How to Use Still-life Subjects to Understand Focal Lengths

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Do you think that using an 18mm lens or a 100mm one will only zoom in or out your scene? Why are camera lenses are measured in millimeters? Do you know what those measurements mean for your photo? If you’re not sure which lens to use and why I invite you to keep reading and learn about focal lengths and how to use them.

The most common consideration when choosing your lens is whether or not you need to zoom in or zoom out. Therefore logic dictates that you would use a wide-angle lens for landscape photography and a telephoto for a detail of that landscape. Another well-known factor is the distortion of wide-angle lenses, so for example, if you want to do a portrait you would instead use a normal or a telephoto lens.

But how about shooting objects or photographing still life subjects? Which lens is better? I’ll use this subject to illustrate the characteristics of different focal lengths that normally get less attention.

What is focal length?

When light comes in through the lens, it passes through a small hole called a nodal point. The distance from that point to the sensor when your lens is set to infinity is called the focal length and this is measured in millimeters. A smaller distance gives you a wider angle of view and that’s why it’s called a wide-angle lens. Therefore a bigger distance gives you a narrower angle of view which is called a telephoto lens.

What is normal?

When you say a normal lens, it means that it will see more or less the same angle of view as the human eye. Anything longer than the normal focal length is a telephoto and everything shorter is a wide-angle lens. This measurement depends on the size of your sensor because the measure of its diagonal is what determines “normal” for that camera.

For example, in analog photography, it was a very standard measure because there were only so many negative film formats. A 35mm film had a normal lens of 50mm, this can be translated into digital cameras that have a full frame sensor because it’s about the same size as 35mm film. If you have a cropped sensor camera, that “normal” lens becomes a telephoto.

Left – longer lens more zoomed in. Right – wider lens more zoomed out.

Why is this important?

As I mentioned before, zooming in or out is the most obvious impact of the focal length. But what happens when you are shooting something where you can achieve that by getting closer or further from your subject? How do you choose your lens? Well, that’s where the other characteristics of the focal length come into play.

Compression

A photograph is a two-dimensional representation of a three-dimensional world. By changing the focal length you can compress or extend the distance between two objects, or between the subject and the background. Let me show you with a series of images taken of the same scene but with different focal lengths.

I put a measuring tape next to the objects so that you have a reference and see that they were separated by the same distance even if it doesn’t look like it in the various images.

18mm lens.

35mm lens.

55mm lens.

Notice how the distance between the shells seems to change. With wide-angle lenses, things will seem further apart from each other, compared to how they look with a telephoto lens. Now, you probably also perceived another difference between the images, and that is the focus. Which brings me to the second characteristic.

Depth of field

As you probably know, the depth of field (area in focus) depends on the aperture. A small aperture gives you a greater depth of field than a big one. But there is another factor involved and that is the focal length.

A wide-angle lens appears to have a greater depth of field than a telephoto at the same aperture. It is a common misconception that wide-angles have more depth of field than longer lenses. The reason it appears so has to do with the subject to camera distance, not focal length.

This effect is intensified by the fact that you will be physically closer or further away with each lens to achieve the same framing. Allow me to illustrate with this photos in which I maintained the same aperture but changed the focal length.

180mm - Using still-life to understand focal length

180mm

160mm - Using still-life to understand focal length

160mm

100mm - Using still-life to understand focal length

100mm

70mm - Using still-life to understand focal length

70mm

55mm - Using still-life to understand focal length

55mm

35mm - Using still-life to understand focal length

35mm

18mm - Using still-life to understand focal length

18mm

See how the photo taken with a 180mm lens has such a shallow depth of field that the blurry background even creates a halo that comes over the sharp focus subject. After that, each image got greater and greater depth of field by using smaller focal lengths.

Conclusion

In conclusion, there is no such thing as the best lens for the type of photography you are doing. It really depends on the results you want to get.

Read more from our Tips & Tutorials category

Ana Mireles

is a photographer and artistic researcher. She has been awarded and exhibited in Mexico, Italy, and the Netherlands. Through theory and practice, she explores the cultural aspect of photography, how it helps us relate to each other, the world, and ourselves. She has also a passion for teaching, communication, and social media. You can find more about her and her work at her website or acquire some of her works here.

  • Heather

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  • Robert Campbell

    Please note that the text on the first photo in the Depth of Field section says 1800 mm rather than 180 mm. But aside from that I enjoyed your article. It will help those who need a more clear understanding of the subject. Thank you!

  • Ana Mireles

    Thank you Robert, I’m glad you liked it. And thank you for bringing our attention to the mistake in the focal length!

  • Fixed, thanks for finding that Robert

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  • Verkeys Francis

    Great article. specially the first topic “compression”. I liked it. thank you for sharing

  • walwit

    I think I didn’t understand you very well, do you maintain the same subject to camera distance in all those photos?

  • Ana Mireles

    Thanks for your comment, I’m so glad you liked it 🙂

  • Ana Mireles

    Hi walwit. No, In order to keep more or less the same frame I was adjusting my distance.

  • walwit

    How can your experiment leads to any conclusion if you are changing both, the focal length and the distance?

  • Ana Mireles

    Well the article is not meant to be an experiment like in science to reach an indisputable fact. It’s more like a creative exercise. Most photographers have different focal lengths, either in different lenses or in a zoom lens, and the idea is to show the different possibilities you have with your gear. Focal length is more than zooming in or out, in a situation in which you can physically move closer or further to your subject, like this studio setting; why would you choose one focal length over the other? Because of the compression effect, or the distortion or the depth of field… that’s what the article shows: the different effects that you can get with different focal lengths, even if the subject or the framing is the same the result is not.

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