The left column shows the image processed by a high-pass filter, while the right column uses a low-pass filter. When the two images are added together, we get the original image back, because all the frequency content has been included. This experiment confirms the linearity (additivity) of the spectrum.

HIGH-PASS FILTER CHANNEL		LOW-PASS FILTER CHANNEL
	Filter with different filters
	Rather different results
Add the two together and ....		... we are back where we started!