have, and then the shadow will become much fainter. We can also include spatial averaging as
in Section 3.3.2, to reduce further the effect of the walking subject, as shown in Figure 3.22(h).
This gives spatiotemporal averaging. For this, we have not required any more images, but the
penalty paid for the better improvement in the estimate of the background is lack of detail. We
cannot see the numbers in the clock, because of the nature of spatial averaging. However, if we
form the background image by taking the median of the six images, a temporal median,weget
a much better estimate of the background, as shown in Figure 3.22(i). A lot of the image detail
is retained, while the walking subject disappears. In this case, for a sequence of images where
the target walks in front of a static background, the median is the most appropriate operator. If
we did not have a sequence, we could just average the single image with a large operator and
that could provide some estimate of the b