The diaphragm is simple. In a nutshell, aperture is a device in the lens that measures the amount of light.
For a better understanding of the operation of such a device, I will give an example from life. When people look at the sun, they squint their eyes, that is, they reduce the gap through which light passes. If people did not squint, the sun would burn the retina with its strong light. At night, you need to do the opposite - open your eyes wider to capture more light, while the pupils also dilate. Eyes with large pupils have many animals that need to see well at night.
Often the diaphragm is also called 'luminous efficiency ' or 'aperture' or 'relative hole' or 'number F'. These concepts are strongly related to each other and are synonymous for many photographers. But among them there are small differences, described below.
Lens aperture Is the ratio of the effective aperture of the lens to the focal length of the lens. The reciprocal of the relative aperture is called f-number or aperture number.
The relative aperture of the lens is expressed numerically by ratio or fraction. For example, take a lens that has a relative aperture 16 times smaller than its focal length; as a result, the relative aperture can be numerically written in the following ways: 1:16 or f1 / 16 or f = 1: 16 or F 1:16, etc. d. There is no particular difference in the recording, and every photographer will always understand what is at stake.
If we take the number opposite to the relative aperture, then we get the number of aperture. Usually it is by this number that photographers directly understand the general term 'aperture'... If we take the same lens, which has a relative aperture 16 times smaller than its focal length, then its aperture number will be equal to 16. And numerically it can be written in the following ways: F16, F / 16, 16 (such a 'bare' number aperture is indicated on the lens barrel). There is no particular difference in recording.
Some lenses have an aperture ring on their body. There is usually a marking on the ring, consisting solely of aperture numbers (shown in the figure below). Almost all modern lenses do not have such a ring, and the diaphragm is controlled by the electronics and camera controls.
Usually the concept of 'aperture' and 'aperture' are synonymous, but in fact there is a certain sacristy between them. So, the diaphragm is only responsible for geometric aperture (the ratio of linear geometric indicators). And not only the aperture is responsible for the overall 'real aperture' of the lens, but also many other factors: the optical design of the lens, the percentage of light reflection and transmission by the lens, the drop in the aperture number when focusing at different distances, the percentage of light absorption by the photo filter, etc. More details about the difference between the concepts of 'aperture' and 'aperture' can be found in the section about 'T-feet'.
The aperture is sometimes also called the 'Lens Aperture' (Latin 'Apertura' - 'Hole'). Therefore, on many cameras, the metering mode exposure с aperture priority called 'A' or 'AV'-'Aperture Value '-' Aperture Value '. Details about this mode are described in the section 'P, A (AV), S (TV), M'.
Please note that the magnitude of the front lens of the lens and, in fact, the magnitude of the front light filter have no direct relation to the aperture ratio of the lens. Different lenses with the same focal length and the same maximum aperture can have completely different diameters for their front lenses. For example, take two class 50 mm F / 1.4 lenses: Nikon AF Nikkor 50mm 1: 1.4D и Sigma 50mm 1: 1.4 DG HSM EX... The first has a tiny filter diameter - 52 mm, the second has a huge one - 77 mm. But their aperture (practically - maximum aperture) will be the same.
What is the diaphragm?
By the mechanical part of the diaphragm device is understood a changing circular hole in the lens. Typically, the hole opens and closes with the petals. In this case, the petals are called diaphragm blades, and the diaphragm itself is 'iris' (from the English 'iris' - 'iris'). The number and roundness of the aperture blades determines how much the hole will be formed round. The stronger the rounding of the diaphragm opening, the better. Professionals often refer to the diaphragm simply as'hole'since it is real, a kind of hole that changes its size and doses the amount of light.
What the diaphragm affects:
- The amount of light that the lens can let through over time.
- To control the depth of sharply depicted space (GRIP)
- The brightness of the image in the optical viewfinder
- On image quality, especially on its sharpness, aberration, vignetting, bokeh and various visual effects.
