What is Focal Length? (Why it Matters in Photography)

One of the most important aspects when you buy a lens is the focal length. This lets you know how close you need to be in relation to the subject you are capturing.

A longer focal length is necessary for objects further away. A smaller focal length captures more of the scene in front of you. To understand focal length in four, easy steps, read on.

Why Focal Length Is Important

Knowing what focal length means in relation to your camera is very important when it comes to buying lenses. Read this post to find out what different lenses are used for. You’ll see which ones are right for you how to use them creatively and all the technicalities.

Lenses are divided into two categories based on whether they can zoom. There are the ones that have a fixed focal length (prime lenses). And there are those that have a variable focal length. In general prime lenses are sharper and often have a wider aperture. These are great for low light conditions.

Zoom lenses allow you to use one lens to cover a range of different photography fields. One lens means less time spent searching for and changing lenses. There are advantages and drawbacks to both types of lenses. So having a mixture of them gives you versatility and power.

We can use the human eye as an example. Its focal length varies between 17mm and 25mm, depending on who you ask and who you examine.

We have an approximate field of view of over 180°. This is different from the 90° angle of view from a lens, which is down to the fact that we have two eyes.

The area that we actively perceive is similar to a 40-50mm lens. That’s why the 50mm is called the ‘standard’ focal length.

Step 1 – What Does Focal Length Mean?

The focal length of the lens determines how ‘zoomed in’ your photos are. The higher the number, the more zoomed your lens will be.

It is often misunderstood that the focal length is measured from the front or rear of the lens.

In reality it’s the distance the point of convergence in your lens and the camera sensor. This is the case of simple lens designs (like Double-Gauss). There are also plenty of complex optical designs that work differently. In many cases that distance is not equal to the focal length.

The key takeaway is that the focal length of a lens is identical to the focal length of a single lens that would provide the same field of view.

Step 2 – Different Focal Ranges and What They’re Used For

Ultra Wide Angle and Fisheye 14-24 mm

These lenses are often considered specialty items. Usually they are not included as part of a starter kit. They create such a wide angle of view that can feel unnatural to work with at the beginning. This is down to the lens having to fit more of the scene into the image than what your eyes can see at once.

Ultra wide-angle lenses are often used in event and architectural photography. They help to get a lot into a photo when shooting in a confined space.

These lenses are not suitable for portraits. They enhance the perspective so much that facial features can look unnatural.

Landscape photographers and adventurers however love them. An ultra-wide lens is able to perspective in ways that these genres value. In a landscape scenario it’s possible to have a flower in the foreground be larger than the mountain in the background while still fully including both in the frame.

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