Dependence of the viewing angle of the lens on the focusing distance

When focusing on some lenses, a very interesting effect can be noticed. Many lenses change (usually reduce) the angle of view when focusing from infinity to MDF (minimum focusing distance). In Western literature, this effect is called 'Focus Breathing'.

Dependence of the viewing angle of the lens on the focusing distance

Dependence of the viewing angle of the lens on the focusing distance

This can be easily checked, it is enough to turn off the automatic focus on the lens and focus on anything from infinity to MDF, while you can notice that the frame borders expand and contract, and there is nothing to blur the borders of.

Lenses that give the same viewing angle when focusing on infinity can give different viewing angles when focusing on MDF. Here is an example with three class 85 / 1,8 lenses. Everything is taken from a tripod from the same focusing distance.

This effect is very highly visible when working with macro lenses that change the maximum aperture value depending on the focusing distance. For example, you can read about it in the review of macro lenses. Nikon 105mm f / 2.8D AF Micro-Nikkor и Tamron SP AF 90mm 1: 2.8 Di MACRO 1: 1 272E for Nikon. For a simple understanding, we can say that with focusing lens makes easy zoom. This also applies to fixed lenses and zoom lenses. Visually easy to understand the effect of the example of a fixed lens Tamron SP AF 90mm 1: 2.8 Di MACRO 1: 1, in which the trunk lengthens when focusing in macro mode, as if the lens were zooming, and at the same time the field of view changes.

Personal experience

Changes in the field of view when focusing is sometimes very unnerving, as it leads to the fact that parts of the desired composition fall out of the frame, and you have to move in or out of the subject. When I shoot macro, this effect is especially felt. Visually, it seems that the focal length of the lens is changing, while they say that the lens changes its focal length - this is not entirely true. Focal length is measured when focusing at infinityb, when the rays go parallel to the optical axis, but when focusing toward the MDF, it is no longer possible to speak of the focal length as such.

conclusions

The effect described above is not always noticeable in practice and you should not worry too much about this. What is 'Focus Breathing' is well known to videographers, who are much more annoyed by this effect than photographers :)

Help to the project. Thanks for attention. Arkady Shapoval.

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Comments: 54, on the topic: Dependence of the viewing angle of the lens on the focusing distance

  • Nicholas

    if the focal length 135mm is written on the lens, then it will be 135mm on the crop and on the plane !!! only the angle changes, the crop cuts the frame in view of reducing the size of the matrix and visually it seems that the lens is moving closer, the focal length never changes to which camera you put it on.

  • Masha

    Just this effect made me almost turn gray!
    I took test shots from 18-105 and from 70-300 (on focal lengths 70 and 105) I got 4 completely different shots !!! Indeed, as if the focal length is changing. I already thought that the DX 18-105 was immediately indicated by the equivalent focal length, but in time I realized that Focus breathing was to blame for everything.

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English-version of this article https://radojuva.com/en/2013/01/interesting-about-f-number-and-focal-length/