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
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 :)
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I have such an effect on Helios 81H, but on nikon 18 - 105 without saying anything.
I do it a year before reading the stats and the notes for 18-105. It’s wonderful, ale tse at least once again, if I’m helping, but then I’ll get a look here :)
Owners of Tair 11A, I think this article has indeed been met in life ... since the lens has a feature at focus from 1.2 to 2.5 (from copy to copy), there is an increase in focal length from 133 (135) to 230-250mm focal length !!! this effect can be used for your creative ideas)
Arkady, tell me, what difference does it make if the focus lens is marked with the same focal length? For example max. I saw at 85 mm it goes on one 4m, on the other 10, 15. 17 and then infinity, so what's the difference?
The difference is in the focusing step, I indicate in the reviews, for example, that the focus ring rotates a certain number of degrees, while the lens has its own step for changing the distance. For some lenses, the step is large (for focusing from 15m to 4m you need to rotate the ring for a long time), and for others, the step is small (shifting the focus ring instantly throws from 15m to infinity, etc.). Therefore, even physically it will not be possible to indicate intermediate values on indicators. Also, each lens has its own hyperfocal distance.
this is due to the thread design of the focusing lens. I have 70-210 on the sigma, for example, the stroke is less than 90 degrees, on the manuals, about 360, which is very inconvenient. I don’t remember on a whale, like 180. I took apart the whale, there the thread is at a bad angle, not like on a helios for example. In addition, whale 18-55 focuses differently, because the zoom.
In principle, I did not pay attention to this, but if it is realistic, for example, on the Helios 44, the lens block is solid and extends 1 cm when focusing, then we must assume that the focal and angle will change. As for the aperture, you seem wrong. Well, TTL will recount, but the old cameras were not TTLs and still shot correctly, and I never heard of that. Moreover, there are type L lenses with internal focusing. They can be compensated for offset focal and angle. Again, if you say that the diaphragm shifts so sharply at focus, what about lenses like 28-300 2.8 L? if there is a constant aperture at SUCH zoom, I doubt that something will change when focusing.
Yes, by the way, maybe there is such a glass at the box office, it is very expensive, I would like to know your opinion about such a lens.
The 28-300 2.8 L lens does not exist. When working with ordinary lenses, the effect, as I wrote in the article, gives drops no more than 1 \ 3 steps, which is not always critical. If you still take expensive zoom lenses of class 70-200 2.8, then they have this effect, I know for 70-200 2.8 nikon VRI
Yes, I was mistaken 2.8 maybe only 70-200.
If I honestly did not even think about such a topic, I tried it with all the lenses, but the angle changes. This is directly related to the formula doubled artangent multiplied by the dioganal of the matrix divided by twice the focal length.
Plus for information
In your Nikon 70-210mm f / 4 AF review you wrote: “The lens has a constant aperture ratio. This means that whatever one may do, the zoom is from 70 to 210, and the aperture ratio will be constant. " And why doesn't its aperture change?
The lenses are probably big and bright. worth looking at the price ...
The maximum aperture ratio remains unchanged when zooming due to the lens design.
Victor, some zooms use something like a “second aperture” - when zooming, its diameter changes in proportion to the displacement of the lens group and the ratio of the front pupil to the focal pupil (which determines the lens aperture) remains really constant. Or they put a tricky three-component front element, in which the diameter of the front component changes in the same way in proportion to the zoom.
Arkady, you never cease to amaze! How many articles have already read, and you always have something new. Thank you very much!
It's my pleasure :)
please tell me how to make a blurred background on samsung wb150f
First you need to sell it. Buy a reflex camera. Read the blog and shoot.
But seriously, first of all, shoot on an open aperture and broadcast from about 150 on your camera.
but please in more detail !!!!
Shot with a blurred background is very difficult on your camera.
https://radojuva.com.ua/2012/01/dof-best-lens-photo/
it’s difficult to get a blurry background on your camera
https://radojuva.com.ua/2012/01/dof-best-lens-photo/
Thanks !! Tell me more how to shoot on it in macro photography ????
У
Your camera should have an automatic macro mode.
Hello Arkady. An interesting article, and now such thoughts arose, I do not know whether they are correct or not. As I understand it, in your article, focusing at infinity is the HH (hyperfocal distance) of the lens at a given focal length and aperture. Then you can use the effect described above to determine the HH at the given parameters, if you point the lens at the sky and turn the focus ring towards the closer until the shutter speed value in mode A changes. After all, as I understand it, does this effect take place when focusing from GR to MDF, or only on MDF?
GR is not quite at work here.
Hello,
I am a D7000 user, and I suspect the camera has a slight back focus. I’m going to shoot at targets a few days ago and make corrections in the camera, but I heard that you can pass them to a service center in Kiev. The question is, in fact, which is preferable? Is the technology for adjusting the SC different from ordinary shooting at targets at home? Is the adjustment done by the camera + lens or separately the carcass at 0 and the lens at 0?
Service does differently. Adjusts the lens in conjunction with the camera.
Not aperture, but aperture ratio. Since it is relative, when the focal length changes, it also changes proportionally. This is how it is written on lenses - “f / 2”, for example. And the focal length is indicated when focusing at infinity.
And no “equations” are needed. To obtain a macro scale of 1: 1, the lens extends to its own focal length, so, for example, 50mm turns into 100mm, and f / 2, respectively, into f / 4. But this is true only for lenses with focusing by moving the entire lens unit. For lenses with internal focusing or focusing by the front lens, as the focusing distance decreases, the focal length also decreases (!). For example, if such a lens, when focusing at infinity, has a FF of 50mm, then with a focusing distance of 0.5m, its focal length will be about 45mm.
