The processing techniques described in this chapter assume some preprocessing. A background image should be created as an average of a series of images collected just before the actual measurements. This background image should be subtracted from each image before any further processing is performed. The variance of the background image and the typical intensities of the light scattered from particles in the liquid should be used to determine a intensity threshold so that light scattered and reflected from the surface of the liquid (water or soap film) is below the threshold and light scattered from particles is above the threshold.
The differences between the flow in the Faraday experiment and in the soap film channel makes it necessary to use slightly different techniques for the two experiments.