The focal length is an essential issue in photography because it varies according to the camera and lens used, so much so that it directly influences the image.
Therefore, throughout this article we are going to talk to you about what the focal length is and its importance, what are the different types of lenses that exist and other necessary questions to be able to get the most out of your equipment.
What is focal length or distance?
Also known as ‘ focal length ‘ in English, it is an optical characteristic in both lenses and mirrors. It is the parameter, expressed in millimeters , that expresses the distance between the optical center of a lens –we are talking about the point close to the diaphragm where the light rays converge– and the sensor or focal point.
In other words, it is the distance between the lens and the camera’s sensor , that is, the measure that can be seen when focusing at a distance.
It is intimately related to other aspects of photography such as composition, aperture and depth of field, because each zoom turn or lens shift affects your own vision and, therefore, your photography.
Types of focal length in photography
Let’s now look at the different types of focal lengths and their explanation :
Short focal length
A lens with a short focal length is less than 35mm . However, the viewing angle is wider, so you can capture a landscape in its entirety with it.
Photographs taken with this type of lens show some distortion, and while elements in the foreground or close-up are magnified , those in the background show a diminished perspective.
Medium or standard focal length
Although it has an oscillation range between 35mm-50mm , depending on the type of sensor, it is the one that shows a more natural perspective without distortions, since the field of vision they provide is very close to that of the human eye.
Long focal length
These kinds of focal lengths are greater than 50mm , so the angle of view is smaller compared to what you can see with your eyes.
Thus, an image taken with a 100mm lens will cover a smaller section, although elements taken at a greater distance will be seen with more quality and detail .
How is the focal length measured on your camera?
The focal length can be longer or shorter depending on the size of the sensor, so the longer the focal length, the further it will be from the lens physically; and other issues such as the angle of view will also vary, since changing the distance affects the visual field.
To calculate r multiplication factor , regardless of brand or model used you must have reference to the size of the camera sensor Full Frame (35mm) and using the following formula:
Sensor width (35mm) / Sensor width of your camera (value in mm)
To understand this question, let’s give you an example: a lens with a distance of 16mm is ideal for photographing landscapes , but the camera has an APS-C sensor, so the effective distance will not be 16mm but 24mm, since that the multiplication factor is 1.5x (1.6x in Canon). With this, the lens has an angle of view that does not allow to capture the same part of the scene as that shown with a full sensor or Full Frame.
Effects of focal length in a photograph and crop factor
The focal length has significant effects on a photo, since it is responsible for determining the angle of view of a lens: in long focal lengths the angle of view is small, and in short ones it is large.
This makes the feeling of closeness to the object to be photographed greater, since it brings scenes located miles closer together and, in addition, is responsible for also affecting the depth of field , that is, the part of the scene that is in focus.
Thus, the cropping factor affects your shots, since, although the apparent effect is to zoom, it is not really that the lens gets closer to the scene but rather a cropping effect after editing an image taken with a complete sensor.
Things to consider when choosing a goal
Now that you know what focal length is and how important it is, let’s expand on this information with other aspects that you should keep in mind when taking snapshots.
Focal length and angle of view
Both factors could well be synonymous . Most of the time when talking about focal length, what you are wondering is what angle of view the lens provides according to the camera.
In short, the angle of view is the ‘ part or area of the image ‘ that the subject captures measured in degrees . The more zoom, the less amplitude; while the more angular it is, the bigger scene you can see in the same photograph.
Types of objectives
The important thing in a lens is the angle of view , although they are generally classified according to their focal length. Look at the types that you can find in the market:
- Wide-angle lenses: these are lenses with focal lengths between 10-25mm with a viewing angle of 110º-60º, which offer the possibility of photographing urban or nature landscapes.
- Super wide angle : known as ‘fisheye’, they are a type of lens that has a focal length of less than 8mm and an angle of view from 180º.
- Standard lenses: the focal length is in the middle (35mm-50mm) while the angle of view ranges from 60º-25º. They are best suited for shooting a wide variety of scenes, from portraits to landscapes. Take a look at the article on the 35mm lens to find out why it’s one of my favorites.
- Short tele : they have a focal length between 65mm-100mm and a viewing angle of 25º-15º.
- Telephoto lenses : physically they are longer lenses and, although their angle of view is much smaller, they exceed the 50mm focal length.
- Super telephoto lenses : they cover focal lengths from 300mm. They are interesting for photographs at a very far distance. Those that cover a viewing angle of 10º-1º can reach up to 600mm focal length.
Goals with fixed or variable ranges
Each type of lens has its advantages and disadvantages ; Hence, choosing the most appropriate one will depend on your needs and your taste. Even with this, I am going to briefly explain what each of them implies to help you in your choice:
- Fixed focal lenses : as positive points they have higher optical quality, robustness and resistance in their manufacture; in addition, the lenses are brighter . However, for a good framing they require that you be the one who moves through the scene.
- Variable focal lenses : they are very versatile because they offer the possibility of having a greater focal variety in a single lens, although they are less bright and somewhat heavier and more fragile, as well as having a higher price.
The lenses have more or less distortion depending on the focal length . A standard one ensures that we see the image in a way more similar to how our eyes perceive it; however, a telephoto lens compresses shots and causes more blur. This also happens with the more angular lenses because by offering a greater depth of field they cause distortions in faces and lines.
An extra: Is using lenses for every occasion a good option?
Although in general you can take different shots with any objective, there are different types. Choosing the correct one for each scene is always a good option:
- For Transport (8mm-25mm) : a wide – angle closer than 25mm is one of the most recommended options to display most of the possible scene, even if it means a shorter focal length, since the end of these to mas is to transport the viewer to the place to see everything.
- For event’s social (25mm-135mm) : social photography covers a wide variety of planes, so it is essential that you are clear about what kind of thinking situations capture and where, as each has its pros and cons and it is not easy to choose between one focal point or another. To give you an idea, if you plan to take close-ups, you must have telephoto lenses or long focal lengths; But for full-body photography, a standard lens is best.
- For action images ( 7 0mm-200mm) : in this type of photos, you have to focus on a specific moment. The ideal option is to have a short tele or telephoto lens with a focal length of 70mm-200mm (or even 70mm-300mm) that allows you to be close and at the same time at a distance.
- For adventure images (100mm- 600mm ) : the recommended focal length starts from 100mm and could go up to 600mm, since the distance you can get to take these pictures is usually considerable: birds in flight, football matches, car races, animals in the wild… In this case, keep in mind that these lenses allow you to take shots from a great distance, but the risk of moving (jitter) is higher.
Throughout this article I have explained what focal length is, since it is a fundamental issue that affects any image. I hope I have helped you understand this complex concept, because, in addition to the quality of your camera and lens, the most important thing is your “eye” when photographing and your knowledge about it.