Multiple-projector fulldome video systems rely on two or more video projectors edge-blended to create a seamless image that covers a hemispherical projection surface; splitting the entire image up into segments allows for higher-resolution imagery and projector placement that does not intrude on the viewing area underneath the dome. A disadvantage of multiple projection is the need to frequently adjust the alignment of projectors and the uneven aging of separate projectors leading to brightness differences between segments. Even minor performance differences between projectors can be obvious whan projecting a solid color across the entire scene.
Single-projector fulldome video systems use a single (or mixed) video source displayed through a single fisheye lens, typically located at or near the center of a hemispherical projection surface. A single projector has the benefit of avoiding edge blends (see below) between multiple projectors. A disadvantage of central projectors is the loss of the center of the dome for optimal viewing of the reconstructed perspective view provided by true hemispheric projection, a problem shared with traditional Planetarium projectors. High quality hemispheric projection lenses are very expensive and operate at the practical limits of optical performance needed for high resolution full dome coverage.
