The formula to calculate Focal Ratio (FR) is:
\[ FR = \frac{FL}{A} \]
Where:
The Focal Ratio, often referred to as the f-number or f-stop, is a dimensionless number that describes the ratio of the focal length of a lens or mirror to the diameter of the aperture. It is an important parameter in photography and optics, affecting the depth of field and the brightness of the image. A lower focal ratio indicates a wider aperture, allowing more light to enter and resulting in a shallower depth of field.
Let's consider an example:
Using the formula to calculate Focal Ratio:
\[ FR = \frac{200}{50} = 4 \]
This means that the Focal Ratio (FR) is 4.