GB2425589A

GB2425589A - Adjustable connection ring for photographic softbox or lighting umbrella

Info

Publication number: GB2425589A
Application number: GB0508920A
Authority: GB
Inventors: Manh Han
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-04-30
Filing date: 2005-04-30
Publication date: 2006-11-01
Also published as: GB0508920D0

Abstract

An adjustable connection ring for attaching a diffuser to a light source comprises an outer frame which is permanently rotatably mounted on an inner ring. The outer frame may have sockets or hinged joints for supporting the ribs of the diffuser, in which case the outer frame forms the diffuser armature. Alternatively or additionally the outer frame may have a radially adjustable clamping means for attachment to a separate armature of the diffuser. The inner ring has one or preferably a plurality of radially adjustable arms which allow it to be attached to the body or barn door attachments of light sources of various shapes and sizes. The apparatus allows a diffuser to be mounted on any available light source and then freely rotated to the optimal position.

Description

Adjustable connection ring for photographic softbox or lighting umbrella

This invention relates to connection rings and similar devices for connecting light diffusers such as softboxes, lighting umbrellas and the like to a light source.

In this specification the term "diffuser" is taken to embrace any device which is mounted on or around a light source so as to modify the light emitted therefrom, whether by diffusion, reflection or otherwise. Such devices are often but not exclusively used for photographic, film and video lighting.

A diffuser may be formed as a rigid enclosure, but softboxes and lighting umbrellas are more common. A sofibox comprises a foldable fabric cover which is typically stretched over a framework of resilient ribs so as to define a large light emitting opening opposite the light source. The ribs are typically supported by a central frame or connection ring which defines a central opening for accommodating the light source. In use the frame or ring is releasably attached to the light source, or sometimes to a separate supporting stand, so that the emitted light passes through the central opening in the frame or ring and into the diffuser.

The interior surface of the softbox is more or less reflective and the light emitting opening may be covered with a translucent light diffusing panel or with a grid of light orienting slats sometimes called an "eggcrate". Where the ribs are formed to resemble those of an umbrella or parasol the device is termed a "lighting umbrella". Other types of softbox may be formed as translucent enclosures which entirely surround the light source.

Numerous types of light source (often referred to in the industry as "lighting instruments") such as strobes and floodlights are available from many different manufacturers, so it is desirable that a diffuser should be compatible with as many alternative lighting instruments as possible. There is little standardisation between manufacturers, and lighting instruments have a wide variety of body shapes and sizes and a variety of different arrangements for the attachment of a diffuser. Most lighting instruments have a generally circular or rectilinear rim surrounding the light emitting face of the light, and many are provided with spaced-apart projections permanently fixed to the rim for the attachment of flaps known as "barn doors" or other accessories.

US 5,651,602 discloses an elongate, box-shaped diffuser which is provided at one end with four L-shaped arms for mounting the diffuser on a light source. The longer portion of each arm is mounted on the diffuser body by means of thumbscrews so that its shorter end portion projects radially inwardly beyond the end of the diffuser body. The thumbscrews allow the inwardly projecting end portion of each arm to be fixed at a selected distance from the end of the diffuser body. The end portion of each arm is provided with a radially adjustable bracket assembly which is clamped in place with a second thumbscrew. The bracket assembly is then tightened with two further screws so as to engage the rim of the light source. This device makes it possible to attach the diffuser to any of a variety of different lighting instruments.

A known type of adjustable softbox connection ring is commercially available from Chimera Lighting of Boulder, Colorado, USA. In this device four hooked, radially adjustable arms are mounted on an octagonal frame which is provided with sockets for supporting the ribs of the softbox or lighting umbrella. Each arm is first adjusted to engage the rim or the barn door holders of the lighting instrument, and then fixed in position on the frame by means of a thumbscrew.

Fixed locating studs on the frame engage in accurately positioned holes on the arm which are marked to indicate the correct arm positions for known lighting instruments of various sizes. Like the arrangement of US 602 this device allows the diffuser to be attached to any of a variety of lighting instruments.

When a diffuser is coupled to a lighting instrument, the arrangement of the filament or tube of the light as well as any integral reflector, refractor or other lens may result in an uneven distribution of light over the internal surface of the diffuser, which in turn may be apparent in the pattern of light cast upon the subject of the photograph. The shape of the diffuser will also influence the pattern of illumination, while the supporting ribs of a softbox or umbrella can cast unwanted shadows or "ghost images" on the scene.

