Classifying Camera Lens Focal Length: Long vs Short
When discussing camera lenses, the terms 'long' and 'short' are often used to describe the focal length of a lens. However, understanding these terms accurately and learning how to classify a lens based on its focal length can greatly improve your photography skills.
Introduction to Lens Focal Length
Lens focal length refers to the distance from the optical center of the lens to the image sensor or film plane when the subject is in focus. This is a critical parameter that determines the magnification of the subject and the field of view (FOV).
Normal Focal Length
The 'normal' focal length is the one that provides a viewpoint similar to the human eye. For a full-frame (FF) sensor, this focal length is usually 50mm. This focal length is often considered the sweet spot due to its balance between moderate magnification and wide viewing angle.
Long Focal Length Lenses
A lens with a focal length that is greater than the normal focal length for the sensor or film format can be considered 'long.' These lenses are often referred to as telephoto lenses. Examples include 85mm, 135mm, and 300mm lenses for full-frame cameras. Long focal length lenses are characterized by their ability to capture subjects from a distance while maintaining high image quality.
Short Focal Length Lenses
A 'short' focal length lens, on the other hand, has a focal length shorter than the normal focal length. These lenses are also known as wide-angle lenses. Examples include 24mm, 35mm, and 20mm lenses for full-frame cameras. Short focal length lenses are great for capturing wide scenes and creating dramatic effects due to their expansive field of view.
Telephoto and Wide-Angle Lenses: A Closer Look
Telephoto lenses are a subset of long focal length lenses that are designed to capture distant subjects with greater magnification. They are useful for sports, wildlife, and portrait photography. However, these lenses can suffer from barrel distortion and chromatic aberration.
Wide-angle lenses, which are typically considered short focal length lenses, offer a wide field of view and can create interesting visual effects. They are popular for landscape photography and urban explorations. However, they can introduce perspective distortion.
Classifying Focal Lengths Across Sensor Formats
It's important to note that the classification of 'long' and 'short' focal lengths can vary depending on the camera sensor format. For example, a 50mm lens on a full-frame camera is considered 'normal,' but the same lens on a crop (APS-C) sensor camera will have a field of view equivalent to an 80mm lens on a full-frame camera. Hence, the classification of focal lengths depends on the sensor or film format.
Conclusion
Understanding the difference between long and short focal length lenses can help photographers choose the right tool for their creative needs. Whether you're aiming to capture distant subjects through a telephoto lens or want to include as much of a scene as possible with a wide-angle lens, knowing how to classify and utilize different focal lengths is essential.
By mastering the use of these lenses, photographers can expand their creative capabilities and produce stunning images that truly represent the essence of their subject matter.