The process generated some noise, but fortunately this is easy to clean up. The filtered photo was then subtracted from the unfiltered one, yielding the following image. A regular photograph was taken, followed by another which used a polarising filter to largely remove the specular light. Starting off with something simple, a teeshirt was soaked in water so that it would reflect specular light well. This project looked at replicating this technique and seeing how practical it is when taken outside a lab or studio environment and into ‘the wild’. The second image is then subtracted from the first to leave largely specular light. The method uses two photographs of the same scene, the first one is a regular photograph and the second is one with specular highlights removed by a polarising filter. Polarisation refers to the orientation of the light when represented as a wave, and it’s possible to filter out this light with a polarising filter. If the material is dielectric (eg glass or water) then this light will have a uniform polarisation. The method takes advantage of interesting property of light which is specularly reflected from certain materials. Graphics researcher Paul Debevec devised a method for isolating specular light in his Digital Emily project. The reflections from the lights in the photo below give a good example of specular highlights. These highlights give additional visual cues about the material and they also change as someone moves around the object, giving cues relating to its structure. For this reason, specular reflections in these materials are sometimes called ‘specular highlights’. Light being reflected from a material may have both specular and diffuse components, the specular part often occurring in a small bright area at a suitable angle relative to a light source.
Still water can give a good example of a specular reflection and matte paper a good example of a diffuse one. The light may be reflected from a surface either specularly, meaning in one direction, or diffusely, meaning in a multitude of directions. Light emanates from a source and is reflected from these structures to reach someone’s eye. Visual information about a space comes from the interaction between a light source and the structures in that space. This was part of a second year project looking into different aspects of light.
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