In order to ameliorate these effects, and to make best advantage of the spread of light cast for example by a rectangular sofibox, it is desirable to rotate the diffuser so as to optimally adjust the pattern of light which it casts on the scene. A problem with the known arrangements described above is that, while the adjustable arms or clamps may be loosened, adjusted and then re-tightened in a different position on the annular rim of a round lighting instrument, this procedure is fiddly and time consuming. On square lighting instruments and lighting instruments equipped with barn door holders, it is only possible to attach the arms in certain pre-defined positions. It is therefore difficult or impossible to rotate the diffuser to the optimal position.

An alternative arrangement for mounting a diffuser on a variety of different lighting instruments provides a variety of interchangeable connection rings or adaptors. Each adaptor is releasably mounted on the frame of the diffuser and is designed for connection to a particular size and pattern of lighting instrument.

For example, US 6,733,145 discloses a folding softbox having an umbrellastyle frame including a central frame or backplate supporting the ribs. A number of interchangeable adaptors are provided, each adaptor including an identical, circular outer flange which is designed to fit the backplate, and an inner collar of varying design which is attachable to a particular style of light source. A suitable adaptor is selected depending on the lighting instrument to be used, and rotatably secured to the backp late.

US 6,808,295 similarly provides a softbox comprising a fabric cover supported by four flexible ribs which in turn are attached to a generally annular frame. The frame is provided with four equally spaced grooved mounting blocks which together define a seat which receives the circular outer flange of one of a plurality of alternative adaptors. Each adaptor has a differently sized inner collar for attachment to a light source of a specified diameter, and an identical outer flange which is seated in the grooves of the mounting blocks. After assembly, the frame is able to rotate about the adaptor. One of the mounting blocks is equipped with a spring catch for removing and replacing the adaptor, and a screw for selectively locking the joint to prevent rotation.

The use of an adaptor with a round flange advantageously allows diffusers of this latter type to be rotated at will around the adaptor after it has been attached to the lighting instrument. However, since such adaptors are provided with flanges of various designs for attachment to different diffuser frames, and in order to ensure that a diffuser of this type can be used on location with whatever lighting instrument is available, it is necessary to carry a large number of different adaptors for each diffuser. The mechanism for attaching and releasing the adaptors from the diffuser frame can also be a point of weakness.

It is the object of the present invention to provide a device for attaching a diffuser to a lighting instrument which ameliorates or overcomes the above problems and provides increased convenience in use.

According to the present invention there is provided a support frame for mounting a diffuser on a light source, comprising a first frame element having first attachment means for attachment to the diffuser and a second frame element having second attachment means for attachment to the light source; characterised in that the first frame element is rotatably connected to the second frame element, and the second attachment means is radially adjustable for attachment to a variety of different light sources.

Preferably the first frame element is permanently connected to the second frame element, which is to say, connected in such a way that it is not detachable in normal use.

The invention thus provides a diffuser mounting which allows the diffuser to be attached to any of a wide variety of different lighting instruments and then freely rotated to adjust the light according to the subject, while dispensing with the need to carry a variety of interchangeable adaptor rings on location.

The invention thus allows a diffuser to be mounted on round lighting instruments having a variety of different diameters, as well as on nonround light sources such as square bodied lighting instruments of different dimensions, and on lighting instruments which have fixed barn door attachment points at spaced positions.

After attachment of the diffuser to the chosen light source the invention allows it to be freely rotated so as to optimally illuminate the scene. This allows the user to position the diffuser so as to compensate for any unevenness in the pattern of light produced by the chosen lighting instrument.

Further features and advantages of the invention will be apparent from the following embodiments which will now be described by way of example and without limitation to the scope of the invention, with reference to the accompanying drawings, in which: Fig. lA shows a first support frame in a front view, i.e. seen from the diffuser side; Fig. lB shows the first support frame in a rear view, i.e. seen from the light source side; Fig. 1C is a front view of the first support frame mounted on a light source with a softbox attached; Figs. 1D, IE and iF are cross sectional views taken respectively in the direction of the arrows at lines D - D, E - E and F - F of Fig. 1B, with the background detail omitted for clarity; Fig. 2 is a rear view of a second support frame; Fig. 2A is a cross sectional view taken in the direction of the arrows at line A - A of Fig. 2, with the background detail omitted for clarity; Fig. 3 is a rear view of a third support frame; Fig. 4 is a front view of a fourth support frame; Fig. 5 is a rear view of a fifth support frame; and Fig. 5A is a cross sectional view taken in the direction of the arrows at line A - A of Fig. 5, with the background detail omitted for clarity.

