"Both have a 2560 x 1600 pixel canvas to use the largest
commonly offered resolution, currently. Passepartout layers allow
to see how things will look when this space is cropped to conform
to other common aspect ratios.
"This simulates the effect the Style: Zoom setting in Appearance
Preferences: Background will have: the image is scaled up or down
such that it fills the screen without distorting it"