**Aperture Calculator**

Aperture |
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Focal Length |
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fstop value |
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### Definition

The aperture of a lens is an opening through which light enters. Logically the larger the size of the aperture the more light will enter

In lenses, aperture is expressed in f-numbers (for example f/5.6). These f-numbers that are known as **“f-stops”** are a way of describing the size of the aperture. A smaller f-stop means a larger aperture, while a larger f-stop means a smaller aperture

To calculate the size of the aperture at a given fstop, we divide the focal length of the lens by the fstop number

The aperture of a 40mm lens at f/8 will be a circle with diameter of 40/8 = 5mm

The aperture of a 24mm lens at f/8 will be a circle with diameter of 24/8 = 3mm

**Note:**the light coming in at a given fstop is constant for all lenses of different focal length. Here is the explanation:

- The size of aperture at 24mm will be a circle with diameter of 3mm at f/8
- The size of aperture at 40mm will be a circle with diameter of 5mm at f/8

The lens at 40mm is longer than the lens at 24mm. Light falls in intensity over the distance it travels. So the light at the end of a longer lens is less intense than at the end of a shorter lens. Hence, for a 40mm lens, if the size of the aperture is larger as compared to the 24mm lens, the amount of light coming in will be the same

## Formula

To calculate the size of the aperture at a given fstop, we divide the focal length of the lens by the fstop number.

Aperture size_{(m)} = Focal length_{(m)} / f-stop number

**For Example:**

What is the size of aperture of a 40mm lens at fstop f/8?

**Sol. :**

Aperture size_{(m)} = Focal length_{(m)} / f-stop number

Aperture size = 40_{(mm)} / 8

Aperture size = 5_{(mm)} = 0.005_{(m)}

## Units

S.I unit of aperture is meter.