Corresponding parts in each embodiment are indicated by the same reference numerals.

Referring to Figs. 1A - iF a first support frame comprises a first, outer frame element 1 and a second, inner frame element 2 which defines a central aperture for accommodating the lighting instrument. in the embodiment shown the outer frame 1 is simply formed as a flat aluminium ring with a circular inner margin and an octagonal outer margin, although other shapes are of course possible; for additional stiffness a rim or the like may be provided. The inner frame element 2 is similarly formed as a simple, flat aluminium ring and is rotatably secured to the outer frame I by means of bearings 3. Conveniently, each bearing comprises a pair of flat aluminium plates, best shown in Fig. 1E, which are secured for example by welding, riveting or screwing, one on each side of the outer frame 1 so that they overlap the inner ring 2 as shown. The inner ring 2 is thus permanently secured to the outer frame 1 but is free to rotate within it between the bearing plates 3, so that the outer and inner frame elements 1 and 2 form a permanent rotating joint. Other bearing means are of course possible.

If desired, the inner ring 2 can be releasably attached to the outer frame 1, for example by arranging for some of the bearing plates 3 to be easily removable.

Preferably however the inner ring is permanently rotatably mounted on the outer frame for robustness and so that there is no possibility of the two parts becoming separated and mislaid amongst the numerous accessories in the photographic studio.

As best seen in Figs. 1C and iF the outer frame 1 is provided with rib mounting blocks 4, for example moulded integrally with the outer frame 1 or alternatively welded to it, each block having a socket 5 which in use receives the inner end of one of the ribs 6 of the softbox 7. The softbox fabric 8 is stretched over the ribs 6 to define a large light emitting opening 9 opposite the support frame 1, 2. In the example shown the outer frame 1 is octagonal and has four sockets 5, so that it supports the four ribs of a square softbox. It will be appreciated that other shapes and other numbers of sockets might equally well be provided; for example, the octagonal outer frame shown might alternatively be provided with eight, equally spaced sockets to receive the eight ribs of an octagonal lighting umbrella.

The inner ring 2 is provided with attachment means for attaching it to the light source. In the example shown the attachment means comprises four radially adjustable arms 10, each arm having a light source engaging element 11 at its innermost end. In the example shown each light source engaging element is simply formed as a hooked portion 11, best shown in Fig. 1D, which can be engaged with the barn door holders of a round or rectilinear lighting instrument or alternatively with the rim of the body of the lighting instrument.

It will be appreciated however that each light source engaging element might alternatively comprise any other suitable attachment device, such as a spring loaded or thumbscrew-operated clamp, a magnetic clamp, a hookand-loop ("Velcro" (RTM)) pad, or any other suitable means for directly or indirectly attaching the support frame 1, 2 to the light source. It is also possible to provide only one light source engaging element, such as for example a single adjustable arm, rather than a plurality of equally spaced elements as shown.

In each case however the light source attachment means is radially adjustable, by which is meant that the attachment means is adjustable in a direction generally towards or away from the axial centre of the support frame 1, 2 so as to engage round light sources of greater or lesser diameter or non-round light sources of varying dimensions. Means may additionally be provided for adjusting the or each of the attachment means in other directions, such as circumferentially around the inner margin of the inner ring 2, or axially along the central axis of the support frame.

In the example shown, each arm 10 is provided with a slot 12 through which a thumbscrew 13 extends to engage a threaded bore in the inner ring 2. Each arm 10 can be slid radially in the direction of arrow G until its hooked end portion 11 engages the rim 16 of the light source 17 as shown in Fig. I C; the thumbscrew 13 is then tightened so that its collar 14 bears against a pressure pad 15 which clamps the arm 10 in position against the inner ring 2. The inner ring 2 is thus secured to the light source 17, allowing the outer frame 1 and diffuser 7 to be freely rotated around the inner ring 2 and the light source. By releasing the arms 10 the diffuser 7 may be removed from the light source 17 together with the support frame 1, 2 and re-attached for example to the barn door holders or to the square or rectangular rim of a different light source.

The range of radial adjustment of the light source attachment means is not necessarily limited by the diameter of the support frame 1, 2.

Referring to Figs. 2 and 2A, in a second embodiment the radially adjustable arms 10' are axially spaced apart from the inner ring 2 by means of support blocks 21 so that they clear the bearing plates 3 as the outer frame 1 is rotated. This allows the arms 10' to be slid back as shown until they project outwardly beyond the outer frame I, permitting a greater range of radial adjustment than in the first embodiment.

