Student Filmmakers - June 2008 - (Page 6) Cinematography Star Effects: Enliven Points of Light How Star Filters Work by Ira Tiffen Light is the lifeblood of imagery. Without it, imagery dies. Knowing how to bend light to your will is an important part of visual storytelling. What can we do when light sources themselves are actually in the scene? Fortunately, this provides even more opportunities for creative control. Let’s look at one category of effect that is particularly suited for getting the most dramatic effects from points of light in the scene. We refer to it as the ‘star’ effect. Star filters have been around a while. They can be viewed as gimmicky by some. And, if used improperly, that may be the case. However, being able to employ them judiciously can offer significant benefits to many situations. Star filters are excellent for transforming points of light in the scene into bright ‘starlike’ bursts blossoming out from each point. This has many uses, but before we discuss those, it will help us to better understand how they work. The traditional Star filter is a clear element, usually glass but not necessarily so, that has a series of fine lines ‘etched’ into one side. These lines act like tiny cylindrical lenses (envision a solid glass polished tube, cut in half lengthwise) that cause the point sources of light to spread out thin fingers of light perpendicular to the direction of the lines, from both sides. A filter with lines, which form a grid pattern across the filter’s surface, usually spaced 1, 2, 3, or 4mm apart, and running in only one direction, will create a single line of light running through a point of light passing through. This is seen as two ‘star lines’ emanating from opposite sides of the source, and aligned in a straight line. This is a ‘2-point’ Star filter; more commonly known as a ‘Streak’ filter, due to its appearance as a streak of light through the source. If the filter has more sets of parallel line grids running in different directions, there will be an additional set of ‘streaks’ for each direction there is a grid running. Typically, there are patterns to produce 4, 6, 8 and more points, in a symmetrical pattern, in addition to the Streak filter. The most commonly used filter is the 4pt. The spacing between lines in a millimeters, determines how many lines there are on the filter. The 1mm, being closely spaced, will have twice as many lines, for instance, as a 2mm filter, and will thus create a stronger star pattern. This also created the most flare. If you want overpowering stars, use a closer spacing; more finely crafted star points come from larger line spacing in the grid. The most popular spacing are the 2mm and 3mm. Some filters have asymmetrical patterns; they also involve grids having different line spacing in the same filter. These are designed to give a less ‘synthetic’ feel to the effect, more like a gleam or a glint than a star. Sparkles no filter Sparkles with Star filter grid, mentioned earlier as measured in studentfilmmakers June 2008
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