Focal length

As you lift your camera to capture a scene, you ponder the concept of focal length. What exactly is focal length in photography, and how does it affect how your images turn out...

What is focal length?

The focal length is defined as the distance between the camera’s optical center (also known as its nodal point) and the camera’s center. Any photographer must have a working knowledge of focal length to shoot successfully.

The focal length of a lens determines the distance needed between a subject in order to photograph with precision. Without an understanding of camera focal length, photos risk appearing overly distorted or compressed. Essentially, the focal length is the lens’ optical property. Typically represented in millimeters.

A camera sensor is a hardware that captures light and converts it into an image. Photographers generally favor a 35 mm full-frame sensor type. Focal lengths are integral to photography because they indicate how ‘zoomed in’ an image appears. Once you know how focal lengths affect and relate to elements like zoom, perspective, and range, you can get creative with manipulating these features.

Before we continue, it is useful to go through several photography terms that are relevant to a focal length:

1. Angle of view

The amount of a scene captured by a camera’s sensor.

2. Zoom

Making an element appear closer without moving the camera. A powerful zoom can close in on an element without compromising the sharpness of an image.

3. Perspective

The sense of depth or spatial relationship between objects in an image. Focal lengths greatly impact the depth of an image.

4. Range

Also referred to as dynamic range, it is the ratio between white and black light intensities or the maximum and minimum tones in an image.

5. Aperture

Aperture is the opening of a lens which light passes through. Think of it as the pupil of an eye. The angle of view, zoom, perspective, range, and aperture are only a few important photography aspects related to focal length. Each element should be taken into account when considering what lens to use.

What are the lens types?

Lenses are generally categorized into two types according to their zoom capabilities. Deciding between the two usually depends on personal preference and the photography genre.

1. Prime lens

Prime lenses have fixed focal lengths, meaning that they do not have a zoom feature and have a more limited distance range for images. A prime lens's significant advantage is its ability to capture more light due to its wider maximum apertures. This makes them great for shooting in an environment with poor weather or dim lighting.

2. Zoom lens

A zoom lens is versatile because you can try various focal lengths with just one lens. They are a standard lens type for beginners. Let’s dive into the different lens focal lengths and how they affect composition, range, and perspective.

What are different focal lengths?

Simply put, a longer focal length shows a smaller angle of view and larger magnification, while a shorter focal length offers a broader angle of view and decreased magnification.

It is also important to note that while the lens controls the angle of view, the field of view is influenced by the focal length and the camera sensor.

1. Ultra wide-angle lens

An ultra-wide-angle lens measures 14 mm in focal length and usually exaggerates perspective in photography. Which makes it popular for shooting outdoor scenes like architecture or streets.

Photographers tend to use a lens with an ultra-wide angle when they want to capture as much of a scene as possible. A fisheye lens is an ultra-wide-angle lens that dramatizes an image, plays with the distance between objects, and provides a unique perspective to images.

2. Wide-angle lens

A wide-angle lens ranges between 24-35mm in-camera focal length. Like an ultra-wide-angle lens, it makes objects look smaller and can contain more within a frame. A wide-angle lens is often used when there is a large field of depth, making it perfect for shooting landscapes or cityscapes.

3. Standard lens

A standard lens has a focal length between 35 and 70 mm. It is generally considered a good choice for beginners. The most common standard lens is 50mm; it is also called mid-length. Many portrait photographers rely on standard lenses, which can also be utilized across an extensive range of image genres.

If you're a street photographer, then a 35mm is often a popular choice and many photographers have trouble between choosing a 35mm or 50mm lens.

4. Telephoto lens

A telephoto lens can range from a 70-300 mm camera focal length. It shows shallow depth and compresses the view, so it is typically used in environments where a photographer is far from their subject. For example, wildlife and sports settings. Beyond this, a super-telephoto lens exceeds a 300 mm focal length.

Why is focal length important in photography?

The focal length of the lens determines two important photography parameters such as magnification and angle of view. Photographers place a high value on it. Higher magnification corresponds to larger focal lengths and vice versa.

The camera's focal length affects not only how much of an object you can capture but also how large your objects will appear in a photo.

How do you choose focal length?

Every photographer should choose a focal length according to their needs. The filming genre, location, and artistic vision of the photographer determine the appropriate focal length.

Remember - the shorter the focal length, the more a scene is captured. The longer the focal length, the less of the scene is captured.

1. Wide-angle lenses

Wide-angle lenses (24mm - 35mm) are ideal for photographing landscapes, cityscapes, architecture, auroras, and the Milky Way. Wide-angle lenses are also good for indoor photography.

2. Fisheye lenses

A fisheye lens, also known as the ultra-wide-angle lens (4mm - 24mm), offers an enormous field of view and is mostly utilized for creative purposes.

3. Standard lenses

Standard focal length lenses (35mm - 70mm) are good for street, travel, and portrait photography.

4. Short telephoto lenses

Short telephoto lenses (70mm - 135mm) are preferable for street photography and portraits.

5. Medium telephoto lenses

Medium telephoto lenses (135mm - 300mm) photograph wildlife, sports, and action shots.

6. Super telephoto lenses

Super telephoto lenses (300mm+) are used to photograph sports from a distance, as well as nature and the night sky. Professional wildlife, sports, and astronomy photographers can benefit from telephoto lenses. However, keep in mind that telephoto lenses are heavy and may require the use of a tripod to support them.

Such lenses might not be suitable for amateurs, as they may exceed their budget.

How is focal length calculated in photography?

Finding the focal length of a modern lens is easy. The information is always printed on the lens. However, this does not apply to vintage lenses, so the focal length needs to be calculated manually.

The standard focal length formula is:

• 1/Focal length = 1/Image distance + 1/Object distance

Image distance and Object distance are provided in mm.

What is the focal length of a 50MM lens?

The focal length of a 50mm lens on a full-frame camera is 50mm. If you have a crop sensor camera, you should know that a 50mm lens will act differently. For example, if you use a 50mm lens on a crop sensor camera with a crop of 1.5x, you must multiply 50 by 1.5, meaning that the actual focal length for a 50mm is 75mm.

In conclusion, consider each element carefully before selecting the right lens and experiment with different focal lengths. There are many nuances when it comes to focal length. It could be fun to try out different focal lengths in order to see how they impact your image.

Still unsure about what to choose? Start standard and branch out from there. There are so many possibilities!