Hi Jim, normally what I have seen referred to as a high boost filter is when you take an image and possibly amplify it, then subtract from the amplified image a blurred (lowpass filtered) version of the image.
It is an image sharpening technique.
High pass filtering is when you simply apply a highpass filter to your image. A filter like this one for example:
b = [ 0.2333 -0.4040 0.1083 0.0625 -0.4040 0.6998 -0.1875 -0.1083 0.1083 -0.1875 0.0502 0.0290 0.0625 -0.1083 0.0290 0.0167]; freqz(b)
the high boost filter amplifies the high frequency components and it keeps the low frequency components intact(almost).
it also enhances the edges and removes the blurred parts