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Focal length and perspective: an explainer

By November 9, 2017 Photography No Comments

Perhaps one of the greatest myths about lenses in photography is that focal length affects perspective.

So, you might hear or read something about wide-angle lenses increasing the space between elements in the frame to ‘expand’ the perspective, while telephoto lenses stack elements in the frame together to ‘compress’ perspective. There’s no disputing that it can look like this is happening, but be assured that it is not the focal length of the lens that’s doing it.

The fact is, it’s the camera-to-subject distance that determines perspective, nothing else. The reason people confuse this with focal length is because wide-angle lenses are typically used closer to the subject, while telephoto lenses are usually employed from a greater distance. Still sceptical? Then perhaps the examples shown here will help clear things up.

The images above are views of London’s Shard building, taken moments apart from the same position. The far left image was taken using a 28mm wide-angle focal length setting and the central image was taken at a 200mm telephoto focal length.

At first glance, the perspective looks radically different: the wide-angle image appears to exaggerate the space between near and far, while the buildings in the telephoto shot appear to be very close together. This would seem to support the idea that wide-angle and telephoto focal lengths deliver a different perspective. However, look what happens when the wide-angle image is cropped to match the framing of the telephoto shot (above right). Sure, the image quality isn’t as good (it’s a pretty severe crop, after all), but the image has an identical ‘stacked’ perspective to the telephoto shot.

The conclusion? Wide-angle and telephoto lenses may appear to deliver different perspectives, but the reality is, the perspective is identical. It is only the lens-to-subject distance that changes perspective.

Perspective changes only with distance. This sequence was shot using a range of focal lengths (28–450mm equivalent), while keeping the subject approximately the same size in the frame. This meant moving closer to the subject when using a wide-angle lens and backing away to use a telephoto lens.

This has a significant effect on perspective: shooting close with a wide-angle lens seems to increase the distance between the foreground and background elements, while shooting from a greater distance with a telephoto lens really compresses the perspective. You can see this most clearly in the shadows in the pictures: notice how the shadows in the distance appear to draw closer to the subject as the focal length increases, and also how the shadow she is casting becomes shorter. It’s also worth noticing what happens to the path: the sides appear to converge far more aggressively the wider the focal length is.

However, it’s worth repeating that it is the camera-to-subject distance, and not the focal length that is performing this visual trickery.

Complete Photography is Chris Gatcum’s 400 page guide to take you from beginner to expert photographer. Take the guest work out of your picture-taking and understand not just what to do with your camera, but how and why this affects the photos that you take. Whatever your camera, learn how to make a bigger, better impact with your photos.

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