The Apply Lens filter simulates a fish eye lens and provides user controlable refraction.
Apply Lens Settings
There are three available options.
Keep Original Surroundings: This radio selection will leave the original image as the background and place the refracted image above it.
Set Surroundings to Background Color: This option will remove the original image, replacing it with a fill of the current background color. The refracted image will be placed above this color.
Lens Refraction Index: This setting dictates the amount of refraction that will be used for the filter. Higher settings will result in a less recognizable image.