Fig 1. The result of spatial filtering of the recorded signal in a single pixel.

The signal in an individual pixel for a single image sequence is very noisy but after spatial filtering the difference between a response and background can clearly be seen. Note that spatial smoothing is used to reveal temporal structure in the signal. The graphs are normalised to more clearly show the result and the filter radius is indicated in pixels. Left. A pixel with a strong response. The response is clearly revealed when a larger area is weighed together. Middle. A weaker signal can only been seen after substantial smoothing. Right. A pixel without a response. Spatial smoothing gradually approximates the bleaching function.