Diffusion filters are used in film, theatre and photography in order to change the characteristics of light from a light source or for aiming light. So it is that the light rays, for example, from a flood light can be spread; that is, they can be directed towards the sides to make that area brighter. In addition, diffuse light lessens the contrast that results from shadows and therefore accentuates the importance of the colour of a motif in the composition of a picture. In portrait photography, facial lines become less prominent (“beauty-light”) and in object photography it prevents harsh light from shining at the point of reflecting edges and eliminates deep, dark shadows. Like Rosco´s other ROSCO E-COLOUR FILTER FILM, SHEET, this heat resistant diffusion filter film is also suitable for use in lighting constructions and for encasing fluorescent tubes. The films can be easily cut with a blade or a scissors; gluing work can be done with adhesive tapes like, for example, SCOTCH MAGIC TAPE because it is heat resistant up to 150 °C.
The diffusion filter films that we have on offer are distinguished by the following attributes:
- White Frost, which is the most light transmitting of the three, lightly diffuses light from a specific light source and slightly reduces the amount of contrast.
- Atlantic Frost has moderate to medium light diffusion attributes and moderately reduces the amount of contrast. The light source is perceived as a somewhat brighter area.
- Heavy Frost, which is a very dense film, diffuses light to a great extent and produces an harmonious field of light which is soft and without shadows. Contrasts are greatly reduced.
Attributes: A clear statement concerning the colour of light is always difficult because light exists in conjunction with heat. Not every plastic film is able to withstand the heat produced by certain bulbs. Rosco E-Colour filter films were developed for use in theatre and film work and are therefore capable of colouring a beam of light produced by a powerful spotlight. Exposing the E-Colour filter films to long term UV illumination can produce a mild bleaching of the film.
In order to get an impression of the colour that will be produced using a particular film, the chosen light source should be shined through the relevant colour from the colour samples onto a surface. Just holding the film in front of your eyes and looking into the light will usually give a false impression.
Applications: When constructing a lamp a few points should be observed: the heat that a colour filter must withstand is not just dependent on its separation distance from an incandescent or halogen bulb. Much more important is the ventilation that the lamp allows. In the same way that the classic writing table lamp has a reflector with holes on its top side, a self-made lamp should be so constructed that the rising heat from the light source has an escape route. In this way the lamp produces, as if on its own, a cooling stream of air. A further issue concerning heat: the heat produced by a spotlight with a reflector is usually greater than that from one with a system of lenses because the reflector, in contrast to lenses, also tends to gather heat.
One easy way to make a lamp is to simply wrap colour filter film around a fluorescent tube. The temperature of a fluorescent tube is much lower than that of other illuminants so it is OK to just directly wrap the film around the tube. In this case, as also in the case of constructing any lamp with an incandescent or halogen bulb, the best agent for holding the film in place is SCOTCH MAGIC TAPE because it can withstand heat up to 150° C.
Treatment: Colour filter films are very thin which means they can be easily cut using a BLADE or SHEARS. This thinness and lack of strength is a disadvantage when the planned construction requires an inherent stability. This problem can be solved by using perforated sheets, wire mesh or expanded metal as a carrier material allowing for as much open area as possible (ao). Because of high resistance to heat, POLYCARBONATE or POLYPROPYLENE panels can also be used as long as enough ventilation is provided for in the lamp. Colour filter films can be attached to one another or to other materials with heat-resistant ADHESIVE TAPES, rivets or clamps. Please take into account the different expansion rates for any materials used in a construction that will be exposed to extreme fluctuations of heat. You should resist, for example, gluing a large area of metal with filter film because the resulting stress will quickly fatigue the adherence.