IMF impact
As it turned out, the aperture affects not only the amount of light, but also the depth of field. The smaller the number F, the smaller the depth of field. The larger the F number, the greater the depth of field. This is one of the main techniques in photography to control the point of attention in the photo. It is very important to be able to manage GRIP for portraits where you need to focus on a person. Macro photographers are well aware what is DOF, they have to shoot on very tightly closed apertures to increase the depth of field. In general, where write about DOFwrite about blurred background. You can read the best way to take pictures with a blurry background in my article - Taking Pictures with Blurred Background.
Depth of field preview
Typically, modern cameras have the ability to focus with a fully open aperture. When a picture is taken, the camera’s automation closes the iris to the set value. To see how the images will look when the aperture is closed, you can sometimes use the aperture repeater. This allows you to look into the viewfinder (optical or electronic) without a picture how the picture will look when the camera closes the iris. You can read more about depth of field preview.
Aperture for picture enhancement
Aperture is understood to mean simply changing the aperture value. Using aperture control, you can achieve a sharper image from the lens. Basically, the sharpest image is achieved somewhere at the average aperture of a lens. At their largest aperture, lenses suffer from chromatic aberrations and vignetting. When closing the diaphragm HA and vignetting practically disappears. At very small apertures, lenses suffer from diffraction loss of sharpness. Also, when you close (decrease the aperture), not only the sharpness increases, but also the contrast of the picture. A large aperture allows sighting through the optical viewfinder without any problems, since the lens gives a lot of light and the entire frame is clearly visible through the peephole. You can only view with an aperture below F5.6 through the optical viewfinder in good lighting conditions. Also, pictures with a larger aperture can appear brighter and more saturated - this effect is associated with smoother transitions in pictures from dark to light areas.
Bokeh and aperture connected forever
Aperture greatly affects the bokeh pattern. Usually the best bokeh for the lens is achieved at the maximum open aperture. In this case, the physical hole itself is as round as possible. When closing the diaphragm, the diaphragm petals instead of a circle form different polyhedrons. These polyhedra are clearly visible in the blur zone. Very often such polyhedra are called nuts, washers and circular saws.
Since in cheap lenses there is a small number of aperture blades, usually no more than 5-6, then in the blur zone figures appear exactly like “nuts”. Those lenses that on closed apertures give the correct round luminous spots in the blur zone, for example, can be attributed to them. Nikon AF DC-Nikkor 105mm 1: 2 D Defocus Image Control or Tair-11A 2,8 / 135. In new lenses, it is very rare to find a large number of aperture blades, but now they make more rounded blades, which, even with a small number of them, give a round hole.
Below are my photographs taken with different cameras and lenses and taken at different values of the number F. Shooting options (EXIF) for each photo are indicated in the bottom line.
Aperture in phone cameras and other small devices
The diaphragm is a mechanical part of the lens, it cannot be done programmatically. Almost all phones lack a physical diaphragm device. Many 'soap dishes' also lack a diaphragm. How to be? Usually the camera in such devices doses the amount of light only shutter speed and a variation of the ISO value, and the aperture value itself is constantly fixed at the maximum value. For example, on my Nokia 7610 it is indicated that F2.8, because the camera always shoots at F2.8.
How to adjust the aperture in the camera?
In cameras, it is responsible for the diaphragm F number (aperture number)... It shows how many times the diameter of the relative aperture is less than the focal length of the lens, on the lens it is written as f1 / 1.4 or f1 / 5.6, sometimes you can find the spelling f = 1: 6.3 or 1: 5.6, or f / 16, f / 3.2. Often, lenses or cameras only have one f-number, such as' 1.4 'or '16.0 .8.0'. Usually, the aperture number is written with a large letter 'F' without fractions, for example, F 1, and the relative aperture is more often written through a small letter 'f', for example f 11:XNUMX (there can be any spellings). The easiest way to adjust the aperture is by putting the camera in aperture priority mode. On the main control wheel of the camera, or in the menu of the camera, this mode is indicated by 'A' or 'AV'. To make it easy to remember, you can simply say: Aperture means you need to turn on the 'A' mode. Details about the creative aperture priority mode are written here.
