35 mm equivalent focal length

Explanation of the 35 mm equivalent focal length in photography

35 mm Equivalent Focal Length

The 35 mm equivalent focal length is a concept used in photography to provide a common reference point for comparing the field of view of different camera and lens combinations. This equivalence is based on the 35 mm film format, which has been a standard in photography for many years.

Background

The 35 mm film format, also known as full-frame in digital photography, has a frame size of 36 mm by 24 mm. This format became a standard due to its widespread use in film cameras and its adoption in DSLR and mirrorless camera systems.

Concept

The 35 mm equivalent focal length is calculated to provide a consistent way to describe the field of view of a lens when used on different sensor sizes. This is important because the crop factor of a camera's sensor affects the field of view. For example, a lens with a focal length of 50 mm on a full-frame camera will have a different field of view than the same lens on a camera with an APS-C sensor.

Calculation

To calculate the 35 mm equivalent focal length, you multiply the actual focal length of the lens by the crop factor of the camera's sensor. The crop factor is the ratio of the diagonal of the 35 mm film format to the diagonal of the camera's sensor. For example, an APS-C sensor typically has a crop factor of 1.5 or 1.6, depending on the manufacturer.

Importance

Understanding the 35 mm equivalent focal length is crucial for photographers who want to achieve a specific field of view or composition in their images. It allows photographers to make informed decisions when selecting lenses for different camera systems.

Related Pages

• Crop factor
• Full-frame digital SLR
• APS-C
• Field of view
• Digital photography

Gallery

• 

  Comparison of full-frame and APS-C sensor sizes

• 

  Comparison of full-frame and APS-C sensor sizes