Focal length of the lens

Focal length of the lens Is one of the most important lens parameters. The focal length of a lens indicates how far or close (wide) the lens can 'see'.

Focal length of the lens

Focal length of lenses - article from Radozhiva

Focal length is measured in millimeters, centimeters and meters. For example, the designation of the fixed lens Nikon 85mm F / 1.8D AF Nikkor says that his focal length is fixed and is 85 millimeters. A designation Tamron 28-200mm 1: 3.8-5.6 Macro AF Aspherical XR (IF) A03 suggests that the focal length of the lens can vary from 28 millimeters to 200 millimeters. Lenses in which the focal length can vary are called zoom lens (zoom lens, zoom lens). Zoom ratio is calculatedI am dividing a larger number by a smaller one, in this example 200mm \ 28mm = 7 times.

Usually, the larger the focal length of the lens, the larger the size of the lens itself, especially its length.

Focal length Is the first thing to look for when choosing a lens. It shows what angle of view the camera will capture when working with one or another lens.

Attention: the focal length of the lens is the physical size of the lens itself, it does not change and does not depend on the type of cameraon which the lens is used. But for cropped cameras and for cameras with different physical matrix sizes, the parameter EGF (Equivalent focal length), it shows the real viewing angle for a 35mm film, which is obtained when using one lens or another on cameras with different matrix sizes. More details in the section crop factor.

Here is an example of how the space that the camera can cover when using lenses with different focal lengths changes.

17mm

Focal Length 17mm

Focal Length 17mm

24mm

Focal Length 24mm

Focal Length 24mm

35mm

Focal Length 35mm

Focal Length 35mm

50mm

Focal Length 50mm

Focal Length 50mm

70mm

Focal Length 70mm

Focal Length 70mm

85mm

Focal Length 85mm

Focal Length 85mm

100mm

Focal Length 100mm

Focal Length 100mm

135mm

Focal Length 135mm

Focal Length 135mm

200mm

Focal Length 200mm

Focal Length 200mm

300mm

Focal Length 300mm

Focal Length 300mm

For examples, I used a camera Nikon D200mounted on a tripod. All photos were taken at F / 5.6, the following lenses were used:

It is often said that the photographer should have a set of lenses that covers the desired range of focal lengths and thus covers all possible situations in the work of the photographer. One of the most classic sets for full-frame cameras can be considered: 14-24mm, 24-70mm, 70-200mm, 200-400mm. For cropped cameras, usually a good set consists of 11-16mm, 16-50mm, 50-135mm lenses. Covering the entire range of focal lengths is not worth chasing; you can safely do without a single fixed lens. The division into different types of lenses can be found here.

In addition to the angle (field) of view, the focal length affects the perspective of the image (due to the difference in distance to the subject with equal proportions of the subject). At different focal lengths, the sizes of objects are correlated differently in photographs. Long-focus lenses bring closer not only the subject itself, but also the entire space behind the subject and in front of the focus subject. And wide-angle lenses average the sizes of all elements in photographs. Also, different focal lengths affect to blur the background.

17 mm

Aspect ratio at 17mm

Aspect ratio at 17mm

24 mm

Aspect ratio at 24mm

Aspect ratio at 24mm

35 mm

Aspect ratio at 35mm

Aspect ratio at 35mm

50 mm

Aspect ratio at 50mm

Aspect ratio at 50mm

70 mm

Aspect ratio at 70 mm

Aspect ratio at 70 mm

85 mm

Aspect ratio at 85 mm

Aspect ratio at 85 mm

100 mm

Aspect ratio at 100 mm

Aspect ratio at 100 mm

135 mm

Aspect ratio at 135 mm

Aspect ratio at 135 mm

200mm (195)

Aspect ratio at 195 mm

Aspect ratio at 195 mm

300 mm

Aspect ratio at 300 mm

Aspect ratio at 300 mm

Personal experience:

I do not like to convert the focal length from millimeters to degrees of field of view, who is interested, then there is an article on Radozhiv 'Relationship between focal length, viewing angle, and focus distance'. In practice, it is enough to understand what the approximate angles are given by a lens with a certain focal length in order to intuitively know how another longer or wider lens will behave on the camera. Advise experiment with the lens simulator. There is still an interesting article about dependence of the focal length of the lens on the focusing distance.

