title: The term magnification.
abstract: Many types of magnification described by different authors have dissimilar meanings. Basic principles of magnification such as relative size magnification, relative distance magnification and angular magnification used commonly in low vision are clarified in this paper. The three frequently-used terms of magnification, including apparent magnification, two relative magnification formulae, namely, M = F/4 and M = F/2.5, and iso-accommodative magnification are described. The concepts of equivalent viewing power (EVP) and equivalent viewing distance (EVD) are reviewed as an alternative means of specifying magnifying power. They represent an intrinsic property of an optical system that corresponds to the resolution afforded by the system in terms of dioptric power.