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The effect of focal length is easier to see if you use prime lenses as there’s a dramatic change when you switch from one to the other. It’s less distinct with zoom lenses.
For that reason it’s handy to think of a zoom lens as several focal lengths in one. For example, if you have an 18-55mm kit lens, you can think of it as three lenses with focal lengths of 18mm, 35mm and 55mm. Some zooms have important focal lengths marked on the barrel to help you with this.
That doesn’t mean you should ignore the in-between focal lengths as there are always times when they come in useful. But it will help you learn how those three important focal lengths work, and what the differences between them are.
In this example, the kit lens is a wide-angle lens at 18mm, a standard lens at 35mm and a short telephoto at 55mm. They behave quite differently. Understanding how the choice of focal length affects composition, as well as perspective and field of view, helps you choose the best one to use.
Lenses also have other characteristics that contribute to the look of the photo. One of these is bokeh, the aesthetic quality of the out of focus parts of the photo. Factors like the shape of the lens aperture and the quality of the lens elements affect the bokeh.
Focal length, aperture and composition
All these things influence your approach to composition.
It’s a good idea to ask yourself how to use the characteristics of your lenses to best effect. It’s about working work with your lenses rather than fighting against them.
For example, if you are using a telephoto lens is there a way you can use the compression effect – that is the way it magnifies the background and draws it closer to the subject – more creatively?
As you learn more about your lenses you will become better at selecting the best one to create the effect that you want.
Let’s look at some examples.
Sigma 50-150mm f2.8 lens
I used a focal length of 150mm and an aperture of f2.8 on an APS-C camera to create the above photo. It was made in the city of Potosí, Bolivia.
This is how the focal length and aperture affected the composition.
Narrow depth of field
The combination of wide aperture and long focal length means there isn’t much depth of field. Part of the background is out of focus which helps create separation between the woman and the buildings behind her.
The distance between the camera and the subject compress perspective, pulling the background close to the woman and baby. This is quite dramatic. Combined with the moody lighting it creates a cinematic effect similar to that used in some movies.
Narrow field of view
The telephoto lens has a narrow field of view and captures just part of the scene. This focal length is good for capturing detail, but not for including the entire scene.
Canon 85mm f1.8 lens
I used an 85mm lens on a full-frame camera to make this natural light portrait. I set the aperture to f2.8 to blur the background. This is a typical setting for portraits.
Narrow depth of field
Just like the first photo, this portrait has a shallow depth of field thanks to the wide aperture of f2.8. This helps separate the model from the background.
We made the portrait in a forest and I positioned the model in a shaft of light falling between the trees. As a result the background was darker than the model which also helped create separation.
The aperture choice, focal length and lighting worked together to create the effect I wanted.
It’s harder to see in this photo as the background is out of focus, but the compression effect evident in the first photo is also happening here.
Narrow field of view
The focal length may be shorter but there’s still a narrow field of view. The 85mm lens behaves in a similar way to the 150mm lens in this respect and you can’t see much of the background in the photo. This is another reason why an 85mm lens is such a good portrait lens.
Fujinon 35mm f1.4 lens
I made the candid portrait above with a 35mm lens, which is a standard lens on an APS-C camera.
Standard lenses occupy an interesting middle ground between telephotos and wide-angles.
Depth of field
An aperture of f4 means the background is slightly blurred but still recognizable.
Standard lenses are interesting – if you get close enough to your subject and use a wide aperture then you can throw the background completely out of focus.
But if you step back and use a smaller aperture the background comes into focus. In this sense a standard lens is extremely versatile.
Standard lenses are said to have a perspective similar to that of the human eye. A photo made with a standard lens doesn’t have the compressed perspective of a telephoto or the exaggerated perspective of a wide-angle.
Field of view
The wider angle of view means that you can fit more of the background into the frame compared with a telephoto lens..
I was able to make a portrait of the woman standing against the wall and include the background. This helps give the portrait a sense of place. Compare that to the previous images where you see far less of the portrait subject’s environment.
Fujinon 18mm f2 lens
I used an 18mm lens on an APS-C camera to create this landscape photo.
Wide depth of field
I used an aperture of f8 to get the entire scene in focus. This is different to the approach I used with in the earlier photos made with telephoto lenses, where I wanted the background to be out of focus.
Wide-angle lenses are ideal when you want lots of depth of field.
Wide-angle lenses encourage you to get close to the subject, which has the effect of pushing the background into the distance and making it seem further away.
Field of view
The wider field of view of wide-angle lenses mean that you can fit much more of the scene in the photo. That’s one of the reasons wide-angle lenses are popular for landscape photography.
Helios 58mm f2 lens
The Helios 58mm is an old, manual focus lens that you can use with most modern cameras using an adapter. It’s known for the swirly bokeh effect you get with the aperture wide open.
It’s a good example of how the optical qualities of the lens make a difference to the look and composition of the photo.
Learn more: How to Buy and Use Vintage Lenses
Hopefully the examples in this article help you understand how the focal length and aperture of your lenses affect the look of the photo.
With practice you will learn how to select the best focal length and aperture to create the effect that you want.
Let us know in the comments if you have any questions about lenses and composition.
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