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Focal length comparison

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by David Em
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The focal length of your lens indicates the angle of view. It determines how much of the scene will be captured in your image, and the size of your subject.

Estimated reading time: 7 minutes

3 images of a person showing different focal lengths.

Understanding focal length

Focal length, which is represented by millimeters (mm), is the main measurement of a camera lens. Knowing what it means and how it works is crucial when it comes to buying a lens.

Related: Canon EF to Sony adapter guide

It’s determined by measuring the distance between the camera sensor and the point of convergence when the lens is focused at infinity. This is where the light rays intersect, and the digital sensor receives a sharp image.

A shorter focal length means that the angle of view will be wider, whereas a longer focal length results in a narrower one. This is the difference between wide-angle and telephoto lenses.

The following is a diagram of how focal length works:

Diagram of how focal length works.
Focal Length Diagram by David Em/Portraits Refined

The result is upside down because the image that’s projected to the camera sensor is inverted and digitally flipped right side up.

Related article: How to use diagonal lines in photography

Focal length comparison

In this focal length comparison, we used a 24mm, 50mm, and 100mm lens to show the same picture at different focal lengths. All of the images were shot using the aperture f/2.8.

3 portraits showing different focal lengths.
Focal Length Comparison. Photo by David Em/Portraits Refined

The following gear was used for the image:

The two main differences are how the subject looks and the background. At 24mm, you can see more of the background, with a sharp focus throughout the image, while the 100mm is narrow with a blurry background.

Longer focal lengths allow you to isolate the subject, while shorter focal lengths utilize the background as an important part of the scene.

Related article: The best Sigma Art lenses

Fixed vs. variable

Camera lenses are divided into two categories, fixed or variable. The categories are based on whether or not the lenses can zoom.

A fixed focal length, also known as a prime lens, can’t be changed. A lens with a variable focal length is also known as a zoom lens where the focal length changes by using the zoom ring.

Related: Prime vs. Zoom Lens

Classifications

The best lens for you depends on the purpose and types of photos you’re shooting. The following are the different focal length classifications and what they’re best for:

Wide-angle lens

Sony wide-angle lens.
Sony G Master FE 24mm F1.4 GM Wide-Angle Prime Lens. Photo courtesy of Amazon.

Wide-angle lenses are great for capturing a large portion of the scene. You’ll be able to take a photo of almost everything that you can see in front of you.

Full-Frame: 14mm – 35mm

Crop Sensor: 10mm – 24mm

Best for: Landscapes and Real Estate (exterior and interior).

Standard lens

Sony standard lens.
Sony FE 50mm F/1.8. Photo courtesy of Amazon.

Standard lenses are similar to what the human eye sees. It’s a versatile lens that can be used for many types of photography.

Full-Frame: 50mm – 60mm

Crop Sensor: 24mm – 35mm

Best for: Portraits and Real Estate.

Telephoto lens

Sony telephoto lens.
Sony FE 70-200mm f/2.8 GM OSS E-Mount Lens. Photo courtesy of Amazon.

Telephoto lenses compress the image, which means it’s harder to tell what the distance is between your subject and objects in the photo. This lens is great for getting up close, especially when the subject is further away.

Full-Frame: 70mm – 200mm

Crop Sensor: 55mm – 200mm

Best for: Portraits, Weddings, and Wildlife.

Super-telephoto lens

Sony super-telephoto lens.
Sony FE 400mm F2.8 GM. Photo courtesy of Amazon.

Super telephoto lenses take telephoto to the next level. They’re best for taking photos of distant subjects with clarity and sharpness.

Full-Frame: 300mm+

Crop Sensor: 200mm+

Best for: Wildlife and Sports.

Macro lens

Sony macro lens.
Sony FE 90mm f/2.8 Macro G. Photo courtesy of Amazon.

Macro lenses are specialty lenses designed to photograph close-up images of small objects. They typically have a Magnification Ratio of 1:1. The Magnification Ratio is the relationship between an object that’s focused correctly on the sensor and the subject in real life.

Generally, 40mm and above are the best focal lengths for macro lenses.

Using a teleconverter

Canon 2x teleconverter.
Canon 2x Teleconverter

A teleconverter is a magnifying lens that’s used between the camera body and lens that you’re using. They work best when paired with high-quality glass because it slows down the speed of your lens and overall sharpness.

Depending on which teleconverter you buy, they can magnify the focal length by 1.4x, 1.7x, and 2x. This means that you can lose up to 2 stops of light.

If you’re shooting with the Sony 300m f/2.8 and used a 2x teleconverter, the result would be 600mm f/5.6, and the image won’t be as sharp.

The benefit of using one is that they’re cheaper than buying a super-telephoto lens.

For example, the Canon EF 600mm f/4L IS III USM Telephoto Lens is $12,999. To save money, you can buy the Canon 300m f/2.8 for $6,099 and use a 2x teleconverter for $429. This would result in a 600m f/5.6, but the downside is that you’ll lose sharpness. However, the cost difference is $6,528 vs. $12,999, that equals $6,471.

If you want to save even more money and you’re fine with an aperture of f/8, buy the Canon 300mm f/4 for $1,349. The total for this set up would be $1,778.

Conclusion

The understanding of focal length is essential for purchasing or choosing a lens for a photoshoot. Remember, short focal lengths means wide-angle images, while long focal lengths mean a more magnified image.

More resources:

Photo of Sapana from Real + Vibrant by David Em Photography.

About David Em

David Em.

David Em is the founder of Portraits Refined. He’s a published portrait photographer dedicated to helping photographers develop skills, capture incredible photos, and build successful businesses.

About Portraits Refined

Portraits Refined (PR) is a media company that publishes the latest expert-backed portrait photography tips, in-depth camera gear reviews, and helpful advice to grow your photography business.

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