The snapshot advantage factor is easily derived from knowledge of the datacube dimensions and the measurement architecture. For example, for a datacube of dimensions , a whiskbroom (point scanning) system sees only 100 voxels of the datacube at any given time. If the remainder of the object is emitting light during this period, then all light emitted outside these 100 voxels is lost. The overall light collection efficiency from geometric considerations alone is thus the inverse of the number of elements in the scan—in this case . This value is cripplingly low for all but the most forgiving of experiments. For a pushbroom (line scanning) system, one sees a slice of the datacube at a given time, so the maximum full-cube efficiency value is . While many experiments can tolerate such a low efficiency, dynamic scenes prevent the longer integration times needed to overcome this poor light collection. Since the scan dimension in our example is one fifth that of the spatial dimensions, filtered cameras have the potential to provide a five-fold improvement in light collection ability. In practice, however, this is typically offset by light losses due to dead time between scan points or to low transmission in the spectral filters (see, for example, 13). Ignoring these losses, the geometric efficiency still remains low, at . These efficiency values given for scanning devices have been obtained by geometric considerations alone.