What Is a Fast Lens?

What Is a Fast Lens featured photo

When shopping for a lens, you have probably heard the term “fast” lens. If you are confused, you are not alone. I also encountered this lens type and wondered how it could be fast. I eventually learned its meaning, which I will share with you below.

A fast lens describes any lens with a wide maximum aperture. It lets more light inside the sensor. This larger lens opening allows you to use a faster shutter speed, hence the name “fast” lens.

A fast lens offers many benefits to suit different types of photography. This article will thoroughly cover these advantages. But first, I will teach the in-depth meaning and applications of fast lenses.

What Is a Fast Lens?

What Is A fast Lens

A fast lens has a large maximum aperture. The greater the aperture, the faster the lens.

The aperture refers to the lens opening that allows light inside the image sensor. It is usually expressed in f-stops or f-numbers. 

A small number, such as f/2.8, describes a lens with a large aperture. It lets more light hit the sensor. In contrast, a large figure like f/16 has a small lens opening. It can limit the amount of light entering the camera.

A fast lens usually has a maximum aperture of f/3.5 and wider to capture more light. It allows you to use a faster shutter speed, like 1/100 and above. That is where the name of the lens comes from.

What Are Fast Lenses For?

Fast lenses are suitable for different photography types and techniques.

One of the most common uses of fast lenses is handheld shooting. They enable you to use fast shutter speeds at a given amount of ambient light. Hence, they make it possible to take photos handheld without worrying about camera shake.

Fast lenses also suit action and sports photography. They can freeze the subject in motion and retain most details because of the fast shutter speed. 

As their name suggests, fast lenses are also excellent for capturing fast-moving objects. These include airplanes, birds, cars, and people jumping or running around.

Moreover, fast lenses are ideal for portrait photography. They have a wide maximum aperture that lets more light inside the sensor and creates a shallow depth of field. These factors help you capture stunning portraits.

Finally, these types of lenses are great for astrophotography. They have excellent low-light capabilities that can shoot the stars and other celestial bodies.  

What Are the Advantages of a Fast Lens?

A fast lens offers several benefits, making it a top choice among photographers. Below are the advantages of a fast lens to help you decide if it is the proper camera gear.

Better Low-Light Performance

Better Low-Light Performance

As previously mentioned, a fast lens has a wide maximum aperture or a large opening. It allows more light to enter the camera.

So whether you are taking photos in a dimly lit room, after sunset, or at night, using a fast lens makes all the difference. It gives you more flexibility when choosing the proper camera settings.

For example, if you want to shoot the night sky, you can easily adjust the aperture and shutter speed without worrying about camera shake. Doing so can help the sensor capture the smallest amount of available light in the scene. The lens can retain all the details, resulting in stunning photos. It can even make the night look like day in some instances.

Faster Shutter Speed

A fast lens also lets you shoot at a faster shutter speed. This camera setting can prevent camera shake and motion blur in your photos. It is essential in several photography types, such as action, sports, and wildlife photography.

As a rule of thumb, avoid using a shutter speed of 1/60 second and slower, especially when shooting handheld. It can produce slightly blurred images because the camera is not fast enough to freeze your natural hand movements.

But if you must shoot at 1/60 second or slower for whatever reason, having a fast lens is beneficial. You can adjust the aperture to let more light in. With this extra amount of light, you can slightly increase your shutter speed to minimize blur.

A slow lens is unable to offer these benefits. It forces you to increase the ISO or use a tripod to compensate for the slow shutter speed. Both instances are not always ideal, though. First, a high ISO setting can introduce grain to your photos. Second, setting up a tripod is inconvenient in small spaces.

Shallow Depth of Field

Shallow Depth Field

Besides a wide maximum aperture and a fast shutter speed, a fast lens can also produce a shallow depth of field. 

The depth of field describes the area within an image that appears sharp and in focus. It determines how much background blur is in the scene. 

