaft by a suitable ferrule 71) and is attached (as by suitable thread loops 72) to fittings 73 secured to the long ribs 57 adjacent their free ends 74, as well as by intermediate thread loops 76 engaging intermediate portions of said long ribs. As in conventional umbrellas, the covering is made up of a series of substantially identical sectors or panels sewn together along their edges, forming seams, and the rib-attaching loops 72 are situated at the outer ends of the seams so that each of the panels is disposed between the corresponding adjacent long ribs. The position of the latch 68 is such that when the slider is held thereby the fabric is taut and the long ribs are bent. The ribs are flexible and of conventional construction, of thin metal which is formed into channel-shaped cross-section over substantially their whole length, except at their ends.
The fabric panels 78 (FIG. 6) are in the general shape of isosceles triangles. In the illustrated embodiment the short base 79 of each triangle is not straight but concave. This concave base has a sewn hem.
The umbrella is so shaped that in its open operative position it has a central portion, adjacent to its apex, whose fabric surface faces in a direction such as to reflect the light principally in an axial direction and a peripheral portion whose fabric surfaces face in a direction such as to reflect the light principally in a direction which is radial of the axis. In the illustrated embodiment the fabric covering has a central portion 81 where each long rib has substantially uniform radius of curvature, bounded by a relatively narrow zone or band 82 where each long rib has a smaller radius of curvature which is in turn bounded by a zone or band 83 where each long rib has a much larger radius of curvature. The portion or large radius of curvature faces generally radially of the axis and may extend over an axial length a plurality of times greater than the other portions of the covering. Thus in a very suitable embodiment the radius of curvature of the central portion 81 is about 3 feet, the radius of curvature of the band 82 is about 20 inches and the radius of curvature of the band 83 is about 10 feet. More specifically in that embodiment there are eight identical long ribs 57 and an equal number of identical short ribs 62 and identical panels 78 arranged symmetrically; the length of each long rib (between the pivot point at ring 56 and the point of attachment [(loop 72)] of the fabric) is about 241/2 inches; the length of each short rib 62 is about 8 inches; the length of each long rib 57 between pivot points 58 and 66 is about 8 inches; the pivot radius of each ring is about 7 mm; and the location of the latch 68 is such that the slider ring pivots 63 are about 41/4 inches from the fixed ring pivots 58 when the umbrella is in its fully open condition.
In the illustrated embodiment, the fabric is so dimensioned that when the umbrella is in fully open condition the straight-line distance between the fabric-attachment points (loops 72) on adjacent long ribs is about 111/2 inches and the distance from the axis of the shaft 12 to said fabric attachment points is about 151/2 inches, and those fabric-attachment points are situated at a level which is about 16 inches (measured axially along the shaft) from the stationary ring pivot points. Thus the diameter of the mouth of the fully opened umbrella is about 31 inches and the ratio of this mouth diameter to the fabric length (measured along a rib) is about 31:24.5 or about 1.2:1; preferably this ratio is below 1.4:1 still more preferably below 1.3:1 and usually it is above 0.9:1 or 1:1.
When the umbrella is in folded condition its ribs are straight. As is conventional, to open the umbrella one moves the slider 59 axially. At first this movement causes separation of the long ribs without bending them (see FIG. 7), until the further outward movement of the free ends of the long ribs is restrained because the fabric at the bases 79 of the sectors 78 has become taut; in other words, the mouth of the umbrella has attained its greatest circumference (and diameter). Further axial movement of the slider and resulting outward movement of the ends 64 of the short ribs 62 does not increase the diameter of the mouth of the umbrella but does cause outward bending of the intermediate portions of the ribs and thus makes taut the whole fabric cover. The short ribs remain substantially straight during this operation.
