I have some strange problem when setting pictures from Aperture 3 as wallpapers. For some reason they are not displayed in the full resolution Aperture 3 shows. For example a photo with a pixel size of 2048x1362 will be displayed much smaller (on my 1920x1080 iMac 21.5" screen). See attached screenshot. Any ideas as to what might cause this? Any help is appreciated. Thanks in advance.