In optics, the term "stop" properly refers to the aperture itself, while the term "step" refers to a division of the exposure scale. Some authors, e.g., Davis (1999, 13), prefer the term "stop" because they refer to steps (e.g., on a step tablet) that are other than powers of 2. ISO standards generally use "step", while photographers normally use "stop". Davis, Phil. 1999. Beyond the Zone SystemArchived 2007-03-10 at the Wayback Machine, 4th ed. Boston: Focal Press. ISBN0-240-80343-4
In optics, the term "stop" properly refers to the aperture itself, while the term "step" refers to a division of the exposure scale. Some authors, e.g., Davis (1999, 13), prefer the term "stop" because they refer to steps (e.g., on a step tablet) that are other than powers of 2. ISO standards generally use "step", while photographers normally use "stop". Davis, Phil. 1999. Beyond the Zone SystemArchived 2007-03-10 at the Wayback Machine, 4th ed. Boston: Focal Press. ISBN0-240-80343-4