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tags:
- "⭐topic/⚙️hardware/\U0001F4F7camera"
---
# aperture   
   
The aperture is the opening that lets light into a camera. Aperture size is directly proportional to the [depth of field](../../notes/camera/depth%20of%20field.md) and exposure of photos. The size of the aperture is often measured in [stops](../../notes/camera/exposure%20stops.md), specifically *f-stops*, known as the *f-number*. Aperture stops are inverse, so a larger f-number results in a smaller entrance pupil, while a small f-number describes a wide open aperture.   
   
![](../../assets/Aperture%20terminology%20and%20scales.png)   
   
[Wikipedia](https://en.wikipedia.org/wiki/F-number):   
> The f-number N is given by:   
> > ${\displaystyle N={\frac {f}{D}}}$   
>    
> where $f$ is the [focal length](https://en.wikipedia.org/wiki/Focal_length), and $D$ is the diameter of the entrance pupil (_effective aperture_). It is customary to write f-numbers preceded by "f/", which forms a mathematical expression of the entrance pupil's diameter in terms of $f$ and $N$. For example, if a [lens's](https://en.wikipedia.org/wiki/Lens_(optics)) focal length were 10 mm and its entrance pupil's diameter were 5 mm, the f-number would be 2. This would be expressed as "f/2" in a lens system. The aperture diameter would be equal to $f/2$.