Focal Length Explained

What is Focal Length?

Focal length is a crucial camera specification that determines how wide or narrow a field of view your lens captures. It is measured in millimeters (mm) and is the distance between the optical center of the lens and the image sensor or film when the lens is focused at infinity.

Types of Focal Length Lenses

Lenses are generally classified into three focal length categories:

• Wide-angle lenses (less than 50mm): Capture a wide field of view, making them suitable for landscapes, architecture, and group shots.
• Normal lenses (around 50mm): Provide a natural perspective similar to the human eye, making them ideal for general photography.
• Telephoto lenses (more than 50mm): Narrow the field of view, making them suitable for portraits, wildlife photography, and close-up shots.

Choosing the Right Focal Length

Selecting the right focal length depends on your intended purpose:

• For wide shots, opt for wide-angle lenses (e.g., 16mm-35mm).
• For everyday photography, a normal lens (e.g., 50mm) is a versatile choice.
• For portraits and close-ups, a telephoto lens (e.g., 70mm-200mm) is suitable.

Impact of Focal Length on Depth of Field

Focal length also affects depth of field, the range of distances from the camera that appear sharp in the image:

• Wide-angle lenses: Create a deep depth of field, keeping most of the scene in focus.
• Normal lenses: Provide a moderate depth of field, balancing sharpness in the subject with some background blur.
• Telephoto lenses: Create a shallow depth of field, isolating the subject from a blurred background.

Focal Length in Different Camera Formats

Focal length also varies depending on the camera format, such as full-frame, APS-C, or Micro Four Thirds:

• A 50mm lens on a full-frame camera provides a normal field of view.
• On an APS-C camera, the same lens acts like a 75mm, effectively increasing the focal length.
• On a Micro Four Thirds camera, the 50mm lens behaves like a 100mm lens.

Conclusion

Focal length is a fundamental camera specification that plays a significant role in determining the field of view, depth of field, and overall image composition. Understanding focal length and its impact will empower you to make informed decisions when choosing lenses for different photographic applications.

Focal Length Explained