Focal length is an important attribute of lenses, particularly in photography. Understanding focal length makes a great leap forward in your photography.
Focal length is the distance from the lens to where the light collects into one point - the focal point. In photography, long focal length makes the subject more magnified and narrow the angle of view. A short focal length implies the opposite: less magnification and a wider angle of view.
Understanding Focal Length and How Focal Length Changes Your Image
Difference Between Zoom Lens and Prime Lens
A zoom lens is a camera lens that has an adjustable focal length. On the other hand, a prime lens only has a fixed focal length that cannot be adjusted.
In general, prime lenses are specialist lenses that do better than zoom lenses at their specific focal length. Prime lenses tend to be cheaper, lighter, and faster than zoom lenses.
Zoom lenses are generalist lenses. They are the best choice when you will need to use many different focal lengths in a short time period, such as shooting an event, playing kids, or in a travel trip.
The right kind of lens for you depends on the application and how often you will need to change zoom levels. Zoom lenses make it easier to take a variety of shots without having to move around while prime lenses give better quality and consistent perspective.
Different types of lens
Zoom and prime lenses are the most important divisions among lens types. However, there are different types of lenses depending on their intended role.
- Wide Angle Lens: Made to take big, open shots. They can incorporate subjects deep in the background and combine them with the foreground. Great for landscape, cityscape.
- Standard Lens: Made for images at about the scale of human vision. Great for shooting portraits.
- Telephoto Lens: Have long focal lengths, normally 70mm or above, and are meant for focusing on far-away scenes. Great for portraits, sports, wildlife.
- Super Telephoto: Offer the strongest power of shooting far away subject. Any range longer than 300mm. Dream lens for every bird, wildlife photographer.
Focal Length vs Perspective
Focal length can affect the perspective of a shot.
A shorter focal length, as with an ultra-wide lens, will cause objects in the background to appear far away from the foreground and be spread apart from each other.
As the focal length increases, the background moves in closer to the foreground, and objects in the background move closer to each other.
This variety of perspectives can all be achieved by standing in the same spot and taking shots with different lenses. The best lens to have on hand depends on what you want to do in your photos.
Focal Length vs Depth of Field
The depth of field of a picture is the area with the sharpest focus.
Normally, the depth of field of an image is not affected by the focal length of the lens. Two shots taken with the same aperture but different focal lengths, will have different depth of field.
The shot with longer focal length will give shallower depth of field. Longer focal length requires a larger aperture size to give same f-number. Therefore, under same f-number, longer focal length give shallower depth of field.
Learn more: Calculation of Aperture Area
Therefore, a longer focal length will tend to blur the background more strongly. It can also make the subject stand out more.
Understanding focal length is an important set of knowledge for photography. It can affect your shot in multiple different ways and interact with other attributes of the lens and the camera.