Image Processing Reference
This was the unfocused blurred edge you started with.
This is the perfect sharp edge you wanted.
This was what the edge enhancer did.
Figure 34-13 Sharpening-halo waveform.
Avoid applying any edge enhancement if possible. It leads to ringing effects where
the edge detail overshoots if it is not applied correctly.
A lot of edge enhancement tends to be applied when movie film is transferred to
video. This is necessary because a low-pass filter is applied to remove aliasing and flicker
artifacts, which sacrifices some detail that can be restored by using some edge enhance-
ment. Beware, however; often, far too much edge enhancement is added and a halo effect
around dark objects is created. This is very difficult to remove later on.
Cropping the Input Source
The next step is to crop the picture to include the desired part of the image. This is neces-
sary for several reasons:
Video monitors and TV sets are designed to over-scan.
Computer displays do not over-scan.
It is necessary to crop off edge-blanking areas.