Depends on how far away from the image you are, or how big it is. By taking the low frequency from one image, and the high frequency from another, you can get some interesting results. Take a look at this image, first sitting near the screen, then step away a couple of meters.
Open that image in a new tab, then hold down CTRL and scroll up/down to zoom in and out. When you zoom out to 25%, each of them switches from smiling to frowning or vice versa. The lady on the right is clearly smiling at 25% zoom. I had no idea that was possible.
http://cvcl.mit.edu/GroupFaceHybrid.jpg