The fabric 69 is of flexible reflective material. A particularly suitable fabric is woven of flat silvery metal yarns, such as aluminum foil yarns of known type. One such fabric found especially useful has the aluminum yarns in its weft. The flat yarns having their flat faces arranged substantially parallel to the plane of the fabric, with said weft yarns running in a direction generally parallel to the line bisecting the apex angle β of the triangular panel (i.e., in the direction parallel to that shown by the arrows in FIG. 6). The weave pattern is such that (although both sides of the flat aluminum yarns have similar reflectances) the shiny aluminum yarns are visible principally on one side of the fabric and are principally covered by the warp yarns on the other side. Thus the fabric may have a construction in which there are floats of yarns spanning a plurality of crossing yarns, e.g. it may be a satin or sateen. The metallic yarns are preferably of the supported type (e.g. a 1 end combined Lurex yarn as described at pages 136-139 of Man-Made Textile Encyclopedia edited by J. J. Press, pub. 1959 by Textile Book Publishers Inc.). In one suitable fabric the metallic yarns are about 1/64 inch wide (i.e., about 0.4 mm), have a multifilament (e.g. 20 filament rayon) yarn entwined around them, and are woven about 50-60 per inch, and the warp yarns are of rayon, woven (at right angles to the weft) about 80 per inch, the weave pattern being a 4/1 sateen. The shiny side, on which the metallic yarns are visible, preferably forms the inner surface of the umbrella reflector; good results have also been obtained even when the duller side is used as the inside. The fabric need not be opaque; thus very good results have been obtained with a fabric which, like that just described, transmits some 20 to 50 percent of the incident light. The intense heat from the quartz-halogen lamp is carried away and dissipated over a large area by the metal yarns and by the passage of convection currents of air around the light source and through interstices of the fabric.
As previously described, the unit 11 may be secured at various positions along the length of the umbrella shaft. For maximum light efficiency there is an optimum position. This is found to be at a location at which the filament helix 85 (or 85a) of the light bulb, and the surface of the adjacent reflector 21 (or 21a), are well within the fabric enclosure, i.e., at a level (measured axially of said shaft) which is well inward of the level of the fabric-attaching loops, especially at a point at which said filament is located at about the focal point of the portion of the intermediate band 82 adjacent thereto. Thus, for the construction specifically described above, a particularly suitable position is one in which the distance from the filament to the closest surfaces of the fabric is about 91/2 inches (which is about one half the radius of curvature of said intermediate band). Bringing the unit 11 further into the enclosure gives a "harder" light (i.e., a light which casts more sharply defined and darker shadows) while moving it further away from the ring 61 makes the light softer. There is an indicator 86 on shaft 12 to show the optimum location for the clamp 32.
When an observer looks axially into the mouth of the umbrella specifically described above, say from a distance of about 10 feet from the lamps 18, 18a, with one lamp 18a lit, he sees (FIG. 1) a very brightly lit inner zone 88 extending from the apex of the fabric cover (in a direction towards the observer) about half the length of the ribs, surrounded by a less brightly lit (or shadowed) outer ring 89 on the balance of the reflector. In the brightly lit inner zone each of the panels has a large elongated very bright band 91 so that there are eight such separate bright bands visible. When both lamps are lit the effect is similar but instead of a single bright band in panel there are a pair of such bright bands or a broader bright band.
The device as described above gives light having a color temperature of about 3,200°K, suitable for indoor photography. It may also be simply adapted to give a color temperature of, say, about 5,500°K for use with daylight-type photographic film, by mounting a blue filter between the light source and the light reflecting fabric 69. This may be a sheet 96 (FIGS. 9 and 10) of blue plastic (e.g. nylon) film having secured thereto a hanger or clamp 97 for supporting it on the shaft 12. In one preferred form illustrated in FIGS. 9 and 10 the sheet 96 is rectangular, slightly larger (e.g. about 1 inch larger on each side) than the axially projected reflective area of the unit 11, and mounted a few inches (e.g. 3 inches) from the closest portions of unit 11. With this construction most of the light given off by the light source passes through the sheet 96 which absorbs the red wavelengths but a portion travels directly to the fabric 69. This enables one to get the light effect of a blue sky with bright sunlight, using a filter which ordinarily produces a light that is bluer than ordinary daylight. One use for this modification is in outdoor motion picture photography to make objects in the shadows more visible by using the umbrella light as a supplement to natural light.
Reference is made to my earlier U.S. Pat. No. 3,437,802, which describes characteristics of quartz halogen lamps, and to U.S. Pat. No. 3,294,962 relating to an umbrella type lighting apparatus employing certain halogen quartz lamps.