'Light' and 'dark', 'fast' and 'slow' lenses
The maximum aperture value determines how much the lens can be used in poor lighting conditions. Lenses with a large aperture are called 'bright' or 'bright', usually an F value should be below 2.8. That is, lenses with maximum apertures F1.4, F1.8, F2.0, F2.2, F2.5, F2.8 are called fast or just bright. Everything below F1.4 is called super fast. Super fast lenses include Nikon 50mm f / 1.2 AI-S Nikkor or Canon Lens FD 55mm f / 1.2 SSC. Lenses that have an aperture value of F / 2.8 to F / 5.6 are called ordinary. medium-aperture lenses, these lenses can be attributed Nikon 24-85mm f / 2.8-4DAFIF Nikkor or Nikon 300mm f / 4.5 Nikkor-H Nippon Kogaku Japan Auto Non-AI. Lenses with a maximum aperture less than F / 5.6 are called low-aperture or 'dark'. These lenses include MS MTO-11 1000mm F10.0. By the way, it is very difficult to make a fast zoom, in more detail here.
Since aperture affects speed excerpts, then the lenses are still divided into fast and slow. A fast lens means that you can use it to shoot an image with a short shutter speed (with 'fast' shutter speed). And under slow, that it can be used to take a photo with a long ('slow' shutter speed). If you fix the ISO value, it depends on the aperture excerpt, and the brighter the lens, the faster it is. And the darker the lens, the slower it is.
The difference in aperture ratio
The difference in aperture and other photographic variables is usually measured in feet. When changing the aperture by one stop excerpt will change in twice... Also, if you change the aperture by one stop, you can change the ISO by two instead of the shutter speed. It is very important to note that the difference in aperture values is not linear, but quadratic. Take two apertures F / 5.6 and F / 2.8, it would seem that the difference in geometric aperture is 5.6 / 2.8 = 2 times, but this is not true. On aperture affects the area of the circle formed by the diaphragm, and not its diameter. The number F is associated only with the diameter. To calculate the difference in area you need to take the squares of the diameters. Therefore, it turns out that the difference in aperture ratio between F / 5.6 and F / 2.8 is (5,6 * 5,6) / (2,8 * 2,8) = 4 times. Here is such a trick. How to remember this? There are two ways out, either by dividing the squares of the F numbers, or by first dividing the F numbers and then squaring the result. Why am I bored with calculations - but because often amateur photographers have no idea how many times one lens is 'lighter' or 'darker' than another lens.
Also, experienced photographers know about the so-called aperture series of numbers, in which every two adjacent numbers F differ by one stop.
A number of numbers F: 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 46, etc.
Golden Rule:
Aperture and shutter speed are bound by the golden rule. To keep correct exposure with the same ISO, you must either close the aperture and increase the shutter speed, or, conversely, open the aperture and reduce the shutter speed.
Close, open, increase decrease - no need to be confused
Everything is very simple. Closing or decreasing the aperture means increasing the F number. The aperture was F2.8, when it was closed, it became F5.6, it was closed even stronger, it became F16.0, etc. For example, there is the phrase 'covered the hole by two stops', it is deciphered as follows: 'made the number F large and reduced the area of the hole by 4 times'. The main thing is not to get confused, when the aperture opens, the F number decreases. And when the diaphragm closes, the F-number increases. For example, the aperture was F32.0, when it was opened, it became F8.0, when it was opened even stronger, it became F5.6.
