Blendenwerten

Blendenwert, also called Blendenzahl, is the aperture value used in photography to describe the size of the lens opening. It is defined as N = f / D, where f is the focal length of the lens and D is the diameter of the effective aperture. The Blendenwert is a dimensionless number, and a smaller value means a larger opening, allowing more light to reach the sensor; a larger value means a smaller opening and less light.

The Blendenwert has a direct impact on exposure and depth of field. For a given lens and distance to the subject, the light reaching the sensor is approximately proportional to 1/N^2. In practice, stops are used to measure exposure changes: moving from one Blendenwert to the next typically doubles or halves the light. Common Blendenwerte (f-numbers) follow a standard sequence such as f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22. Some lenses offer additional intermediate values.

Beyond exposure, the Blendenwert also controls depth of field and sharpness. Smaller Blendenwerte (larger openings) yield a shallower depth of field and more background blur, while larger Blendenwerte (smaller openings) increase the depth of field. Extremely small openings can introduce diffraction, reducing overall sharpness.

In usage, Blendenwerten are selected via the camera’s aperture control and are commonly referred to in terms of f-numbers. The concept is equivalent to the English terms “aperture value” or “f-number” and is central to exposure calculation and optical design across photography and videography.