Wide Angle Lens Distortion and Fisheye Lenses

Wide Angle Lenses and Fisheye Lenses: An Introduction

Distortion is the change in magnification and angular resolution as a function of field angle in an image.

Optical Distortion, Wide Angle, and Fisheye are used when discussing lenses that provide a large field of view.

What is Wide Angle? What is Fisheye? Is there really a Difference?

Yes, there is a difference between a fisheye and a wide-angle lens. A definition from the Smith's Modern Optical Engineering, Fourth Edition, page 718, is: 

Fisheye: A lens with a field of view of 180° or more.

Therefore, a Fisheye Lens can be a Wide Angle Lens when an image sensor smaller than the image circle is used.

A Wide Angle Lens is not necessarily a Fisheye Lens.

GoPro's marketing team was stuck with "Fisheye" because the first product used a cropped Fisheye lens. The newer GoPros use Wide Angle lenses which are not Fisheye lenses.

So How Can a Fisheye Lens Be Wide Angle? But Not Vis-Versa?

Fisheye Lenses with 180°+ Field of View do not always provide 180° FoV if used with a smaller sensor.

For example, a Fisheye with Full Coverage can provide much smaller fields of view such as 160° Diagonal, where they act as a "Wide Angle" Lens.

The reason for this is the "Fisheye Fill Factor" which has six different general categories.

Wide Angle vs Fisheye Lens

Barrel Distortion as a Third Order Optical Aberration

Optical distortion is a third order transverse aberration. The simple explanation is that distortion is the change in magnification (angular resolution) versus image height.

Distortion is present in all fisheye lenses and most wide-angle lenses.

Additionally, distortion is a function of field angle, and usually increases as field increases.

Rule of Thumb 1: A lens with greater distortion has greater field of view than another lens which has the same Effective Focal Length.
Rule of Thumb 2: The smaller the field of view, the less apparent optical distortion is.

The distortion profile of a lens dramatically changes the field of view output from a camera system. In the below charts you can see that a 1.9mm lens can provide anywhere from 106° Field of View to 180°+ Field of View at 5.0mm image circle. 

Fisheye Distortion Projection Rectilinear Stereographic Equidistant Equisolid
Angular Resolution of Fisheye Lens Distortion

What is the Difference Between Perspective Distortion and Optical Distortion?

Optical distortion is a third order transverse aberration. The simple explanation is that distortion is the change in magnification (angular resolution) versus image height.

Distortion is present in all fisheye lenses and most wide-angle lenses.

Rule of Thumb 1: A lens with greater distortion has greater field of view than another lens which has the same Effective Focal Length.
Rule of Thumb 2: The smaller the field of view, the less apparent optical distortion is.

Why does Distortion Matter to Computer Vision?

Distortion changes the scale of objects at different parts of the field of view. Additionally, the scale changes both radially and tangentially, causing object deformation.

CNN-based methods should ideally be trained on data that has the distortion profile used by your embedded vision system. Otherwise, activations will occur in incorrect locations.

Distortion and Computer Vision

Pei, et. al. "Effects of Image Degradations to CNN-based Image Classification"

Distortion changes the scale radially and tangentially, causing line deformation.

Distortion and Computer Vision

Pei, et. al. "Effects of Image Degradations to CNN-based Image Classification"

Li, et.al. 2020, “ULSD: Unified Line Segment Detection across Pinhole, Fisheye, and Spherical Cameras”​ 

View Other Image Quality and Computer Vision Topics

What's Your Application? Our Board Lenses Cover the Spectrum.

Wide-Angle 3.6mm M12 Lens

CIL336-F1.9-M12A650

Wide-Angle 3.6mm M12 Lens

188°@6.6mm IP67 M12 Fisheye

CIL222-F2.0-M12A650

188°@6.6mm IP67 M12 Fisheye

185°@7.8mm Fisheye M12 Lens

CIL227-F2.5-M12ANIR

185°@7.8mm Fisheye M12 Lens

Does it Require an IP65+ Lens?

We offer IP65+ variants of many lenses. These are suitable for applications  exposed to the environment, without a window.

Mobile Robotics?

Find a low F# or low distortion lens to optimize your computer vision framerate.

Low Distortion 2.2mm M12 Lens

CIL023-F2.2-M12A650

Low Distortion 2.2mm M12 Lens

Wide-Angle 3.5mm M12 Lens

CIL335-F1.8-M12A660

Wide-Angle 3.5mm M12 Lens

Mid-Range 7.6mm M12 Lens

CIL080-F1.8-M12IR

Mid-Range 7.6mm M12 Lens

200°@5.7mm IP67 Fisheye M12 Lens

CIL217-F2.7-M12ANIR

200°@5.7mm IP67 Fisheye M12 Lens

Telephoto 35mm M12 Lens

CIL350-F2.4-M12A650

Telephoto 35mm M12 Lens

Telephoto 26mm M12 Lens

CIL260-F2.0-M12NIR

Telephoto 26mm M12 Lens

Surveillance?

Our low F#, high resolution lenses are suitable for 180° dome cameras, low light, and active IR illuminated scenes.

Consumer / AR+VR?

Our high resolution fisheye lenses will let you design 360° cameras and and stereographic lenses are equivalent to "GoPro" lenses.

226°@3.9mm Fisheye M12 Lens

CIL212-F2.2-M12A660

226°@3.9mm Fisheye M12 Lens

Low Distortion 2.6mm M12 Lens

CIL028-F2.3-M12A650

Low Distortion 2.6mm M12 Lens

GoPro 3.0mm M12 Lens

CIL331-F2.5-M12A660

GoPro 3.0mm M12 Lens

Low Distortion 1.8mm M12 Lens

CIL018-F2.8-M12A650

Low Distortion 1.8mm M12 Lens

Low Distortion 2.6mm M12 Lens

CIL028-F2.3-M12A650

Low Distortion 2.6mm M12 Lens

No Distortion 3.9mm M12 Lens

CIL039-F2.8-M12IR

No Distortion 3.9mm M12 Lens

Video Conferencing?

Our wide-angle, low distortion, high resolution M12 lenses result in optimal object deformation without post-processing.

Aerial Robotics?

Our light-weight, miniature lenses are ideal for collision avoidance, long-distance viewing, and end-customer viewing.

Small 2.1mm M12 Lens

CIL821-F2.4-M12B650

Small 2.1mm M12 Lens

Large Format 3.5mm M12 Lens

CIL334-F2.2-M12A660

Large Format 3.5mm M12 Lens

Wide-Angle 3.5mm M12 Lens

CIL335-F1.8-M12A660

Wide-Angle 3.5mm M12 Lens

Surveillance?

Our low F#, high resolution lenses are suitable for 180° dome cameras, low light, and active IR illuminated scenes.

Video Conferencing?

Our wide-angle, low distortion, high resolution M12 lenses result in optimal object deformation without post-processing.