- An f-number is a measure of the light-gathering ability of an optical system such as a camera lens. It is calculated by dividing the system’s focal length by the diameter of the entrance pupil (“clear aperture”). The f-number is also known as the focal ratio, f-ratio, or f-stop, and it is key in determining the depth of field, diffraction, and exposure of a photograph. The f-number is dimensionless and is usually expressed using a lower-case hooked f with the format f/N, where N is the f-number.
- The Gorge Amphitheatre (Wikipedia)
The Gorge Amphitheatre, originally known as Champs de Brionne Music Theatre and commonly referred to as The Gorge, is an outdoor concert venue in Grant County, Washington, United States. It is situated near the Columbia River in Central Washington, nine miles (14 km) west of George. The venue is managed by Live Nation.