Image Processing Reference
In-Depth Information
Figure 36-3 Comet trails.
Camera operators were trained to point the camera away from a bright point
source because this could permanently damage the camera tube. The consequence was
that you got comet trails (Figure 36-3) showing up whenever some stage lighting came
into view.
You might also see dark patches in images a few minutes later when the producer
switched back to the camera and the plumbicon either had not settled back to the normal
sensitivity across the whole surface or had been permanently damaged (Figure 36-4).
Modern professional CCD video cameras don't suffer from this, and it is rare to see
the problem other than in older analog footage that is being repurposed. It sometimes
shows up in cheaper cameras, which have longer exposure times, and it is also an issue
with digital still cameras under certain lighting conditions. You may see a strobing effect
on the comet trail due to the lighting being fed with AC electrical current.
This artifact is an integral part of the imaging process. You cannot easily remove it,
because it's a camera defect and therefore a part of the original recording.
Figure 36-4 Simulated camera-
tube burnout.
Search WWH ::

Custom Search