What to do - nothing is clear
If you have a DSLR, turn the camera backwards so that you are looking into the lens, press the shutter button (take a picture) and you will see the hole in the lens close and open - this is how the aperture works. If you peered into your lens and did not see anything, then below is a slow-motion video, where you can clearly see how the aperture works during shooting. In the video, the petals close to F / 16 and form a very 'small hole':
- The method of operation of the device aperture on Nikon digital SLR cameras and its effect on video recording
- Nikon 'E' Lenses with Electromagnetic Iris Control
- An interesting aperture on Nikon digital SLR cameras
- G-type and Non-G type lenses (with aperture ring and without aperture ring)
- Work with old Nikon lenses such as AI, AI-S, NON-AI, PRE-AI, AI-Converted, which transmit or do not transmit aperture value to the camera
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Conclusions
Diaphragm Is a luminous flux dispenser that affects exposure, GRIP, brightness of the optical viewfinder and image quality. In general, if you don’t shoot at different values of the number F, you don’t really know what it is :)
Material prepared Arkady Shapoval.
There was no lens with a constant aperture at hand.
The change seen in the zoom of 70-300 mm did not give a complete answer to the question (although visually the hole becomes larger). Probably have to buy a zoom with a constant aperture and disassemble it)))
Arkady, there is still a question partly on the topic. They offer a lens 70-210 f4 ai-s e-series, but on it a minimum of information on the network (even Uncle Rockwell ignored it). Interested in opinion in general as a lens and how will the aperture on the D7100 work on it?
at 4.0 the aperture is not enough for the 7100, this is a series of cheap “E” lenses, they say that the optical is similar to the 70-210 / 4 AF, with a beautiful pattern. As for the diaphragm - well, since you've seen the hole change with your own eyes, what else do you need?
Thank you for your reply!
It’s just a tempting price, a five plus state, and it’s interesting to try the manual thrombosaurus on a modern camera. Although 70-210 / 4 AF is also a reasonable offer. Apparently a consumer attack has flooded here is something I'm looking for.
Regarding the diaphragm, I still can't get it (apparently the holidays have done an irreversible deal with the brainwave) - because if the diaphragm can be wider at the long end, then there will be a limiter on the short end so that it does not open (which is not good).
During the day, you can normally shoot static scenes. But dynamic on a cloudy day is very difficult.
If you put Nikkor on Kiev-19? And how to control the diaphragm?
If the lens has no aperture ring, then nothing.
You can like this https://radojuva.com.ua/2013/12/nikon-reverse-adapter-g-type/
My friend and I had a little argument. Let's say there is a fifty-dollar f / 1,4 fix on a full-frame camera. The aperture was closed, say, to 5,6. And the zoom, let's say 28-300mm f / 3.5-5.6, set at the same 50mm focal length. The aperture is also set to 5,6. The dispute is this - will the physical diaphragm diameter be the same in both cases, or will the diaphragm diameter be smaller at zoom?
The inlet will be the same.
As far as I understand, the diaphragm diameter will change with the change in focal length? That is, the aperture of 5,6 for 100 mm focal length is smaller than the aperture of 5,6 for 18 mm?
For a larger focal length, a larger aperture. It is indicated that this is the ratio of the effective aperture of the lens to the focal length of the lens. The reciprocal of the relative aperture is called the f-number or f-number.
I read it, the material was compiled very competently. Everything is clear and accessible. For me, one of the most valuable statements is that it is necessary when photographing to look for a parallel with the physiology of human perception (like the same observation about bokeh was how the background blur effect manifests itself).
It seems to me that the closer the work is to human perception (for example, in the photo, not the main thing is made less clear, focus on the main thing in the picture), the more positive emotions it will cause.
This does not mean that the classical approaches cannot be violated, the artist can always flaunt the fact that he “sees it this way”. But to be eligible for such courage, of course, you first need to master the classic requirements. As, indeed, in art in general (in painting, in cinema (comfortable editing, the golden ratio in composition, plot), in ballet, etc.).
Good luck and success.
Answer the newcomer if I understand correctly that even with the minimum possible (maximum) aperture value on the camera 3,5, I will not be able to even put the notorious 3,5 in even aperture priority mode for certain ISO values (in dark scenes). It’s just what happens to me when I try to select the optimal ISO values in mode A, does the camera set the maximum threshold (i.e., not 3,5, but 4,8 and 5)? Can this be circumvented and will it make practical sense. Or is it just because of my inability to work with this setting?