Each support block 21 is fixed to the inner ring 2 and has a rib 22 on its upper surface which extends upwardly into the slot 12 in the arm 10' so that the arm is constrained to move along the direction of the rib. In place of the thumbscrews 13 of the first embodiment, spring catches are provided for releasably securing the arms 10' in position.

A stud 23 with a flat head 24 is fixed in the centre of each rib 22, and a spring 25 is held in compression beneath the flat head 24 around the stud 23. The base of the spring abuts a flat plate 26, 26' which is free to rotate about the stud 23 and which has a pair of upwardly extending wings 27, 27'. Beneath the wings the lower surface of the plate 26, 26' is provided at its outer margin with two diametrically opposed downwardly projecting portions, which cannot be seen in the drawings, with bevelled edges.

In the view as shown, plates and wings 26, 27 have been rotated a quarter turn around their respective studs 23 so that the wings 27 and the downward projections of each plate 26 are aligned with the ribs 22 and slots 12. In this position the downward projections of each plate 26 are in abutment with the rib 22 of the respective support block 21. The spring 25 is thus held in compression between the head 24 of the stud and the plate 26 and support block 21, and the arm 10' is free to move. Conveniently, additional grip portions (not shown) may be provided at the outward ends of the arms 10' so that the user can more easily adjust them.

Plates and wings 26', 27' have been rotated a further quarter turn so that the wings 27' and downward projections of each plate 26' lie transverse to the respective rib 22 and slot 12. In this position the bevelled downward projections have ridden up onto the upper surface of the arm 10' so that the arm is now clamped to the upper surface of the support block 21 by the spring 25 and plate 26'. In order to ensure a more positive clamping action the abutting surfaces of the arm 10' and support block 21 may be serrated. Each arm 10' may be provided with an etched scale or the like to indicate the correct position of the arm for use with various sizes of lighting instrument.

Referring to Fig. 3, in a third embodiment each light source engaging element 11 is pivotably mounted at the first ends of two articulated arms 18, 19. One arm 18 is pivotably fastened at its second end 18' to the inner ring 2 while the second end 19' of the other arm 19 is pivoted on a mounting with a thumbscrew 13 which in turn slides along a slot 20 in the inner ring 2. Each slot 20 is curved as shown along a substantially circumferential line so that as the mounting is moved along the slot the hooked engaging element 11 moves in a substantially radial direction to engage the light source; the mounting is then secured in position by tightening the thumbscrew.

In a development (not shown), the thumbscrews 13 are replaced by pivotal connections which are engaged in short radial slots in a separate adjustment ring.

The adjustment ring is rotated to simultaneously adjust all four engaging elements 11; a single thumbscrew is provided for locking the adjustment ring in position against the inner ring 2.

Alternatively, each engaging element 11 may be mounted on a single arm which is pivoted at one end on the inner ring 2. In a still further modification, each engaging element can be mounted on a single arm which is pivotably and slidably engaged in a slot 20 in the inner ring. This for example would allow each engaging element to be adjusted in a circumferential direction around the inner ring so as to engage a light source at any angle and at any position around its rim.

In yet further embodiments the thumbscrews or spring catches for adjusting and securing the second attachment means may be replaced with other suitable catches; for example, short levers may be employed which are pivoted on the inner ring 2 and are provided at one end with an eccentric cam or the like which pressingly engages the arm.

It will be evident to those skilled in the art that many further adaptations may be made to the second attachment means within the scope of the invention.

Turning now to the first attachment means, it will equally be appreciated that the invention is not limited by the form of the attachment means for the diffuser. In the embodiments thus far described, the diffuser ribs are mounted in sockets 5 on the outer frame 1 so that the outer frame I forms the central supporting frame of the diffuser.

Referring to Fig. 4, in a fourth embodiment the second attachment means are formed generally as shown in Figs. 1- iF, but in place of the first attachment means 4, 5 the outer frame 1 is provided with a plurality of articulated rib mountings 40, 40'. The form of these rib mountings is shown in detail in the applicant's co-pending patent application no. GB 0327073.3, but in brief each mounting comprises a base portion 41 which is fixed to the outer frame 1, and a moveable portion 42 which is hinged to the base portion 41. The moveable portion 42 is adjustable between a deployed position as shown at 40 and a folded position as shown at 40', and is locked in the deployed position by means of a sprung catch 43. Desirably, each rib 6' of the softbox or lighting umbrella is permanently secured in a moveable portion 42 so that the support frame 1, 2 forms a permanent part of the umbrella; the fabric cover (not shown) remains in position when the rib mountings are folded for transport. Like the other embodiments the support frame 1, 2 defines a central aperture 44 which accommodates the light source; the inner ring 2 is clamped to the light source by means of the radially adjustable arms 10, after which the umbrella and the outer frame 1 are freely rotatable around the light source.

