A mirror lens still forms a complete image because each point in the scene sends light through many parts of the lens, not just one matching area. Light from a subject point spreads across the lens opening at different angles, and the mirrors/lens elements redirect and refocus that light onto the sensor.

The central obstruction blocks some of the incoming light, but it does not block the center of the picture only. Instead, it reduces the pupil area used to form every part of the image. So the image remains whole, with reduced light-gathering and characteristic rendering rather than a central black disk.

The most visible effect is usually in out-of-focus areas: point highlights that would normally appear as soft discs become ring-shaped “donuts.” Many photographers find this distracting, though some use it creatively. In-focus image areas are generally not missing a center spot just because of the mirror.