Thank you
If you have an 18-55 f / 3,5-5,6 type 'zoom' lens, then the maximum open aperture of 3,5 is possible only at the minimum FR, when 'zooming' the aperture will be 'automatically covered' to the maximum possible value by this FR.
Thanks a lot! I began to understand the issue slowly about the variable and constant aperture. Yes, I have just such a whale zoom.
What is a “working diaphragm”?
working aperture - the one from which the lens meets the image quality requirements, or
working aperture - the one at which the shooting is taking place at the moment.
Thank you.
Arkady, good!
An interesting question: is it possible somehow on nikon lenses without a diaphragm ring (in particular on nikon af-s 35 1.8 to set some aperture value, for example 8 and clearly fix it mechanically through the lever on the lens? Nikon d60 camera.
The question is related to macro photography.
Thanks.
If you don't mind, my answer is, the 35mm 1,8 is not the best lens for a flip-flop. 18-55 is more suitable. You won't be able to fix with the exact value, only with a very, very approximate. You can fix it with matches, pieces of paper and in general with all the junk at hand, small rubber bands, plasticine, a drop of hot glue. Shoot only in manual mode and only with flash.
Hello. Please clarify my head. As an example, we will focus on the Canon 18-55 f3.5-5.6 kit lens. All my life I believed that at the maximum angle of view during shooting with a focal length, for example, 18, the lens takes on an aperture value of 3,5, and at maximum zoom it takes on a value of 5,6. The catch is that with a wide angle the diaphragm should close, and with an increase - open, but here it turns out the other way around? Explanatory please. thanks
re-read the article again and understand the concept - the relativity of the focal to the size of the hole.
Honestly, I did not understand the snag. Why “at a wide angle, the diaphragm should close, and with an increase - open”. How many lenses I know with variable aperture, I have never seen that at a wide angle it was smaller than in telephoto. Always the aperture decreases with increasing focal - the laws of optics. They can be bypassed by making a more expensive and larger lens with a constant aperture.
Just Alexander confuses what is desired with reality. For example, I would also like such a magical lens, you zoomed it, for example, up to 200 mm in the portrait, and he, such, once, opens a hole for you from 5,6 to 1,4. :)))
Yes, it would be just gorgeous. At 18 or 24 mm f5.6, large depth of field and everything is sharp for the landscape, and at 200 mm 1.4 and ears in bokeh :) When this lens is already released, how much can you feed us with all kinds of optical nonsense! :)
If you make aperture number 200 at 1.4 mm, then the aperture should become 200: 1.4 = 142,8 mm. What kind of sensor should it be?
any sensor, at least crop
typo: "but in fact there is a certain sacristy between them"
if I remove the aperture blades on the Nikon AF-S18-135mmf / 3.5-5.6ED-IF DX zoom-nikkor and shoot video in manual mode, will it keep the same aperture? after all, as you know, on the working lens, the aperture closes when zooming, why is this done?
It does not close; the relative aperture changes. That is, the hole size divided by the focal lens.
how it doesn’t close, the picture darkens from 3.5 to 5.6 when zooming
Fuck ... .. Stupid!
Revealing the previous cattle answer: honorable sir, if you please devote 5 minutes to studying the variety of lens designs, and then another 10 - to the school optics course.
Then you will reach Zen and understand why it does not close when zooming, although the relative aperture changes.
As already answered - it does not close. In order to make sure and check, you do not need to remove anything - it is enough to block the diaphragm control lever with something.
it’s just that there is a lens without a pair of petals, and I thought to remove everything so that it always has f3.5 and I don’t need it for video, the main thing is that the zoom should not change when zooming.
it’s just that there is a lens without a pair of petals, and I thought to remove everything so that it always has f3.5 and I don’t need it for video, the main thing is that the zoom should not change when zooming.
