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What is Focal Length in Photography [Beginner’s Guide]

Rajib Mukherjee Avatar
Rajib Mukherjee
18 January, 2023 • Updated 14 days ago
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Focal Length in Photography
Focal length is often a misrepresented and misunderstood term in photography. Focal length has nothing to do with the length of the lens itself. Focal length represents the distance between the point where the rays of light converge to form a sharp image of a subject and the imaging sensor at the back of the camera. This distance is always measured in millimeters except when the lens is focused – then the focal length is set to infinity.

Focal length is a good indicator of the lens’s angle of view. The angular view of the lens indicates how much of the scene in front of the lens will be captured by the camera. The shorter the focal length, the wider the angle of view, and therefore the larger the section of the scene in front of the lens captured by it. Conversely, the longer the focal length the smaller the angle of view of the lens and the corresponding section of the scene captured.

How Many Different Types of Focal Lengths are There?

In very generalistic terms, there are three types of focal lengths. these are:

  • Wide-angle focal lengths
  • Standard focal lengths
  • Telephoto focal lengths

There are multiple sub-genres of focal lengths underneath these three basic types of focal lengths, including:

  • Ultra wide-angle focal lengths
  • Wide-angle focal lengths
  • Standard focal lengths
  • Short telephoto focal lengths
  • Medium telephoto focal lengths
  • Super-telephoto focal lengths

Uses of a Wide-angle Lens

green trees near lake during daytime

Wide-angle lenses have a shorter focal length and, therefore, can capture more of the scene. These lenses are ideally suitable for capturing landscape photography. They’re also used for capturing architectural photography, weddings, group photos, cityscapes, and any other genre of photography where a wide-angle view is required.

Uses of a Standard Lens

person holding black camera lens

A standard lens is considered a versatile, all-purpose lens. A focal length of around 50mm is considered standard for shooting everyday photography with a full-frame camera. Similarly, if you’re using a crop camera, a focal length of approximately 35mm is considered standard. 

You can use standard lenses for shooting photos on the streets, in the great outdoors, or to capture portrait photography. Especially when shooting with a crop camera, as crop cameras with their 1.6x and 1.5x crop factors push the focal length up. A standard lens like a 50mm prime becomes the equivalent of a 75mm or an 80mm lens – good enough for portrait photography.

The fast aperture of most wide-angle lenses allows you to blur your images’ foreground and background and highlight only the subject. It is an excellent lens for creating beautiful background bokeh.

The fast apertures also make wide-angle lenses ideal for freezing the moment. If you’re using a fast aperture lens in a well-lit environment, you can use a fast shutter speed, allowing you to capture action shots.

Uses of a Telephoto Lens

person holding black camera with telephoto lens

Telephoto lenses are designed to be able to capture images of objects that are a considerable distance from the camera. These lenses have a high magnification ratio and compression. They are ideal for genres such as wildlife and sports, as it can be hard to get close to the subject in these circumstances.

Another great thing about these lenses is that they produce a tight composition and capture facial features very well, ensuring that these lenses are suitable for portraits. Examples of such lenses are the 70-200mm and the 24-105mm lenses. Longer focal-length telephoto lenses are also available.

Depth of Field and Focal Length

purple flower and fly in tilt-shift lens

Depth of field (DoF) indicates the amount of the image that’s in focus. When you’re tinkering with lenses, DoF tends to change. DoF depends on the focal length that you’re using as well as the aperture. The shorter the focal length, the wider the DoF for the same aperture, and every other aspect of the camera remains the same. Again, the wider the aperture, the shallower the DoF when every other aspect remains the same. Let’s look at a few examples to understand this.

Let’s say you’re using a full-frame camera with a focal length of 200mm and an aperture of f/2.8. You will get a very shallow depth of field. Let’s say that you now switch to an aperture of f/11. Your DoF will change and become larger.

Let’s say you now switch to a focal length of 24mm and an aperture of f/2.8. You can get a decent field depth depending on where you’re focusing. If you switch to an aperture of f/11, your DoF will be more significant.

DoF does not depend on the crop factor of a lens. If you’re to take a picture of an object using a 70mm focal length on a full-frame camera and then use a crop sensor camera to take the same picture from a distance, the image will appear zoomed in. However, if you crop the image taken with the full frame camera and match the image with that of the crop camera, you will notice that the two images show identical DoF.

Conclusion

The focal length determines how much of the scene a lens can capture. This ensures that your lens can make a tight or wide composition. To experiment with your composition, you must understand how focal length affects the composition. We hope this article has helped you understand everything you need to know about focal lengths.

Rajib Mukherjee Avatar
Written by
Rajib Mukherjee
Rajib is an avid travel photographer and an overall shutterbug. The first time he ever clicked an image was with an Agfa Click IV back in 1984. A medium format film camera. From that auspicious introduction to photography, he has remained hooked to this art form. He loves to test and review new photography gear. Rajib travels quite a lot, loves driving on Indian roads, playing fetch with his Labrador retriever, and loves photography. And yes, he still proudly owns that Agfa Click IV!
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