What does the F-stop measure on a camera lens?

The F-stop measures the aperture setting on a camera lens, which is crucial in determining how much light enters the camera. The F-stop is represented by numbers such as f/2.8, f/4, f/5.6, etc. A lower F-stop number indicates a wider aperture that allows more light to reach the sensor, which can result in a brighter image and a shallower depth of field. Conversely, a higher F-stop number indicates a narrower aperture, allowing less light and producing a deeper field of focus.

Understanding the relationship between the F-stop, aperture, and exposure is fundamental for photographers and videographers, as it directly affects the visual outcome of the image. While shutter speed measures how long the camera's sensor is exposed to light and ISO sensitivity refers to the sensor's responsiveness to light, the F-stop is specifically related to the size of the lens opening and its impact on the image's exposure and quality. Focus distance pertains to how far away a subject is from the camera and does not relate to the F-stop measurement.