Bandpass filtering limitations. That such limits can be too narrow is exemplified by analysis of Drosophila's eclosion rhythmicity. Number of flies emerging are given on the ordinates, plotted vs. time. (a) Raw eclosion data from a wild-type culture monitored in DD. (b) Result of filtering the data in (a) with a bandpass set between 4–40 hours, such that only periodicities with values in this timespan survive application of the filter. (c) Result of filtering with bandpass set between 18–28 hours; such that, when the window of excluded frequencies is small enough, the data take on an artificial appearance. The clarity achieved with wider limits is replaced by a loss of potentially useful detail, or, worse, by distortion (see text).