Thank you very much! The most interesting, detailed, understandable article, even for a beginner - a girl !! ) in just half an hour I figured out all the moments I did not understand!
“The relative aperture of a lens is a ratio or fraction. For example, let's take a lens that has a relative aperture 16 times smaller than its focal length, as a result, the relative aperture can be numerically written in the following ways: 1:16 or f1 / 16 or f = 1: 16 or F 1:16, etc. etc. There is no special difference in the recording and EVERY PHOTOGRAPHER WILL ALWAYS UNDERSTAND WHAT IS THE SPEAKING ABOUT ”. - Arkady! It is clear that you are not writing an article about aperture for photographers .. You can somehow explain it more easily, relatively newbies read it. Thanks!
There goes a simpler explanation, for example, in the paragraph "What is the diaphragm?"
Good article! Thanks! I also liked the explanations here. http://hobbiphoto.ru/diafragma-obektiva-obyasneniya-dlya-novichkov/ can someone come in handy
Thank you very much Arkady! Your articles are a treasure trove of information, and you are a born Teacher! everything is clear, easy and accessible (stylish, fashionable, youth :))
what beautiful pictures !!!
Thank you very much for the very interesting, informative material.
Dear experienced authors. Tell me.
Here is an approach for those who shoot landscapes - to close the aperture more to obtain greater sharpness throughout the frame.
An example when you try to take pictures at dusk without a tripod. In general, without grease, you can take up to 1 / 5-1 / 3 shutter speed (according to my feelings), respectively, other things being equal (I didn’t take a tripod), it is difficult to set longer than units, since you yourself can not control the process, it will be greased. If you leave the closed aperture at this shutter speed (up to unity), you will have to set it higher. At D800, whatever they say, the noise is felt like my old camera, just to a lesser extent. Instead of noise, I tried to shoot on an open aperture.
Has anyone done this? ) I liked the result, although the picture could have been sharper, probably if I had a tripod and the ability to increase shutter speed and cover the aperture.
Firstly, the landscape still implies a tripod and low ISO) But if you really want to ... The camera has a certain sensitivity limit, above which the image degrades and it will not work to suppress noise without losing detail. So first we raise the ISO to an acceptable level, if not enough - open the aperture, shutter speed at the limit. Secondly, the aperture is closed not only (and not so much) to improve sharpness, but to increase the depth of field. If there is no foreground in the frame or you have super-width, then you can shoot in the open)
Thank you!
Thanks again)
Yes, I see "degradation", unfortunately, even on modern cameras a low ISO is better. I am not sure. I think in the right direction, but also because of the large amount of detail in the landscapes that are lost.
Very much depends on the lens, how sharp the picture on the open aperture can be. In any case, it is better to cover the diaphragm with a stop. For example 20
mm f2.2
Thank you!
20 is fr in this case? (EXIF is not saved in properties).
Yes, I have just 28mm 2, it feels like 2,8, but it’s not clear with a large increase in the picture, because initially the picture is softer than modern lenses.
In the end, the avaricious pays twice. I have to go buy a tripod)
Just don't buy the lightest or most compact. Because it will be another “cheapskate pays twice”.
Thank you) I had to think about it, in any case I need something that will hold 2,5 +1 kg
If 2,5 is a lens, then the tripod foot is definitely. Not only will the load on the camera mount be uncomfortable to remove, it will constantly skew forward.
Just do not buy the heaviest and largest. This recommendation is as important as the previous one. Otherwise, he will lie at home. A simple tripod of a normal (not HAMA, ERA, etc.) company is quite suitable. It’s already more than 2 kg to carry a tripod
Somewhere I heard a recommendation that at first it’s easier to buy a simple one (no more than 3k). In a year he will be killed, and you will gain experience and understanding what you need)
I could be wrong. but lightness is often achieved through the use of aluminum, and it tends to bend
https://www.yarkiy.ru/goods/18818-cullmann-neomax-240-shtativ-s-sharovoy-golovoy