Wednesday, 20 March 2013

Tele lenses and perspective

One can often hear phrases like "tele lenses can be used to compress the perspective, and make things that are far apart appear close". But it is true?

As the statement it written, it is wrong. A simple geometric argument shows that the perspective only depends on the distance from the camera to the subject, regardless of the field of view, regardless of the lens.



But why believe a geometric argument? We can look for ourselves at a real life example. This image was taken with the Lumix G 100-300mm lens at 300mm:



In the image, it looks like the construction cranes are just behind the neon "Freia" logo on the front rooftop. But in reality, the distance is 1 km. This is what we normally call a compressed perspective.

But is it the long focal length which produces the compressed perspective, as the statement initiating this article? We can see for ourselves, by setting the lens to 100mm, and photographing from the same point. That gives this image:



Does this image have a different perspective? We can crop the centre of the 100mm image and compare it with the 300mm image:



We see that the images are exactly identical. There is no difference in the perspective, demonstrating that the perspective only depends on the placement of the camera, not the focal length.

On the other hand, if I change the point from which I am photographing, as well as change the focal length, then I get a totally different perspective, as illustrated:



Here is the same building photographed much closer with the Lumix G 14mm f/2.5, a wide angle lens:



Now, the perspective is not compressed anymore. But was this due to the wide angle lens? No, I would say, it is because I went closer to the subject.

But, it was the wide angle lens which allowed me to go closer to the subject. Just as it was the tele lens which allowed me to go far away from the subject, to create a compressed perspective.

So while it is not true to say that a tele lens compresses the perspective, it is true that the tele lens allows you to step further from the subject, to achieve a compressed perspective. So, at the end of the day, it is perhaps not so wrong to say that the tele lens compresses the perspective, as this is what you achieve when using the lens anyway.

Conclusion


Having some focal length range available, either as a superzoom lens, or as some different prime lenses, is useful. It allows you to achieve various perspectives, by varying the distance to the subject.



4 comments:

  1. The red bus looks closer on 100mm photo than on 300mm. Must be because wider FL doesn't compress perspective that much.

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  2. The red bus looks closer because it is closer. It is moving towards the photographer

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  3. Firstly, how is it possible to have a discussion on perspective and leave out the 'subject' to background relationship?

    What is your subject in this photo?

    Telephoto compression causes the background to appear closer to the subject when you increase the focal length of the lens.

    I ask, what is your subject in the picture(s)?

    All you a doing here is comparing two cropped backgrounds. The phenomena of compressed perspective is the apparent compression in the distance between the 'subject' & background.

    The building & crane are too far away from the lens to have a subject background relationship. They're both part of the background.

    Quite frankly, once you cropped the 100mm background, you went down the road of confusing yourself.

    Compare side-by-side the pictures (un-cropped) and notice:
    1. the difference in perspective of the entire picture,
    2. the compression between the 'Friea' sign and building (background).

    Cropping an image eliminates the original perspective.

    Please accept what artists many years ago observed theorised.

    Too many ETC crop test lately?

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