Photo Bubbling is an optical illusion that makes the viewer perceive the subject of a photo as being naked. This illusion is achieved by using circles (also called "bubbles") to expose only the bare skin of a subject, and hiding all the clothed areas. The viewer's brain then assumes that the areas they cannot see is also bare skin.

Example photo

This example shows the before and after of a photo once it has been bubbled using the Photo Bubbler.
More examples of photo bubbling can be seen on the blog.

Before

Clothed model before bubbling

After

Model after being bubbled