A shallow depth of field softens the background and makes the subject stand out in the frame. It is popular in portraiture, wildlife, and other types of photography.

Use a fast lens with a maximum aperture of f/3.5 and wider (f/2.8, f/1.8, f/1.4) to achieve a shallow DoF.   

What Are the Disadvantages of a Fast Lens?

Although a fast lens offers many benefits, it also has its share of disadvantages. 

Consider these drawbacks before buying this type of lens.

High Price Tag

A fast lens is more expensive than a slow lens with the equivalent focal length. For example, the Canon 24-70mm is available in an f/2.8 and an f/4 version. The former is a couple of hundred dollars pricier than the latter.

However, there are several reasons why fast lenses have a high price tag. For one, these lenses have better lens construction and capabilities. These features ultimately increase the cost of the lenses.

It is up to you to decide if you want to pay a premium for faster lenses. Most beginners or hobbyist photographers would find these lenses too expensive for their needs. But if you are serious about photography, you will likely consider them worth buying.

Bulky and Heavy

Besides being expensive, a fast lens tends to be bulkier and heavier than a standard lens. It has larger glass elements to provide a greater aperture and higher image quality.

Heavy lens construction is not necessarily a con. In fact, some photographers prefer a lens with some bulk in it because it indicates a premium build.

But those who often travel will find the heavy fast lens a liability. You will feel tired faster than usual. This might eventually lead to using accessories like tripods and gimbals, which are more hassle to bring while traveling. 

Poor Autofocus Performance

A fast lens lets you shoot at extremely wide apertures of f/1.8 or f/1.2. While it allows more light in the scene, it also produces a very shallow depth of field. It is so shallow that you could capture a portrait with one eye in focus and another out of focus.

This small focus plane forces the built-in autofocus feature of the lens to work harder. However, it often struggles when focusing on a subject with these wide apertures.

Consider manual focus or a relatively small aperture (f/2.8 or f/3.5) to ensure sharper images.

Fast Lens vs. Slow Lens Speed: Meaning Explained

A fast lens has a large maximum aperture of f/3.5 and wider. The name comes from the lens’s ability to shoot at fast shutter speeds.

In contrast, a slow lens has a lens opening of f/4 and narrower. It can limit the amount of light entering the image sensor. And to compensate for the lack of light (due to the small lens opening), it forces you to use slower shutter speeds. 

Both fast and slow lenses have pros and cons. 

As previously mentioned, fast lenses offer better low-light performance. They also create a shallow depth of field. They are suitable for astrophotography, portraiture, sports, and wildlife photography. However, these types of lenses could be expensive and heavy.

Slow lenses are more affordable than fast lenses. They are also lightweight, making them popular among beginners and travelers. They can even handle photography genres that do not require a shallow depth of field, such as architecture and landscape.

Unfortunately, slow lenses also have several downsides. They have poor low-light capabilities. They also cannot freeze the action as effectively as fast lenses.

Popular Examples of a Fast Lens

Below are several popular fast lenses you can buy today.

  • Canon EF 50mm f/1.2 L USM Lens
  • Canon EF 50mm f/1.8 STM Lens
  • Canon EF 85mm f1.2L II USM Lens
  • Canon EF 70-200mm f/2.8L IS III USM Lens
  • Nikon AF-S NIKKOR 50mm f/1.4G
  • Nikon AF-S NIKKOR 50mm f/1.8G
  • Nikon AF-S NIKKOR 14-24mm f/2.8G Lens
  • Sony FE 50mm f/1.4 GM Lens
  • Sony FE 16-35mm f/2.8 GM Lens
  • Sony FE 24-70mm f/2.8 G Lens


You probably felt confused when you first heard about fast lenses. Fast lenses have a large maximum aperture, which lets more light inside the image sensor. They enable you to use a fast shutter speed, hence the name.

Do you have more questions about fast lenses? Visit our contact page to send your queries.