Camera Lens Effective Focal Length Calculator (EFL Calculator)

Focal Length Calculator.webp__PID:b5ddb454-486a-4633-a5f9-5eab9cd96b87
A Camera Focal Length Calculator. This Calculates a Lens EFL for Cameras.

What is Effective Focal Length (EFL)?

The focal length of a lens is the distance from its principal plane to the sensor when the lens is focused at infinity. It sets how “zoomed-in” your camera is, much like resistor value sets current in a circuit. The focal length requirement for your camera is also dependent on the image sensor size.

Engineers often talk about effective focal length (EFL) because real lenses have multiple glass elements and principal planes that don’t sit at the mechanical mount. EFL gives you a single number that still predicts field of view (FoV) exactly. Think of it as the optical “equivalent resistance” of a lens stack.

Field of view shrinks as focal length grows and expands as the sensor gets larger. Horizontal, vertical, and diagonal FoV each use the matching sensor dimension. An online EFL calculator saves you from manual trigonometry: enter sensor width, desired FoV, and it solves for focal length in millimeters.

Most tools assume the lens is focused at infinity, which is valid for robotics and machine-vision ranges beyond a few metres. If you work at macro distances, refocus and recalculate because EFL shifts slightly with object distance.

Distortion Impacts the Calculation. Real-world design rarely stops at EFL. Wide-angle lenses introduce barrel distortion which changes the FoV and EFL calculation. Check datasheets for distortion plots and ensure BFL + shim thickness equals your sensor flange depth.When selecting a lens, start with your required FoV, plug it into the calculator, and pick the nearest catalog lens that covers your sensor format.

Read Our Camera Calculator & Optics Design Page, or Click below Use our Other Camera Calculators

Camera Field of View Calculator. FoV Calculator
Camera Depth of Field Calculator. DoF Calculator.
Camera Angle of View Calculator for Camera Lens Selection. AoV Calculator.

Here are a Few M12 Lenses. Search all 50+ Using Our M12 Lens Calculator

195°@5.2mm Fisheye Lens

CIL818-F2.0-M12A660

195°@5.2mm Fisheye Lens

Wide-Angle 4.8mm M12 Lens

CIL948-F2.0-M12B650

Wide-Angle 4.8mm M12 Lens

Wide-Angle 3.6mm M12 Lens

CIL336-F1.9-M12A650

Wide-Angle 3.6mm M12 Lens

Wide-Angle 2.8mm M12 Lens

CIL329-F2.0-M12A650

Wide-Angle 2.8mm M12 Lens

200°@2.9mm Fisheye M12 Lens

CIL208-F2.2-M12A650

200°@2.9mm Fisheye M12 Lens

We Also have Cost Effective 12MP+ C-Mount Lenses for Machine Vision and Factory Automation.

No Distortion 4.2mm M12 Lens
No Distortion 4.2mm M12 Lens
No Distortion 4.2mm M12 Lens
No Distortion 4.2mm M12 Lens
No Distortion 4.2mm M12 Lens
No Distortion 4.2mm M12 Lens
CIL042-F1.9-M12A650
No Distortion 4.2mm M12 Lens
$49.00
DSL210 DSL224 2mm S-Mount Lens IMX335 Framos
DSL210 DSL224 2mm S-Mount Lens IMX335 Framos
2mm M12 Lens IMX335 Framos Basler
2mm M12 Fisheye Lenses IMX335 Framos
CIL282-F1.8-M12B660
190°@6.8mm Fisheye M12 Lens
$49.00
Wide Angle M12 Lens Sunex
Wide Angle M12 Lens Sunex
Lensation Wide Angle M12 S Mount Lens
Edmund Optics Wide Angle Lens s-Mount
CIL332-F1.8-M12B660
Wide Angle 3.2mm M12 Lens
$39.00
Stereographic Fisheye Lens M12 S Mount Lens
Stereographic Fisheye Lens M12 S Mount Lens
Sunex Tailored Distortion M12 Fisheye Lens
Stereographic miniature fisheye S-Mount lens
CIL293-F2.2-M12A650
190°@5.4mm Stereographic Fisheye M12 Lens
$129.00
8mm Edmund Blue Series M12 Lens 58203 83-940
8mm Edmund Blue Series M12 Lens 58203 83-940
8mm S-Mount Lens
8mm M12 Lens allied Vision Basler
CIL382-F2.0-M12A650
Wide-Angle 7.8mm M12 Lens
$29.00
Molded Glass Aspheres M12 Lens Low Distortion
Molded Glass Aspheres M12 Lens Low Distortion
Molded Glass S-Mount
M12 Lenses Low Distoriton
CIL093-F2.4-M12ANIR
All Glass Low Distortion 2.8mm M12 Lens
$129.00

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

Mobile Robotics?

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

Factory Machine Vision?

Our cost-effective compact C-Mount lenses are designed for up to 1.1"~1.2" format global shutter sensors.

Intelligent Everywhere?

Our low distortion lenses with multiple F# can be used to optimize your depth of field.

Surveillance?

Our fisheye and IR Corrected lenses are suitable for doorbell cameras and active IR illuminated scenes.

Wide-Angle 4mm M12 Lens

CIL341-F2.0-M12A650

Wide-Angle 4mm M12 Lens

Wide-Angle 6.8mm M12 Lens

CIL368-F1.8-M12A650

Wide-Angle 6.8mm M12 Lens

200°@4.5mm Mini Fisheye M12 Lens

CIL914-F2.4-M12A650

200°@4.5mm Mini Fisheye M12 Lens

Exposed to the Elements?

Our IP67 and IP69K lenses are suitable for applications exposed to the environment.

Aerial Robotics?

Our tiny lenses are ideal for collision avoidance and object recognition.

IP67 12mm M12 Lens

CIL120-F2.4-M12A650

IP67 12mm M12 Lens

186°@5.2mm IR Corrected Fisheye M12 Lens

CIL239-F2.0-M12A650

186°@5.2mm IR Corrected Fisheye M12 Lens