Referring to Figs. 5 and 5A, in a fifth embodiment the outer and inner frame elements 1, 2 and the second attachment means 10' are similar to those of the second embodiment, although the second attachment means 10' are here provided with thumbscrews 13 in place of spring catches. The first attachment means are also similar in that rib mounting blocks 4' and sockets 5 are provided, so that if required each rib of the diffuser can be mounted in a socket 5; the outer frame 1 then functions as the central supporting frame of the diffuser as it does in the second embodiment.

Unlike the previous embodiments however, the fifth embodiment allows a diffuser with an integral central supporting frame or armature, which often takes the form of a ring and supports the ribs of the diffuser, to be mounted on the outer frame 1. For this purpose each block 4' is provided with a radially adjustable frame mounting element 50 which is adapted to engage the separate central frame or armature of the diffuser. The frame mounting elements 50 are conveniently formed as radially adjustable arms 51 with central slots 52 through each of which a thumbscrew 13' extends to engage a threaded bore in the mounting block 4'. The central frame or armature of the diffuser is conveniently engaged by a hooked end portion 53 of each arm 51; in the example shown the end portion 53 includes both outwardly and inwardly facing slots 54, 55 which are enageable respectively with either an inwardly or an outwardly facing annular rim of the softbox armature.

The arm 51 is clamped in place by tightening the thumbscrew 13'.

Various adaptations, such as those described above with reference to the second attachment means, may also be applied to the frame mounting elements. For example, the hooked end portions 53 may be replaced by thumbscrew clamps or other suitable clamping means for engaging the armature of the diffuser, and a single adjustable frame mounting element (for example, a single adjustable arm or a single, axially projecting clamping element) may be provided in place of the four radial arms 51 as shown. Spring catches or the like may also be used in place of the thumbscrews 13'. The more conventional rib mounting blocks 4' may also be omitted, and the adjustable arms 51 mounted directly on the outer frame 1.

It will be appreciated that the support frame 1, 2 may be formed from any suitable metal, plastics or other materials, and may take forms other than those shown; for example, the inner margin of the inner ring 2 may be non-circular, and various asymmetrical arrangements of the first or second attachment means may be preferred for certain applications. The invention is accordingly not limited to the embodiments shown, and those skilled in the art will readily conceive of many other adaptations within the scope of the appended claims.

In summary, embodiments provide an adjustable connection ring for attaching a diffuser to a light source and comprising an outer frame which is permanently rotatably mounted on an inner ring. The outer frame may have sockets or hinged joints for supporting the ribs of the diffuser, in which case the outer frame forms the diffuser armature. Alternatively or additionally the outer frame may have a radially adjustable clamping means for attachment to a separate armature of the diffuser. The inner ring may have one or preferably a plurality of radially adjustable arms which allow it to be attached to the body or barn door attachments of light sources of various shapes and sizes. The apparatus allows a diffuser to be mounted on any available light source and then freely rotated to the optimal position.

Claims

Claims 1. A support frame for mounting a diffuser on a light source,

comprising a first frame element having first attachment means for attachment to the diffuser and a second frame element having second attachment means for attachment to the light source; characterised in that the first frame element is rotatably connected to the second frame element, and the second attachment means is radially adjustable for attachment to a variety of different light sources.
2. A support frame according to claim 1, characterised in that the first frame element is permanently connected to the second frame element.
3. A support frame according to claim 1 or claim 2, characterised in that the second attachment means comprises a plurality of radially adjustable light source engaging elements, together with means for securing each element in a selected position relative to the second frame element.
4. A support frame according to any of claims 1 - 3, characterised in that the first attachment means includes a plurality of rib mounting elements, each being adapted to receive a supporting rib of the diffuser.
5. A support frame according to any of claims 1 - 4, characterised in that the first attachment means includes at least one adjustable frame mounting element, the frame mounting element being adapted to receive a supporting frame or armature of the diffuser.
6. A support frame substantially as described herein with reference to the accompanying drawings.