---
title: fStop
framework: modelio
role: symbol
role_heading: Instance Property
path: modelio/mdlcamera/fstop
---

# fStop

The relative aperture ratio of the camera’s simulated lens.

## Declaration

```swift
var fStop: Float { get set }
```

## Discussion

Discussion Relative aperture, also called f-stop or f-number, is a measure of the amount of light permitted through a lens to an imaging surface, commonly thought of as the “speed” of the lens. The f-stop is the ratio of the lens’s focalLength to the diameter of the entrance pupil. It controls the amount of light that reaches the sensor, as well as the size of out-of-focus parts of the image. The default relative aperture is is 5.6, simulating an f/5.6 lens.

## See Also

### Modeling a Physical Lens

- [barrelDistortion](modelio/mdlcamera/barreldistortion.md)
- [fisheyeDistortion](modelio/mdlcamera/fisheyedistortion.md)
- [opticalVignetting](modelio/mdlcamera/opticalvignetting.md)
- [chromaticAberration](modelio/mdlcamera/chromaticaberration.md)
- [focalLength](modelio/mdlcamera/focallength.md)
- [apertureBladeCount](modelio/mdlcamera/aperturebladecount.md)
- [bokehKernel(withSize:)](modelio/mdlcamera/bokehkernel(withsize:).md)
- [maximumCircleOfConfusion](modelio/mdlcamera/maximumcircleofconfusion.md)
- [focusDistance](modelio/mdlcamera/focusdistance.md)
- [shutterOpenInterval](modelio/mdlcamera/shutteropeninterval.md)