Focal length is a fundamental concept in photography that determines the magnification and angle of view of your lens.
Understanding Focal Length
- The focal length of a lens is the optical distance (usually measured in mm) from the point where the light meets inside the lens to the camera's sensor. This distance is a key factor in how large objects appear in your photo and how much of the scene is captured.
Focal Length and Angle of View
There's a direct relationship between a lens's focal length and its angle of view:
- Shorter focal lengths (like 18mm or 35mm) have a wider angle of view, allowing you to capture more of the scene.
- Longer focal lengths (such as 200mm, as mentioned in the reference) have a narrower angle of view. This means they zoom in on subjects, making them appear larger and bringing distant objects seemingly closer.
This principle is why different lenses are used for different purposes – wide-angle lenses for landscapes or architecture and telephoto lenses for wildlife or sports.
Beyond Optical Focal Length
It's important to distinguish optical focal length from digital zoom. While modern devices like smartphones allow you to "zoom in," this often doesn't change the optical focal length. Instead, it typically involves cropping the image sensor's output or using digital processing, which can affect image quality differently than using a lens with a true longer focal length.
Key Takeaways
- Focal length is an optical property of the lens.
- It's measured in millimeters (mm).
- It determines the angle of view and magnification.
- Longer focal lengths provide a narrower view and greater magnification.
- Digital zoom is not the same as changing the optical focal length.