As can be seen in the drawings, in a preferred form of the invention the size, shape and position of the switch box 26 are such that it lies substantially entirely behind the reflectors 21, 21a and reflective bridging piece 42, and thus does not act to block or absorb a significant portion of the light travelling axially from the fabric covering toward the mouth of the umbrella. In the illustrated construction the face of bridging piece 42 has a length of about 31/4 inches and a width of about 2 inches, and the total area of reflectors 21, 21a and bridging piece 42 (measured as projected in a direction parallel to the axis of shaft 12) is in the neighborhood of 25 to 30 square inches, which is well below 10 percent and even below 5 percent of the area at the mouth of the umbrella (which is in the neighborhood of 700 to 800 square inches). It is within the broader scope of the invention, however, for the reflectors and bridging piece to cover a larger proportion of the area.
It is noted that the manufacturer's instructions accompanying General Electric DYH quartz halogen lamps specify "Do not direct beam at persons and materials from less than four feet." As indicated above, the distance from the lamp to the closest portions of the umbrella fabric is generally much less than two feet, usually less than about 1 foot and above about 1/2 foot. Yet the fabric does not become uncomfortably warm to the touch, much less reach the danger level, despite the flammability or charability of the fabric. Generally the fabric is of lighweight construction, having a weight well below 10, usually below about 5, ounces per square yard, such as about 3 to 4 ounces per square yard. In the preferred construction the reflectors 21,21a are substantially non-concentrating or non-condensing; they gather the light but do not focus it.
It is understood that the foregoing detailed description is given merely by way of illustration and that variations may be made therein without departing from the spirit of the invention.
The use of umbrella lights is well known in photography. Commercial still photographers employ them, usually with stroboscopic light sources. For motion picture photography, in which a continuous light is needed, umbrella lights have not been found to be suitable. For one thing, they have not been able to provide sufficient light. Their light efficiency has been very low; in addition directional control and masking (or area limitation) have been very awkward.
In accordance with one aspect of this invention there is provided a highly efficient umbrella light which gives a desirable "soft light" which is comparatively shadowless and even and covers a very large area. Thus the umbrella light specifically described herein provides a soft light covering an area of about 80 square feet at a distance of 8 feet with an even distribution of 160 foot candles per square foot (and also strongly illuminating a larger area, the flat area over all of which the light intensity is at least half of that at beam center being about 300 square feet, which contributes to the "softness"). while drawing only 10 amperes, when both bulbs are lit; when only one bulb is lit, the same results are obtained but the light output and current are halved. At different distances, about the same area is illuminated and the illumination is similarly even. It can be set up (and dismantled) within less than a minute (e.g. about 20 seconds). It can be adjusted to any angle within 270° in vertical plane and 360° in a horizontal plane, and even with the use of an extremely light weight stand it can be raised to a considerable height above ground, e.g. about 11 feet.
In the accompanying drawings which illustrate one aspect of the invention,
FIG. 1 is a view looking axially into the mouth of the umbrella, with one of its lamps lit.
FIG. 2 is a side view of a light source and reflector unit secured to the umbrella shaft.
FIG. 3 is a front view of the light-emitting side of the light source and reflector unit.
FIG. 4 is a view, from below, of a portion of the same unit, secured to the umbrella shaft, with a portion broken away to illustrate the position of one of the lamps.
FIG. 5 is a view (with the umbrella fabric in cross section), showing the construction and mounting of the umbrella.
FIG. 6 is a plan view of a fabric panel.
FIG. 7 is a view showing the positions of the umbrella ribs when the umbrella is partly open, at a position in which its mouth has substantially its maximum diameter while its long ribs are still straight (and the fabric between said ribs is still slack except at said mouth).
FIG. 8 is a schematic view showing a less preferred arrangement in which the umbrella shaft, rather than the light source and reflector unit, is directly secured to a swivel on the stand.
FIG. 9 is a view looking along the umbrella shaft and showing the positioning of a light filter.
FIG. 10 is a view at right angle to FIG. 9.
FIG. 11 is a schematic end view showing the configuration of one form of reflector.
In the drawings reference numeral 11 designates a light source and reflector unit adjustably fixed to the axial shaft 12 of a foldable umbrella-type reflector 13. The assemblage of umbrella-type reflector 13 and light source unit 11 is adjustably supported on a swivel 14 atop a conventional folding tripod stand 16 having an adjustable telescoping vertical pole 17.
