Enter the actual focal length of the lens and the crop factor of the camera into the calculator to determine the effective focal length.
Focal Length Multiplier Formula
The following formula is used to calculate the effective focal length of a lens when used on a camera with a crop sensor.
EFL = AFL * CF
Variables:
- EFL is the effective focal length (mm)
- AFL is the actual focal length of the lens (mm)
- CF is the crop factor of the camera
To calculate the effective focal length, multiply the actual focal length of the lens by the crop factor of the camera.
What is Focal Length Multiplier?
The focal length multiplier, also known as the crop factor, is a number that represents the ratio of the sensor size of a digital camera to a 35mm film frame. This factor is used to calculate the effective focal length of a lens when it is mounted on a camera with a sensor size different from that of a full-frame camera. The effective focal length gives photographers an idea of the field of view they will get with a particular lens on a crop sensor camera compared to a full-frame camera.
How to Calculate Effective Focal Length?
The following steps outline how to calculate the Effective Focal Length.
- First, determine the actual focal length of the lens (AFL) in millimeters.
- Next, determine the crop factor (CF) of the camera.
- Next, gather the formula from above = EFL = AFL * CF.
- Finally, calculate the Effective Focal Length (EFL) in millimeters.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
actual focal length of the lens (AFL) = 50 mm
crop factor of the camera (CF) = 1.5
