Jack Kennealy , Apr 25, 2001; 05:01 p.m.
David, I'm not sure where that comes from, but, without referring to my reference books, I'd call that filter simply one variation of a linear high-pass filter - which, to be complete, should also be divided by 179, I believe.
I believe that, strictly speaking, the unsharp mask process is not quite a simple linear process, and, therefore, can not be described by a single convolution kernel.
If I'm wrong, I'm sure someone will correct me! It's been a while since I buried myself in the mathematics of this! Embarrassing...