Depth of Field Photography Basics Understanding aperture & depth of field requires a strong foundation in the basics of a camera lens, along with the vocabulary used to describe them, such as f-stop, focal length, focus range, and field of view. This section provides an overview of the basics. The following sections provide technical details allowing you to apply these concepts to your own photography. What is Aperture in Photography? The terms f-stop and aperture are often used interchangeably, this is incorrect. Aperture refers to aperture diameter, where light enters the front of the lens. F-stop is the ratio of lens focal length to aperture diameter. F-stop can be referred to as f-number or f-stop value. They are the same. F-stop is a dimensionless number, denoted by a hooked “ f ”, with an underlying number denoting the f-stop value. The hooked “f” is shorthand for f-stop, like the ”s.” after a shutter speed is short for seconds. f/2.8 and f/8 are two examples of common f-s