Playing With Focal Length and Manipulating the Background Without Changing the Foreground

Playing With Focal Length and Manipulating the Background Without Changing the Foreground

I guess you will have a zoom lens in your camera bag. It is a very handy tool that allows you to zoom in, and to zoom out. But you can also use it to manipulate the size of the background compared to your subject. Let me explain. 

We all love our zoom lenses. There are a lot of sorts, like a 8-15mm, 16-35mm, 24-70mm, 70-300mm, 200-600mm, and many more. It allows you to have every focal length available with just a few lenses. One could buy a 16-35mm, a 24-70mm, and a 70-200mm, and have every focal length between 16mm and 200mm available in just three lenses.

With only two zoom lenses you can have a focal range between 24 mm and 200 mm. This is the popular 24-70 mm and 70-200 mm lens from Canon, but almost all manufacturers have these two available. It is a wonderful basic set for most sorts of photography.

With only two zoom lenses you can have a focal range between 24 mm and 200 mm. This is the popular 24-70 mm and 70-200 mm lens from Canon, but almost all manufacturers have these two available. It is a wonderful basic set for most sorts of photography.

If you use only fixed focal lenses you would need something like a 17mm, 24mm, 35mm, 50mm, 85mm, 135mm, 200mm, and still missing all the focal lengths in between. Imagine what kind of camera bag you would need when carrying all those nice fixed focal lenses with you. One could argue if we really need all those focal lengths, but I don’t want to burn my fingers on that discussion. Fact is, zoom lenses are very versatile.

This set of four primes cover a good range of focal lengths, roughly similar to the two zoom lenses from the previous photo. But you need to carry four lenses instead of two, lens changes will be very frequent, and you miss a lot of focal lengths if you c

This set of four primes cover a good range of focal lengths, roughly similar to the two zoom lenses from the previous photo. But you need to carry four lenses instead of two, lens changes will be very frequent, and you miss a lot of focal lengths if you care about that.

Most of the times, we use our zoom lenses to zoom in. We like to have our subject large in the frame without the need to get closer. Sometimes we can’t get any closer, because the subject will run or fly away. Sometimes we just can’t get any closer because there is a physical barrier. Sometimes we just are too lazy.

You can manipulate the size of the subject through zooming, or by going closer. The latter is not always possible, as seen in this example.

You can manipulate the size of the subject through zooming, or by going closer. The latter is not always possible, as seen in this example.

For landscapes we often like to zoom out. It allows us to get even more of that beautiful landscape in the picture. For best practice we will try to have something in the foreground, a subject close by to give a feeling of depth. It gives the viewer a subject to look at and at the same time the photo won't look so empty.

It is important to have a subject in your landscape photo. If the subject has to be large in the picture, you have te get close to the subject when using a wide-angle lens. The background will be far away and small compared to the subject.

It is important to have a subject in your landscape photo. If the subject has to be large in the picture, you have te get close to the subject when using a wide-angle lens. The background will be far away and small compared to the subject.

Zooming in and zooming out is something we all do. It is the obvious way to use a zoom lens. But we can also use the focal length to manipulate the background. We all have seen the examples of a girl who is photographed with different focal lengths. To prevent the girl from getting any larger in the frame, the photographer is increasing the distance to that girl. 

With these kind of series we always focus on the subject, showing how more pleasing a person will become when longer focal lengths are being used. We don’t really see what is happening with the background. We take the background for granted, it is just there. 

Let's change the subject from a person to a landscape, and try to do the same thing. I have chosen a subject and photographed it with different focal lengths while trying to keep the subject the same size in the frame. For that, I needed to increase the distance to the subject with every longer focal length. Although the size of the subject does not change, the background is. With a longer focal length, the background becomes larger compared to the subject. It gives the suggestion that the distance between the subject and the background is decreasing, hence the popular statement: “tele-lenses compress distances.”

It is possible to manipulate the size of the background, while keeping the subject the same size. You need to increase the distance to the subject while zooming in. The subject will have the same size, but the background will change.

It is possible to manipulate the size of the background, while keeping the subject the same size. You need to increase the distance to the subject while zooming in. The subject will have the same size, but the background will change.

This effect is responsible for the nice background we see with long lens portrait photography. But we can also use this technique to manipulate the background in our photo. If the sky is boring, you might not want it to appear into the frame. A longer focal length can prevent that, while keeping the subject the same size in the frame. But you can also prevent having unwanted elements in the frame. Look at the before/after example below. The before photo is shot with a wide angle lens, close to the ferns. For the after photo I increased the focal length, and the distance to the ferns. By doing so, I excluded many white patches of sky.

Although wide-angle lenses make great compositions possible, you need to be careful for the deformation of subjects close by. This may not be visible in the average landscape photo, but it will become very clear when you have animals or persons as a subject. I have added two examples of this deformation. It might also be interesting to check what is happening with the elements in the background.

Changing focal length will change the size of the background relative to the subject. Just look at the sun in the previous before-after example with the dog. But also the Volkswagen van behind the wedding couple. Increasing focal length will increase the size of elements in the background, while the subject is almost the same size. Don't forget, I changed the distance to my subject while zooming in.