Actually, the article is called "the dependence of the relative aperture ...".
The diaphragm is inversely proportional to the relative aperture. therefore connected with it directly
For example, a relative aperture of 1: 8 is aperture 8
Otherwise, I completely agree: a double focal length is 1: 1 macro photography. and the focal length is the distance when focusing at "infinity"
When changing the zoom, the aperture changes to Nikon D90. In all modes! Is there any way to stop these auto tuning!? Zadolbalo it already! At least zenith fly with Helius again
You can’t, you have a zoom lens with a variable aperture.
Hello, Arkady.
I have a Panasonic Lumix DMC-GF3 camera, its lens is H-HO14. The instructions say that focusing with this lens is impossible, but the focusing ring is there and rotates ...
I am just mastering the camera and trying to figure it out. Please tell me what is the focus ring for?
Regards, Vasilisa.
Hello Arkady! please tell me: i bought a nikon 55-200mm lens. with the exposed fr 200mm real fr for some reason 125mm. this is normal? I suspect not))) and I think this is not what you wrote about in the article ... and another question, if you have experience with this glass, tell me it's normal that autofocus for this lens works only during the day, only on the street and only in sunny weather ??? Well this is chaos))))) An old whale with the same aperture shoots with much less illumination. Thank you so much!)_)
Hello, please help me sort it out ...
I have a Nikon D5100, a whale lens 18-55,
everything was fine and worked until I touched the lens (the camera was turned on) ...
although it didn’t hurt much, but now when you press the shutter button to focus, it doesn’t work and you have to turn it on the lens manually so that the focus works ...
maybe something broke there?
I read in the settings but there is nothing .. I thought maybe clicked somewhere but there is nothing in the settings to fix it ...
what to do? carry in the repair? can you advise?
Turn on autofocus
Good day! Please tell me, on a Nikon D7000 camera with an 18-105 lens in LV mode, when you change the zoom, the aperture changes, in any of the shooting modes !?
Even if the diaphragm was originally at 5.6 ...
For example, at zoom 18, the aperture is 5.6, and when the zoom is increased to 105, the aperture increases to 9
Until this moment, this was not, I really need your help!
the aperture changes with the change in focal length, that is, zoom. the law of nature however ...
This is true only for lenses with variable aperture. There are so many zoom lenses that may not change the aperture value, for example Tamron AF 17-50mm f / 2.8 XR Di II LD Aspherical (IF). When you change the focal length, the aperture may remain constant F / 2.8.
Hello. There is a question, I would be glad to know your opinion on this matter. Let's say I set the aperture to f / 18 / on the zoom lens at a focal length of 11mm. hence the diameter of the diaphragm itself = 18mm / 11 = 1.6363636mm. when the focal length is increased to, say, 110mm, without changing the relative aperture (F / 11), the aperture diameter = 110mm / 11 = 10mm. It turns out that the diameter of the diaphragm is reduced by about 6.1 times. does the exposure change because of this? because less aperture means less light. it is rather difficult to verify this assumption in ordinary terms. I tried this: I used spot metering in A. at 18 mm it was 1 / 6sec, and at 135mm it was 1/8. So my actual question is, shouldn't the relative aperture (Aperture ratio) mean exactly the amount of light passing through the lens, or is it just a relative value that depends on the focal length. I apologize for not quite correct wording.
What's the question? The aperture did not change, but the diameter increased.
Not a diaphragm, but a hole (diameter).
"The focal length indicated on the lens is valid only when the lens is focused at infinity."
Focal length, by definition, is the distance from the focal plane to the main optical plane with the incoming parallel beam of rays. For a single-lens lens, the focal length is a constant that does not depend on focus in any way. Do not confuse focal length with the distance from the image to the main optical plane, which varies in proportion to the distance to the object.
In an ideal centered optical system, consisting of an arbitrary number of coaxially arranged lenses, the front and rear main optical planes are distinguished, respectively, the front and rear focal distances. It is the rear focal length that is the main characteristic of the photo lens, and it does not depend on the aperture.
If a multi-lens lens is focused by the simultaneous displacement of the entire lens unit (the so-called “total linear elongation”), then its focal length is strictly constant.
If focusing is carried out by moving only part of the lenses (front focusing or linear lengthening of the front group, internal focusing, rear focusing), then the focal length, depending on the lens design, can vary within small limits - and not the fact that it is linear. But not to change at times. And even these variations in focal length have nothing to do with aperture.
If you do not believe the word, read the textbooks on geometric optics. Discover a lot of interesting things.
Article updated. Thank you for your attention.
Hello! There is such a macro method when two or more pictures taken with focus on different edges of the object (far and near) are combined. I tried so to remove the ring on Nikkor 105 2.8 BP, and could not, because with refocusing, the scale of the ring changed significantly. Maybe you know the lenses rid of this problem?
This is called a stack shot. You do not have to refocus, focus on the manual and move either the object to the camera or the camera to the object. It is advisable to maintain the same shear distance.
this feature is already in the new firmware for mirrorless Olympus. called
Focus bracketing mode
they have a function for macro shooting auto refocusing followed by gluing.
in detail
http://dmitry-novak.livejournal.com/216184.html
I have a Nikon D90, with a Nikkor AF-S 18-105 ED vr lens, I have been shooting portraits on the SigmaEF6 / 70EX portrait lens for 2.8 years, now I am planning to update my "arsenal", to buy additional Nikkor AF-S35 / 1.8DX or 50 / .1,8G., Now I am tormented in choosing between these glasses, after reading an article on these glasses ... I like the bokeh of the 35 / 1,8DX, but I would like to use it (35 / 1,8) for portrait photography as well, as you think. Shapoval, I would like to hear your comment ..