Conclusions:

The choice of a lens, first of all, entails determining the desired focal length range. Focal length indicates how wide or narrow the lens 'sees'. Focal length is very important to the blur zone of the blur zone and perspective images.

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Material prepared Arkady Shapoval... Look for me on Youtube | Facebook | Instagram | Twitter | Telegram.

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Comments: 122, on the topic: Focal length of the lens

  • Alexander

    I apologize!!!!!! I have a Canon EOS 650D

  • Alexander

    Are there any articles (yours) about Canon?

  • Lydia Shapoval

    Hello Arkady! I'm also interested in Canon D 550, I would like to buy the right lens for it for landscapes, portraits. Macro photography is of little interest, because There is a macro lens, but it does not have an approximation at all - a distance. What do you advise?

  • Vladimir

    Good evening to all amateurs and pros! The third day I have been browsing the forum, my head is just spinning ... Actually, I have a dilemma with choosing a camera. Subjects of shooting: landscapes, portraits, parties, etc. Please recommend a camera and a lens, or a camera complete with a lens. The budget is about 25000. And if possible, a short comment on this or that camera. Thank you in advance ...

  • Dmitriy

    So what exactly is the focal length? Is this the distance between the lenses? The distance between the matrix and the rear lens? Lens size?

    • Arkady Shapoval

      Physically, it is the back focal length, that is, the distance from the back plane to the collection point of the rays (back focus). It is sometimes very difficult to actually show it in the lens.

      • Dmitriy

        Clear. Thanks for the answer!

  • R'RёS,R ° F "RёR№

    Arkady. It’s stupid to ask, or I’ve misunderstood something. Is it possible to find out what the viewing angle will be when increasing or decreasing the focal length. Or they don’t calculate it and look at the lenses. I just want to take the lens knowing what it will give and how it will lead in one or another situation !!!

  • Denis

    Excellent article, everything is told in an accessible language for the amateur! Thanks!

  • Ilya

    Arkady
    Buy the first DSLR.
    Pentax K-3
    Advise lens
    Mostly for shooting children and family. Sharpness and color are important. Well, as the most versatile.

    Pentax SMC DA * 55mm f1.4 SDM
    Pentax SMC DA 50-135mm f / 2.8 ED (IF) SDM
    Pentax SMC FA 31mm f / 1.8 AL Limited

  • Egor

    Arkady, your advice is very necessary. I have a Nikon D3100 Kit 18-55 VR, you need to take pictures from a decent distance
    which is better to choose a lens:
    1) Nikon 55-200mm f / 4-5.6G AF-S DX VR IF-ED Zoom-Nikkor
    2) Nikon 55-300mm f / 4.5-5.6G ED DX VR AF-S Nikkor

  • Evgen

    Good day. Maybe tell me what is better to take (for a beginner). Or advise something.
    Nikon D5100 Kit 18-105mm VR
    Nikon D5200 Kit 18-105mm VR

  • Maria

    Good day. Can you tell me, I have a whale lens 18-135 STM, a Canon 70D camera, I am 70% satisfied with the pictures, do I need a Canon 40 mm 2,8? will he improve my photos? I rent a family, children.

  • Michael

    I will show the article to my daughter, let her learn how to take pictures

  • Yuliya

    Thanks a lot! I searched the Internet for a long time, nothing like that. So simple and affordable! I wish you success!!

  • Andrei

    Many thanks to the creator of this site))) Everything is accessible and understandable) now what interests me immediately on this site))

  • Alexander

    For the first time on your pages and I want to say, everything is simple and intelligible !!! I will visit more often. very interesting and informative.

  • Andrii

    I’m fixing to take a photograph. Your statt is a dude of povchalnі. Crazy.

