The focal length calculator is a simple tool that facilitates the process of computing the magnification, focal length, and the angle of view.
Taking a picture of an object from a distance might be challenging - we'll help you find the right focal length to create an image that perfectly fits your cameras' sensor size. 📷
In the article below, we'll teach you how to find the focal length, discover the lens equation, and talk about a few essential principles of photography and the lens choice.
What's the focal length?
Focal length is one of the primary values of a photographic lens. Manufacturers usually give it in millimeters (mm).
Focal length describes the distance between the rear principal point and the sensor - in other words, it's the space starting from the center of the lens, to the point where the light rays converge in the focal point (to form a sharp picture on a surface of a digital sensor, or 35mm film).
|💡 Focal length can be determined only when the lens is focused at infinity.|
🖼️ Thanks to the focal length, we're able to calculate the angle of view - this variable informs us of the amount of the scene that will be captured. The wider the angle, the more of the scene can be transferred to a sensor, and be visible on the photograph. Thanks to the angle of view option, we don't really need an additional field of view calculator - we got everything ready!
🔍 Thanks to our lens focal length calculator, you may also find the magnification - it allows us to measure how the size of an object changes when transferred to photography.
Still hungry for knowledge? Try our other lens calculators:
How to use the focal length calculator?
Our lens equation calculator has a straightforward structure; fill in at least three fields in order to acquire results.
Typical image sizes:
- 3.6, 4.8, 5.8, 6.4, 8.8, 12.8 mm,
- or 1/4, 1/3, 1/2.5, 1/2, 2/3, 1 inch.
(Hey, if you're still not familiar with different units, try our length conversion tool 😉)
Object distance is measured from the lens's front principal plane to the object itself.
|💡 Remember, our calculators work both ways. Your result can simply become another query!|
The lens that makes objects appear small will have a small magnification - on the other hand, the lens that magnifies the picture will have a big magnification.
How to calculate focal length?
Finding focal length is an easy and very much needed ability; follow our simple guide to find all the details of these calculations!
The typical focal length formula looks as follows:
1/Focal length = 1/Image distance + 1/Object distance,
- Image distance and Object distance are given in mm.
And here's the transformed equation that we use:
Focal length = (Object distance / ((1 / Magnification) + 1)) * 1000,
- Object distance is given in mm; and
- Magnification does not have a unit.
In order to copy the lens magnification calculator, you'll need the following equation (take a closer look - it may also serve as an image distance formula!):
Magnification = Image size / Object size = -(Image distance / Object Distance),
- Object size - is the real size of an object, given in mm; and
- Image size - is the size of the camera's digital sensor or 35mm film, given in mm.
To calculate the angle of view, you need to use the most complex equation of them all:
Angle of view = (180/π) * 2 * aTan(Image size / (2 * Focal length * (Magnification + 1))),