1. A collapsible background unit for use in association with a light source and a camera for photographing an object, the collapsible background unit comprising an enclosure with an illuminating wall that is translucent, the arrangement being such that when light from a light source is directed into the interior of the enclosure the illuminating wall transmits at least some of said light to the exterior of the enclosure, such that the illuminating wall, or an additional translucent component interposed between the illuminating wall and the object, constitutes a background for the object, wherein the collapsible background unit includes first and second panels, each panel comprising a sheet of flexible material mounted in a resilient frame and being adapted to maintain its shape during normal use, the first and second panels being connected by a web of flexible material that extends between the frames of the first and second panels, and the connecting web being held in tension by a plurality of removable support struts that extend between the panels, the support struts being situated externally of the connecting web.