This is a very powerful tool that is often forgotten, especially with landscape photography. When using an ultra-wide-angle lens, not only a lot of background will appear in the frame, it will also be very small in size. If you shoot nice clouds during sunrise or sunset, with a beautiful subject in the foreground, you may end up with a ridiculous small sun, together with a boring part of the sky. The beautiful clouds will be small and insignificant, and the sun may be only a little speck. By changing focal length, you can change all this, and a larger distance to the subject will keep it the same size in the frame.

You can do this also with fixed focal lenses, but it will take a lot of lens changes and it has less flexibility. In this case a zoom lens will provide a lot of flexibility. It gives a very quick way to manipulate the background in the composition. This technique is possible with a lot of different type of photography. You can use it with portraits, weddings, sports, and of course landscape photography. And you can combine it with a creative depth of field.

Have you ever used this technique to manipulate your background? Or do you have another creative way of using focal lengths to get the result you want. Please let me know in the comment.

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9 Comments

Pierre Dasnoy's picture

No joke ?! :o

Mike Dochterman's picture

"hence the popular statement: “tele-lenses compress distances" - which is exactly what your photos disprove...DISTANCE compresses, not lenses... and yes, I know in real life, one has to get way back to fit the bench in with a tele lens thus it 'works out the same'.. but really..the walking back is the thing giving that look and not the lens

Mike,
there is another factor to consider, and that is from what distance you view the photo.
If you want to experience the same perspective as the photographer did, you have to view the photo under the same angle of view as that of the lens that was used.

So if you don't come close enough to a wide-angle photo, the perspective looks rather strange.
( One can often estimate the focal length used by moving back and forth until the perspective looks natural.)

And if you are too close, to a tele-lens photo, the perspective looks compressed; but if you move back until your angle of view is the same as for that lens, it doesn't look compressed anymore.

It's just that we all prefer to view different photos under the same (personal) angle if view.

Tom Reichner's picture

Mike,

You are absolutely correct. There is no compression caused by telephoto lenses. As you point out, the apparent compression is caused by the photographer's perspective. The same "compression" would exist of any scene from any given perspective, whether it were photographed with a wide angle lens or an 800mm supertelephoto.

Article was good except this one point. I came here to write exactly the same thing about "telephoto lens compression". It is a misnomer, and the main reason new photographers don't manipulate their backgrounds smartly: They think it's the lens, not the subject-camera-background distances. One can get exactly the same close background shooting with an ultra-wideangle lens. You shoot with a telephoto to avoid cropping that would produce low image quality. Please, please, please, banish that misleading term except when explaining it isn't real!

A note on DOF and blur.

Using the above method, i.e. changing distance and zooming to keep the main subject the same size, you might want a rule of thumb for managing the aperture.

1) If you want to keep the sharpness or blur of the (distant) background the same:
> Keep the f-number constant.
This will also keep the DOF around the main subject the same - except that different lenses may render differently.

( If you change to a camera with a different sensor size, change the f-number in proportion to the lenght, or width, of the sensor.)

2) If you want distant bokeh, e.g. distant blurred highlights, to stay proportional in size to the main subject:
> Keep the diameter of the aperture constant - i.e. keep the f-number proportional to the focal length.

( Source: the Lens formula – for those who like math…)
- - * - -

[ On the OTHER hand, if you just stay still and zoom;
To keep the local DOF constant
and the background bokeh
proportional to the background:
> Keep the f-number proportional to the square of the focal length. (Except that different lenses may render differently.)]

Tom Reichner's picture

Have you ever used this technique to manipulate your background? Or do you have another creative way of using focal lengths to get the result you want. Please let me know in the comment.

Nando,

I am always conscious of the relative sizes of all of the elements in my photograph - the relative sizes of the subject, the background, and supporting elements are all considered.

I would like to point out that while the size relationship between subject and background does change, that change is a result of the photographer's perspective - his position - and not the result of the focal length of lens used.

All the focal length does is to help the photographer frame the image by determining what will be included in the photo and what will fall outside of the frame. But focal length does not play any part in the subject size to background size ratio.

Want proof? Put your zoom lens at its shortest focal length, aim at your subject, and shoot. Now adjust that lens to its longest focal length, STAND IN THE SAME PLACE, aim at your subject, and shoot it again. The size of the things in the background will not change at all in relation to the size of the subject.

What you described in your article is called Perspective Control. This is the key to all composition.

Nando Harmsen's picture

"a result of the photographer's perspective - his position - and not the result of the focal length of lens used" I know. But if you don't "zoom in", your subject will become really small in the frame. And yes, you can crop the image to get the same result, but then you will end up with a super-VGA resolution instead of the many millions of pixels we all want.
I want to show how you need to use this in real life, and not a scientific explanation.

John Seigner's picture

Yes , it drives me crazy, lazy photographers often use the zoom to frame their photographs and ignore perspective instead of using their feet to frame the subject and selecting the right perspective. Such a powerful tool.