A brightline viewfinder is a type of camera viewfinder in which the subject is outlined by illuminated or bright frame lines. These lines often include parallax correction marks or indicate the fields of view for different focal lengths, helping photographers compose accurately and anticipate framing. Brightline viewfinders are commonly found in rangefinder and medium-format cameras, offering a clear, easy-to-see guide for precise image composition without relying on through-the-lens viewing.