Teach you how to adjust the aperture value

In daily shooting,aperturePriority (Av) is undoubtedly the most commonly used shooting mode. In this mode, we must manually set aaperture

And then adjust other shooting parameters to control the exposure. So the question is, how to choose the aperture value? What are the different picture effects of large aperture, small aperture and moderate aperture? What are the precautions for using these aperture values?

The same aperture value brings different effects, which is suitable for different themes. Don’t worry, this will be explained for you slowly~

1. Advantages and applications of large aperture

With a large aperture below f/4, the depth of field is very shallow, and the clear range outside the focal plane is very small. It is easy to capture the effect that the subject is blurred and the background is clear, effectively separating the subject from the background. As shown in the following figure, under the large aperture, other flowers close to the main body become blurred, effectively highlighting the main body.

The common application of this feature of large aperture in daily life is beauty portrait and still life. When shooting a portrait, the most troublesome thing is to choose the background. The background is too messy, and there are too many eye-catching still life, which is a headache. As long as you open the aperture, these problems will be solved. Everything will turn into a colorful color, and only the face of the subject is clear

It looks beautiful, but it seems to lack some aftertaste connotation. This kind of photos with a paste background, a beautiful subject, and a beautiful but not very meaningful look are called sugary water photos. It’s a good thing that you can take pictures with sugar water, but it’s not a good thing that you can only take or be satisfied with taking pictures with sugar water – this is a great enemy for you to improve your photography!

In addition to portraits, still life photography, including commodity display, plant and flower photography and even food photography, can use large aperture to highlight the main effect.

In street photography, tourism photography and other subjects, because the background is often messy, it is also very common, or even the only way, to “dictate” your subject with a large aperture. The shallow depth of field created by using the large aperture only makes the subject clear while blurring other scenes. The audience can easily see which subject is and what theme you want to express.

As shown in the following picture, the big aperture clearly tells the audience: “I took the pair of people who are playing in the lower right corner, not the group of tourists and the huge Ferris wheel.”.

In a word, the biggest role of large aperture is to highlight the main body, make the background vague and create a sense of hierarchy. The watchman said, “Is the big aperture hot? Is there any harm?” The sky has the sun and the moon, and the earth has yin and yang. Everything has both good and bad sides, and the big aperture is no exception. Next, we will talk about some common problems in the practical application of large aperture.

2. The problem of large aperture

The shallow depth of field produced by large aperture will bring a serious problem, that is, sometimes the depth of field is too shallow. What is “too shallow a depth of field”? A picture shows everything! As shown in the figure below, the depth of field is too shallow, so shallow that half of the face is blurred – if the photo is taken by the girl’s boyfriend, it is estimated that he will be punished!

This example is a bit extreme. Few people are so careless that half of their faces are blurred without being aware of it. But even if the whole subject is in a clear range, another problem still exists.

That is, if the aperture is too large, the sharpness of the subject will be reduced, that is, the clarity and detail expression will be insufficient. It may be a little hard to understand just using words to explain. Let’s give an example. The stone lion on the left side of the picture below is obviously the main body of the picture, which is located in the clear range of the picture as a whole. It seems that there is no big problem:

But! Yes! Although it seems that the whole of the subject is clear, in fact, there are differences in the clarity of each part. In the red circle below, the face of the stone lion is the focus, which is the clearest; In the blue circle below, the lion’s curly hair, which is a certain distance from the face plane, looks clear, but if you zoom in and look carefully, you will find that many details are missing.

This is a significant problem in large aperture shooting: the subject is not sharp enough, and it may be impossible to give consideration to the details of each part of the subject.

Of course, some people think that this is not a problem, but a benefit worth taking advantage of. For example, this talented man uses a large aperture to lighten the pimple on his girlfriend’s face. As shown in the following figure, the larger the aperture, the less obvious the defects on the face – of course, he seems not to care about the problem of “one eye is clear and one eye is blurry”

In addition, the picture quality of the lens at the maximum aperture may also be slightly reduced. The more the entry lens is, the more serious this phenomenon is. Therefore, it is better to reduce the aperture by one to two degrees before using it.

Another problem is that aperture is a factor in controlling exposure as well as depth of field. If you shoot with a wide aperture on a sunny day in the sun, without a dimmer lens, and the camera’s maximum shutter speed is not very high, your photos may be overexposed:

Well, after talking about so many big apertures, it’s time to talk about small apertures, otherwise it’s too unfair for small apertures

3. Advantages and applications of small aperture

Contrary to the large aperture, the small aperture has a large clear range, which can best play the “record” function of photography, and is applicable to scenery, tourism, documentary and other shooting topics. The scenery is basically shot with a small aperture. With the pan focus operation, the entire large spatial scale image can be located in the clear range.