The unit 11 comprises a pair of quartz halogen lamps 18, 18a (see FIGS. 2-4) mounted in oppositely facing sockets 19, 19a, respectively, and a corresponding pair of reflectors, 21, 21a, respectively. Each of the reflectors is preferably channel-shaped, more preferably a substantially symmetrical channel. In a particularly suitable form the channel has three substantially planar reflecting areas, 22, 23, 24 (or 22a, 23a, 24a). The planar area 22 (or 22a) of largest area is in a plane which faces outwardly from the axis of the umbrella shaft, the angle α shown in FIG. 4 (between the projection of that plane and the shaft) being about 80°. The two other planar areas 23 (or 23a) and 24 (or 24a) are roughly transverse to the area 22 (or 22a). As described below each channel-shaped reflector can be fabricated simply from a rectangular piece of reflector metal such as high purity specular aluminum reflective sheeting (such as King Lux or Alzac, having an expanded surface area and a specular surface finish, e.g. clear anodized with 97 percent reflectance, about 0.016 inch thick having a hammered surface, e.g. with depression about 2 mm deep and about 3 to 5 mm across).
In the illustrated embodiment the sockets 19, 19a and reflectors 21, 21a are fixed to the housing 25 of a switch box 26 which contains a three position switch 27 (e.g. a double pole double throw switch) so that the line voltage can be applied to (a) both lamps in parallel, (b) one lamp, 18a only, or (c) neither lamp. Wires 28, 29 connect the switch to the sockets 19, 19a; a lamp cord 31 (of the type suitable for high temperature service, with appropriate conventional strain relief) adapted to be plugged into a suitable receptacle providing electric power extends from the switch.
The unit 11, having the lamps and reflectors in predetermined fixed relationship, is adapted to be secured at any suitable position along the length of the umbrella shaft 12. To this end it has a spring clamp 32 for frictionally engaging the shaft 12, the clamp 32 being secured to the switch box housing at a position for holding said shaft midway between the bulbs 18, 18a. Although the bulbs and their reflectors are thus not arranged completely symmetrically with respect to the shaft 12 and the umbrella-type reflector carried thereby (e.g. when the shaft 12 is horizontal both bulbs and both reflectors are below the shaft, with both bulb filaments being, say, about 1 to 5 cm below the shaft) it is found that this asymmetry has substantially no detrimental effect on the intensity or quality of the light output.
The spring clamp may be a simple conventional spring clip such as is used for holding sheets of paper together, having a pair of spring-loaded jaws 33, 34 generally several cm (e.g. about 5 cm) long and having a pair of finger pieces 35, 36 (e.g. "Boston Clip No. 2" of Hunt Mfg. Co.). One of the finger pieces 35 is secured to the switch box housing; the other, 36, projects outwards for manual manipulation and is provided with a heat- and electrically-insulating covering 37.
As indicated, each reflector 21 (or 21a) may be constructed from a rectangular sheet of reflecting material by bending the sheet to channel form and slitting the sheet a short distance along each bend line, as indicated at 39 and 39a, so that the central planar portion adjacent the slit can be secured (with the lamp socket 19, or 19a) to a face 41 of switch housing 25 which is to be perpendicular to the axial shaft 12 of the umbrella while the remainder of the channel can be tilted at an angle to said shaft by slightly bending said central planar portion along a line joining the ends of said slits (thus opening the slits as indicated). A channel shaped bridging piece 42 is secured to both bent reflectors to help keep them in the illustrated positions; preferably this bridging piece is also made of highly reflective aluminum and, while serving as a cover for the wiring and a structural stay, also serves to increase the useful reflective surface.
