A Theory of Image Quality: The Image Quality Circle

©2004, IS&T—The Society for Imaging Science and Technology The twentieth century brought the development of television and digital imaging. Demonstration of a complete television system by Philo Farnsworth on September 7, 1927 ushered in the age of electronic imaging.4 Like the images in Lippershey’s and Galileo’s telescopes centuries earlier, live television images are transient. Photographic film was used to record images in the early days of television, before magnetic tape recording. In its day, the system for recording a television broadcast was perhaps the most complicated imaging system devised, comprising optics, photography and electronics. The launch of the Sputnik satellite by the Soviet Union on October 4, 1957 lit the fuse on the race into space, and imaging probes have always been a principal component of space exploration. The first probes imaged the moon; later they were sent to outer planets of the solar system. These probes ushered in the age of digital imaging with both terrestrial and space applications. Today digital imaging has progressed from expensive one-of-a-kind space applications to achieving widespread commercial importance, starting initially in diagnostic medical imaging and the prepress area of commercial printing. Digital imaging has been fully developed in the consumer, office and industrial sectors since the advent of the personal computer a little over 20 years ago. Looking at the history of imaging technology, we see that image quality has not been at the top of the list of design criteria during the initial phases of technology development. The imaging system first had to “work” and record an image. Only after achieving successful image recording does image quality become a high priority. The first image quality topic usually addressed by product developers is the rendering of tones that comprise the image, then the spatial structure or the image details. Finally, as an imaging technology develops, attention is focused on the color quality of the image.