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The "f/" in aperture settings literally stands for "focal length divided by ...". e.g, an f/2 aperture on a 50mm lens has a diameter of 25mm. One aperture stop
by thequux 5y ago
The "f/" in aperture settings literally stands for "focal length divided by ...". e.g, an f/2 aperture on a 50mm lens has a diameter of 25mm.
One aperture stop corresponds to a scaling factor of sqrt(2), because the area of the aperture scales with the square of the diameter, and halving the area results in half the light (and 1/1.414... of the aperture diameter)
- roelschroeven 5y agoMore specifically the f/ number relates to the size of the entrance pupil (the optical image of the physical aperture stop, as seen through the front of the lens) rather than the size of the physical aperture. Depending on the construction of the lens and where in the lens the aperture is located, the two can differ quite a lot.