Unfortunately we’re not going to be able to make all of these lessons simple. Focal length is where the rubber starts to meet the road. No one said photography would be all fun and games! The sound of rubber hitting the road is the photographers who don’t want to understand the basics of photography and are now switching their cameras to the Auto mode.
Focal Length is the distance from the middle of the lens you’re using to the camera’s image sensor. Understanding focal length is important because it’s one of the three factors that determine your depth of field. Depth of field is our next lesson, so it’s important that you understand focal length.
Focal length determines how much of a scene the lens is allowed to see. This translates to the camera’s angle-of-view. A short focal length allows the camera to have a wide angle-of-view. This allows you to capture a large part of the scene. A long focal length shortens the camera’s angle-of-view, which results in the camera being able to ‘see’ a narrower part of the scene.
Short focal length = wider angle-of-view = more of the scene
Long focal length = narrower angle-of-view = less of the scene
The above explains why telephoto lenses bring subjects up closer and why shorter lens take wider pictures. The amount of magnification in an image is determined by the focal length of the lens. Micro lenses are normally very short. With the wider angle-of-view, they bring the subject up closer. Telephoto lenses have a narrower angle-of-view and focus on less of the scene.
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