Cinematographer
Ich waehle die Blende primaer nach gewuenschter Schaerfentiefe und verfuegbarem Licht. f/1.4 fuer Portraets mit weichem Bokeh, f/5.6 fuer Gruppengespraeche.
Mathematical notation for expressing the relative light transmission of a lens. Calculated as focal length divided by aperture diameter.
F-Stop / F-Number
The F-stop is a standardized mathematical notation that indicates the relative aperture (light-gathering capability) of a lens. Despite the name, the F-stop is not the actual aperture opening, but a ratio between the focal length of the lens and the diameter of the aperture opening.
Mathematical Basis
The F-number is calculated using the formula:
F-Number = Focal Length / Aperture Diameter
Example 1: 50mm Focal Length / 25mm Diameter = f/2.0
Example 2: 85mm Focal Length / 42.5mm Diameter = f/2.0
Example 3: 35mm Focal Length / 17.5mm Diameter = f/2.0This means that a 50mm f/2.0 and an 85mm f/2.0 theoretically let through the same amount of light, even though the physical diameter is different.
The F-Stop Sequence
The standard aperture sequence follows a mathematical progression:
| Aperture | Light (relative) | Typical Application |
|---|---|---|
| f/1.4 | 16x | Extreme Low-Light, Bokeh |
| f/2.0 | 8x | Available Light, Portrait |
| f/2.8 | 4x | Standard Film Production |
| f/4.0 | 2x | Daylight, Documentary |
| f/5.6 | 1x | Reference Value |
| f/8.0 | 0.5x | Maximum Sharpness |
| f/11 | 0.25x | Landscape, Deep Focus |
| f/16 | 0.125x | Extreme Depth of Field |
F-Stop vs. T-Stop
The most important difference for filmmakers:
- F-Stop: Theoretical value based on geometry
- T-Stop: Measured light transmission including glass losses
A lens with f/2.0 might actually be T/2.3 if 15% of the light is absorbed by glass elements.
From the crafts
Perspectives
Director
Die Blendenwahl bestimmt, ob ich Zuschauer auf einen Charakter fokussiere oder die gesamte Szenerie gleichwertig zeige. Offene Blenden isolieren emotional.
Producer
Lichtstarke Objektive mit f/1.3-f/2.0 kosten das Drei- bis Fuenffache von f/2.8-Standardoptiken, sparen aber taeglich 2-3 Stunden Beleuchtungszeit.
More in the lexikon
Related terms
Test your knowledge
Quiz
1. Zu welchem Department gehört „Blendenzahl / F-Stop"?
2. Wie viele verschiedene Fachperspektiven bietet dieser Eintrag?