In the illustrated embodiment the lamps are of the type designated as "DY" in the trade (specifically "DYH," others which may be used being "DYN," "DYA," etc.). As shown, the lamps may have filaments which are formed of thin wire tightly coiled into helical form so as to form a thicker structure, which thicker structure is in turn formed into a much looser helix [shown schematically at 85, 85a], e.g. of 6 turns extending over a length of about 1 cm with the external diameter of the helix being about 1/2 cm, the lamps being mounted so that this looser helix has a more or less vertical axis when the umbrella shaft 12 is substantially horizontal. In the illustrated embodiment the looser helix of the filmanet is situated about midway of the effective length of the reflector 21 or 21a (which, as illustrated, is about 71/2 cm) and also about midway of its effective width (which, as illustrated, is about 5 to 6 cm), the channel-shaped reflector is open-ended, and the lamps (and their filaments) are relatively close to the respective reflector surfaces 22, 22a (e.g. the distance between the filament helixes 85, 85a and the respective reflector surfaces 22, 22a is well below 3 cm, such as about 2 cm and the distance between the closest points of the quartz envelopes of the lamps and those reflector surfaces is well below 1 cm, such as about 1/2 cm or less). The construction provides the appropriate convection cooling needed by quartz-halogen lamps to avoid failure from overheating and blackening from operation at undesirably low temperatures, while giving very high reflection and utilization of the light from the lamps, but avoiding direct illumination of the subject to be photographed since the position of the reflector unit is generally such that all the light passing directly from the filament hits either the metal reflector 21 (or 21a) or the umbrella type reflector 13. As indicated above, the channel walls need not be at right angles to each other as shown in FIG. 2; in one preferred construction (illustrated schematically in FIG. 11), the side walls 23 (or 23a) and 24 (and 24a) of the channel diverge away from its base wall 22 (or 22a) e.g., they are at angles of about 60° to 80° to said base wall.
In a most preferred form of the invention, the lamp-reflector unit 11 is (as illustrated in FIG. 2) fixed to the swivel 14 atop the folding stand 16. It will be seen that the center of gravity of the device is situated approximately directly over the pole 17. (It is also within the broader scope of the invention to have the umbrella shaft 12 fixed to said swivel 14, as illustrated schematically in FIG. 8.) The swivel may comprise a sleeve 43 adapted to be rotated about a vertical upstanding pin 44 projecting from the top of the pole 17 and to be held thereon by a set screw, e.g. a thumb or wing screw. Fixed to the top of the sleeve is a slit block 45 serving as a clampable bearing for a horizontal pin 46 fixed to the depending ears 47 of a clevis bracket 48 attached to housing 25; the block has a slit 49 so that the portion 51 thereof on one side of the slit can be moved slightly toward the portion 52 on the other side thereof so as to clamp the horizontal pin 47 in any desired position, such movement being effected by a thumbscrew 53 threaded into portion 51 and having its shank passing freely through a hole in the other portion 52.
Like conventional umbrellas, the umbrella has, on its central shaft 12, a small ring 56 fixed near the top of the shaft; a set of long ribs 57 each having one end 58 pivotally attached to the small fixed ring 56; a slider 59 mounted on the shaft and having a small ring 61 integral therewith; a set of short ribs 62 each having one of its ends 63 pivotally attached to the slider ring and its other end 64 pivotally attached to the long rib at an intermediate point 66 on the length of said long rib 57 (a pivot fitting 67 being fixed to each long rib for this purpose); a latch 68 to hold the slider 59 in a position on the shaft in which the umbrella is open; a second latch 68a to hold the slider in a position on the shaft in which the umbrella is closed; and a fabric cover 69 which is fixed to the shaft just outside of the fixed ring 58 (being held on the shaft by a suitable ferrule 71) and is attached (as by suitable thread loops 72) to fittings 73 secured to the long ribs 57 adjacent their free ends 74, as well as by intermediate thread loops 76 engaging intermediate portions of said long ribs. As in conventional umbrellas, the covering is made up of a series of substantially identical sectors or panels sewn together along their edges, forming seams, and the rib-attaching loops 72 are situated at the outer ends of the seams so that each of the panels is disposed between the corresponding adjacent long ribs. The position of the latch 68 is such that when the slider is held thereby the fabric is taut and the long ribs are bent. The ribs are flexible and of conventional construction, of thin metal which is formed into channel-shaped cross-section over substantially their whole length, except at their ends.
The fabric panels 78 (FIG. 6) are in the general shape of isosceles triangles. In the illustrated embodiment the short base 79 of each triangle is not straight but concave. This concave base has a sewn hem.
