Set View Type lets you switch between orthonormal and perspective viewing transformations. An image of the menu options is shown below:

View, Set View Type
The options in the View Type menu allow you to switch between the Perspective and Orthonormal transformations.
Icon Type Description
View, Perspective Perspective This view type uses the perspective viewing transformation. In a perspective transformation, the image will be rendered with a vanishing point so that distant parts of the image will appear smaller than close parts.
View, Orthonormal Orthonormal This view type uses the orthonormal viewing transformation. An orthonormal transformation does not scale the image based on distance. Orthonormal view type is recommended for best results when using the zoom box