The nearby trees and the distant mountains are clear

OK. Next, let’s talk about the practical application of small aperture. what? You asked me, “Why don’t you continue to talk about the application of small aperture, which is too few?”? Please, the small aperture can keep the overall picture as clear as possible, and restore the picture you see to the maximum. This has played a huge role. Need I say more?

4. The problem of small aperture

As I said before, a small aperture can obtain a large depth of field, making the picture clearer. So, the smaller the aperture, the better? Not really. Everyone who has studied physics knows the experiment of “small aperture diffraction”, but the aperture just becomes a small aperture under a very small aperture value, which may cause diffraction and affect the picture quality partially.

For a picture taken under the small aperture of F22, we enlarge the red box to get the small picture on the lower left; Compared with the normal shooting area, it is found that the picture quality has lost.

Schematic Diagram of Image Quality Loss Effect Comparison of Small Aperture Diffraction

It can be seen that small aperture diffraction will cause a certain degree of image quality loss. Although it has little impact on the overall, it is better to avoid it as far as possible. Therefore, in general, it is better not to drive to the minimum aperture, but to the penultimate or third gear.

Another problem with small aperture is that hand-held shooting in low light environment may cause the shutter speed to decrease and shake when it is lower than the safety shutter value:

I can’t see the shaking night scene

The solution is also very simple. Adjust the ISO to avoid making bad films at the cost of noise; Or take a tripod and use a low speed shutter at the expense of extra physical strength.

Now, we have explained the basic characteristics and problems of large and small apertures. Next, we will explain the different optical effects that large apertures and small apertures can produce.

5. Optical effect of aperture

The optical effects produced by the aperture size are mainly reflected in the manifestation of point light source in the picture. For example, under the same time, place and other shooting parameters, shoot two suns with different aperture values. The effect is as follows:

It is obvious that the sun on the left is much larger than that on the right. When shooting the starry sky, some people also use this feature to open the aperture to make the stars bigger, brighter and more obvious.

Let’s take another example. Under the same parameters, use different aperture values to shoot the sunlight exposed in the tree gap.

It can be seen that under the large aperture, the point light source is relatively concentrated, showing an expanding sphere; However, under a small aperture, the light source shows a divergent trend, forming radiation that diffuses around. According to this basic principle, large aperture is often used to create out of focus speckle — the small round spots in the background below, isn’t it beautiful~

The small aperture is used to shoot the stars of the sun and street lamps.

A small aperture is also required to take pictures of Jesus’ light in nature in a large range, or just take the sunlight into columns and rays in a small range.

6. Best aperture

Many people have held the view that the picture with a small aperture is clearer than that with a large aperture. In fact, this view is not accurate, because a small aperture is just a larger range of clarity, not a higher degree of clarity. To discuss the question of “which aperture value is the clearest picture”, we need to compare the clearest part of each aperture value picture, namely focal plane imaging horizontally.

How about horizontal comparison? Let’s look at an example. First, select a scene, preferably one with bright color contrast or light and dark contrast, so that we can zoom in and observe the details.

Use a tripod to fix and focus on the same area – it is better to choose the edge of the scene with a sense of hierarchy. Specifically, in this picture, the pine needle in the center of the picture is selected as the focus area, and the edge between the pine needle and the scene, and the shadow edge of the pine needle projection on the ground are mainly observed.

Keep other shooting parameters except the aperture value unchanged, and take several photos with different aperture values. Select two images of f/22 and f/9 for comparison. Observe the pine needles and the shadows cast. It is found that the shadow edge in the left figure is more blurred than that in the right figure.

This shows that f/9 is more sharp than f/22 for this lens. It is better to copy the picture to the computer and magnify it for observation, so that the comparison results can be obtained more intuitively and accurately. Repeat several similar comparisons, and we can get several aperture values with the highest sharpness. Under these aperture values, the lens has the sharpest and clearest image, or the highest sharpness.

Generally speaking, the best aperture is usually a medium aperture value. Of course, the best aperture value is only a reference. In actual shooting, we should first consider the depth of field, and then consider using the “best aperture” when there are no special requirements for the depth of field.

7. Focus and maximum aperture

The maximum aperture that a lens can use is often affected by its focal length. Generally, the longer the focal length is, the smaller the maximum aperture that can be used. For example, the zoom head of a brand is marked “1:4-5.6,18-50mm”, which means that when you use the 18mm wide angle end, the maximum aperture value available is f/4; As you increase the focal length, the maximum aperture value becomes smaller. When you use a 50mm focal length, the maximum aperture value becomes f/5.6.

Of course, you can also purchase a “constant aperture” zoom head to ensure that the maximum aperture value under any focal length remains unchanged. However, this kind of lens is much more expensive. Please think twice before buying it. The telephoto mirror will also lead to the decrease of the maximum aperture value available. The telephoto mirror of x1.4 will decrease by one gear, and the telephoto mirror of x2 will decrease by two gears. By analogy, children who like to pursue large aperture should be careful to use it!