The umbrella is so shaped that in its open operative position it has a central portion, adjacent to its apex, whose fabric surface faces in a direction such as to reflect the light principally in an axial direction and a peripheral portion whose fabric surfaces face in a direction such as to reflect the light principally in a direction which is radial of the axis. In the illustrated embodiment the fabric covering has a central portion 81 where each long rib has substantially uniform radius of curvature, bounded by a relatively narrow zone or band 82 where each long rib has a smaller radius of curvature which is in turn bounded by a zone or band 83 where each long rib has a much larger radius of curvature. The portion or large radius of curvature faces generally radially of the axis and may extend over an axial length a plurality of times greater than the other portions of the covering. Thus in a very suitable embodiment the radius of curvature of the central portion 81 is about 3 feet, the radius of curvature of the band 82 is about 20 inches and the radius of curvature of the band 83 is about 10 feet. More specifically in that embodiment there are eight identical long ribs 57 and an equal number of identical short ribs 62 and identical panels 78 arranged symmetrically; the length of each long rib (between the pivot point at ring 56 and the point of attachment [(loop 72)] of the fabric) is about 241/2 inches; the length of each short rib 62 is about 8 inches; the length of each long rib 57 between pivot points 58 and 66 is about 8 inches; the pivot radius of each ring is about 7 mm; and the location of the latch 68 is such that the slider ring pivots 63 are about 41/4 inches from the fixed ring pivots 58 when the umbrella is in its fully open condition.
In the illustrated embodiment, the fabric is so dimensioned that when the umbrella is in fully open condition the straight-line distance between the fabric-attachment points (loops 72) on adjacent long ribs is about 111/2 inches and the distance from the axis of the shaft 12 to said fabric attachment points is about 151/2 inches, and those fabric-attachment points are situated at a level which is about 16 inches (measured axially along the shaft) from the stationary ring pivot points. Thus the diameter of the mouth of the fully opened umbrella is about 31 inches and the ratio of this mouth diameter to the fabric length (measured along a rib) is about 31:24.5 or about 1.2:1; preferably this ratio is below 1.4:1 still more preferably below 1.3:1 and usually it is above 0.9:1 or 1:1.
When the umbrella is in folded condition its ribs are straight. As is conventional, to open the umbrella one moves the slider 59 axially. At first this movement causes separation of the long ribs without bending them (see FIG. 7), until the further outward movement of the free ends of the long ribs is restrained because the fabric at the bases 79 of the sectors 78 has become taut; in other words, the mouth of the umbrella has attained its greatest circumference (and diameter). Further axial movement of the slider and resulting outward movement of the ends 64 of the short ribs 62 does not increase the diameter of the mouth of the umbrella but does cause outward bending of the intermediate portions of the ribs and thus makes taut the whole fabric cover. The short ribs remain substantially straight during this operation.
The fabric 69 is of flexible reflective material. A particularly suitable fabric is woven of flat silvery metal yarns, such as aluminum foil yarns of known type. One such fabric found especially useful has the aluminum yarns in its weft. The flat yarns having their flat faces arranged substantially parallel to the plane of the fabric, with said weft yarns running in a direction generally parallel to the line bisecting the apex angle β of the triangular panel (i.e., in the direction parallel to that shown by the arrows in FIG. 6). The weave pattern is such that (although both sides of the flat aluminum yarns have similar reflectances) the shiny aluminum yarns are visible principally on one side of the fabric and are principally covered by the warp yarns on the other side. Thus the fabric may have a construction in which there are floats of yarns spanning a plurality of crossing yarns, e.g. it may be a satin or sateen. The metallic yarns are preferably of the supported type (e.g. a 1 end combined Lurex yarn as described at pages 136-139 of Man-Made Textile Encyclopedia edited by J. J. Press, pub. 1959 by Textile Book Publishers Inc.). In one suitable fabric the metallic yarns are about 1/64 inch wide (i.e., about 0.4 mm), have a multifilament (e.g. 20 filament rayon) yarn entwined around them, and are woven about 50-60 per inch, and the warp yarns are of rayon, woven (at right angles to the weft) about 80 per inch, the weave pattern being a 4/1 sateen. The shiny side, on which the metallic yarns are visible, preferably forms the inner surface of the umbrella reflector; good results have also been obtained even when the duller side is used as the inside. The fabric need not be opaque; thus very good results have been obtained with a fabric which, like that just described, transmits some 20 to 50 percent of the incident light. The intense heat from the quartz-halogen lamp is carried away and dissipated over a large area by the metal yarns and by the passage of convection currents of air around the light source and through interstices of the fabric.