  • Irina

    Hello ! I want to buy a camera, but I don’t know which one is better Nikon 510018-105 or Nikon 5200 18-55. The main pictures are children and take pictures in the house and on the street. Tell me which camera is better. Thanks.

    • anonym

      the first.

  • VITALIA

    “For cropped cameras, usually a good set consists of 11-16mm, 16-50mm, 50-135mm lenses.”
    tell me what Soviet lenses fit these distances?

    • anonym

      Take the Soviet lens. Look at him. If its focal length, which is always indicated on the frame, is more than 11mm and less than 135mm, then it fits THESE distances.

  • Novel

    Please tell me this moment. Lenses for FX cameras are said to zoom in on crop cameras. That is, for example, we have the carcass D5100 kit 18-55mm f / 3.5-5.6G AF-S VR DX and Nikon 50mm f / 1.4 G AF-S Nikkor. By the method of shooting on a whale, I achieved 50 mm., I shot it from a tripod, I also took a picture with a "fifty-fifty" from the same distance - no difference! How to understand this statement? Sorry if off topic.

    • anonym

      It’s not nador to understand it - it’s some kind of crap. On one camera, lenses from a full frame, from a crop have the same angle of view at the same focal lengths

  • bypass

    NICON D200 has a crop factor of 1.5

    The author mentioned the existence of EGF (equivalent focal length), but he nonchalantly indicated the focal length in the pictures directly from the lens marking without having recalculated.

    I just wrote this.

    • anonym

      and what?

    • Lynx

      On the bosoms always indicate the focal

    • Pastor

      This is the norm! :) It just so happened that the recount is not carried out anywhere. Otherwise, it would be necessary to recalculate the focal lengths for the canon and nikon crops in different ways (they have different crops), recalculate for the micros by 2 times, and for the medium format, reduce them to bring them to ff But somehow the world photo group decided to write real focal points, and bring them on air independently. By the way, on the market, for example, both indicators go to a number of soap dishes - focal and ether, which is very convenient. But for cropped lenses this is not the case.

      • bypass

        Of course the norm. If the article was a review of NICON D200, I wouldn't say a word, everyone will calculate the EFR by themselves.
        But the article on the focal length as such, and I was somewhat confused by the lack of (relevant here) recount.
        Good angle to all. I went.

  • в

    Arkady, survive the apocalypse. Do your job, how well you do!

    • Denis

      survive the apocalypse only moisture-proof

  • Igor

    Arkady, do not mislead the newcomers. Focal length does not affect the perspective! The perspective is affected by the distance to the subject.

    • Arkady Shapoval

      Fixed Added explanations in brackets.

    • Valentine

      The prospect directly depends on the focus.

  • Alexandre

    Health to all! In the M mode, in the “lens without kpu” menu, what value of the focal length on the Nikon d200 should be indicated, actual or taking into account the crop factor? For example, Jupiter 37a?

    • Valery A.

      Actual, 135.

  • Ivan

    Tell me please!
    I have an 85mm ff lens. I use it with a dx camera. For example, I shoot a portrait from a distance of 4 meters. At what distance should I be in order to get the same frame if I use the same lens, but with a ff camera?
    I will be very grateful for the answer!

    • Alexey Shch

      3 meters

  • Zoom zoom

    so, once again ... do I understand the article correctly ?! If I have 18-105, then the zoom factor is 5,83 and my 55-300 has a zoom factor of 5,45. So, if I shoot at 55-300, then in relation to 18mm I will get a multiplicity of 16x? What am I asking ?!: I used to have a camera with an 18x zoom, I'm trying to figure out which lens I need to get that kind of zoom (close to 18x) ?!

    • Arkady Shapoval

      Zoom is only a multiplicity between the extreme positions. It is obtained by dividing the maximum focal length to the minimum. And no one knows what the minimum or maximum you had, because there is no 18x to apply to. But, most likely, you had something in the EGF area of ​​24-400 mm. DSLR cameras have practically no such lenses. The largest zoom lens currently available for SLR cameras is Tamron 18-400 from 22X.

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