As previously described, the unit 11 may be secured at various positions along the length of the umbrella shaft. For maximum light efficiency there is an optimum position. This is found to be at a location at which the filament helix 85 (or 85a) of the light bulb, and the surface of the adjacent reflector 21 (or 21a), are well within the fabric enclosure, i.e., at a level (measured axially of said shaft) which is well inward of the level of the fabric-attaching loops, especially at a point at which said filament is located at about the focal point of the portion of the intermediate band 82 adjacent thereto. Thus, for the construction specifically described above, a particularly suitable position is one in which the distance from the filament to the closest surfaces of the fabric is about 91/2 inches (which is about one half the radius of curvature of said intermediate band). Bringing the unit 11 further into the enclosure gives a "harder" light (i.e., a light which casts more sharply defined and darker shadows) while moving it further away from the ring 61 makes the light softer. There is an indicator 86 on shaft 12 to show the optimum location for the clamp 32.
When an observer looks axially into the mouth of the umbrella specifically described above, say from a distance of about 10 feet from the lamps 18, 18a, with one lamp 18a lit, he sees (FIG. 1) a very brightly lit inner zone 88 extending from the apex of the fabric cover (in a direction towards the observer) about half the length of the ribs, surrounded by a less brightly lit (or shadowed) outer ring 89 on the balance of the reflector. In the brightly lit inner zone each of the panels has a large elongated very bright band 91 so that there are eight such separate bright bands visible. When both lamps are lit the effect is similar but instead of a single bright band in panel there are a pair of such bright bands or a broader bright band.
The device as described above gives light having a color temperature of about 3,200°K, suitable for indoor photography. It may also be simply adapted to give a color temperature of, say, about 5,500°K for use with daylight-type photographic film, by mounting a blue filter between the light source and the light reflecting fabric 69. This may be a sheet 96 (FIGS. 9 and 10) of blue plastic (e.g. nylon) film having secured thereto a hanger or clamp 97 for supporting it on the shaft 12. In one preferred form illustrated in FIGS. 9 and 10 the sheet 96 is rectangular, slightly larger (e.g. about 1 inch larger on each side) than the axially projected reflective area of the unit 11, and mounted a few inches (e.g. 3 inches) from the closest portions of unit 11. With this construction most of the light given off by the light source passes through the sheet 96 which absorbs the red wavelengths but a portion travels directly to the fabric 69. This enables one to get the light effect of a blue sky with bright sunlight, using a filter which ordinarily produces a light that is bluer than ordinary daylight. One use for this modification is in outdoor motion picture photography to make objects in the shadows more visible by using the umbrella light as a supplement to natural light.
Reference is made to my earlier U.S. Pat. No. 3,437,802, which describes characteristics of quartz halogen lamps, and to U.S. Pat. No. 3,294,962 relating to an umbrella type lighting apparatus employing certain halogen quartz lamps.
As can be seen in the drawings, in a preferred form of the invention the size, shape and position of the switch box 26 are such that it lies substantially entirely behind the reflectors 21, 21a and reflective bridging piece 42, and thus does not act to block or absorb a significant portion of the light travelling axially from the fabric covering toward the mouth of the umbrella. In the illustrated construction the face of bridging piece 42 has a length of about 31/4 inches and a width of about 2 inches, and the total area of reflectors 21, 21a and bridging piece 42 (measured as projected in a direction parallel to the axis of shaft 12) is in the neighborhood of 25 to 30 square inches, which is well below 10 percent and even below 5 percent of the area at the mouth of the umbrella (which is in the neighborhood of 700 to 800 square inches). It is within the broader scope of the invention, however, for the reflectors and bridging piece to cover a larger proportion of the area.
It is noted that the manufacturer's instructions accompanying General Electric DYH quartz halogen lamps specify "Do not direct beam at persons and materials from less than four feet." As indicated above, the distance from the lamp to the closest portions of the umbrella fabric is generally much less than two feet, usually less than about 1 foot and above about 1/2 foot. Yet the fabric does not become uncomfortably warm to the touch, much less reach the danger level, despite the flammability or charability of the fabric. Generally the fabric is of lighweight construction, having a weight well below 10, usually below about 5, ounces per square yard, such as about 3 to 4 ounces per square yard. In the preferred construction the reflectors 21,21a are substantially non-concentrating or non-condensing; they gather the light but do not focus it.
It is understood that the foregoing detailed description is given merely by way of illustration and that variations may be made therein without departing from the spirit of the invention.