What is the relationship between focal length aperture and depth of field for SLR lenses?

A little monk.

Just. Many people should understand the basics after playing a few times. Here is just a reminder, that is, to shoot people or scenes, this needs to be seriously considered, so that the problems of focal length, aperture and depth of field become more meaningful.

Novices generally like to open the aperture wide to get a nice bokeh, and large apertures can also get a large area of bokeh at focal lengths below 70mm, and the subject is sharp and prominent. But this does not seem to make much sense, the background area is so large but it is a virtual piece, what is the meaning of the background? It's better to use the medium telephoto directly, even if the aperture is smaller, you can still get the blurred background.

The relationship between focal length aperture and depth of field is easy to understand, but whether you want a background or not, and to what extent the background is blurred, that is something that needs to be thought about. A non-absolute view is: masters are actually better at using small focal lengths, small apertures to obtain a large depth of field to take pictures, if one day you no longer rely on large apertures and large depth of field to shoot very interesting**, then you are at least one in a hundred excellent photographers.

There are actually two issues here, namely the relationship between focal length and depth of field, and the relationship between aperture and depth of field. We know, depth of field.

It is the clear range that extends before and after the focus, this range can be controlled by different focal lengths and different apertures, what is the relationship between them? Let's take a brief look:

Photo by Xia Xue).

Focal length. Refers to the distance from the center of the lens (or lens group) to the focal point, in millimeters (mm), such as 50mm prime lens, 18-200mm zoom lens, etc., this value is the focal length.

The focal length is inversely proportional to the depth of field, i.e., the longer the focal length, the smaller the depth of field; The shorter the focal length, the greater the depth of field.

For example, the depth of field of a 24mm lens is greater than that of a 200mm lens, which means that the sharp range that extends before and after the focus is greater.

Photo by Xia Xue).

Aperture. It is an important part of the camera, which can control the amount of light entering the photosensitive surface inside the body, just as a faucet can control the flow rate. The aperture value is expressed by f, for example, the smaller the number, the larger the aperture, and the larger the number, the smaller the aperture.

The aperture is inversely proportional to the depth of field, i.e., the larger the aperture, the smaller the depth of field; The smaller the aperture, the greater the depth of field.

For example, the depth of field is smaller than that of f11, that is, the sharp range that extends before and after the focus is smaller.

Photo by Xia Xue).

Since the focal length and aperture of the SLR lens can determine the depth of field, large aperture and long focal length lenses are often used to shoot close-ups of people, flowers and plants in actual shooting, so as to blur the background to highlight the subject; Use a small-aperture, wide-angle lens to shoot landscapes, architecture, and other subjects to obtain clear images over a wide area. (Photo, text Xia Xue).

Depth of field is simply the sharp range of the subject being photographed. Control the depth of field to blur or make the scene as clear as possible. Once the focusing distance is determined, the lens aperture focal length is determined, and the depth of field is also determined.

This sharpness range is related to three factors, the title mentions two focal lengths and apertures, which are inherent parameters of the camera lens. The focusing distance, on the other hand, varies depending on the creator's performance.

In order to get a clearer idea of the depth of field, it is generally marked with old-fashioned manual focus lenses. For example, if the aperture of this lens is set to 2 and the focusing distance is in, then the clear range is roughly in between. The charm of a large aperture

If you set the aperture to 11, then the clear range will become meters. That is, the smaller the aperture (the higher the value), the greater the sharpness range and the longer the depth of field. This lens is a prime lens, and for lenses with different focal lengths, a telephoto lens is generally chosen to blur the background, so the longer the focal length, the smaller the depth of field.

This is also the secret of the wide-angle lens to shoot large scenery photos from far and near, and if you control the focusing distance well, you can achieve the effect of superfocal length, which is even more perfect

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The relationship between the focal length aperture and depth of field of a DSLR lens is inversely proportional to the relationship between the focal length and aperture of a lens in a DSLR lens and the depth of field.

First, the focal length of the lens is inversely proportional to the depth of field.

The longer the focal length of the lens, the smaller the depth of field, and the shorter the focal length of the lens, the greater the depth of field. So inversely proportional.

Second, the aperture of the lens is inversely proportional to the depth of field.

The larger the lens aperture, the smaller the depth of field, and the smaller the lens aperture, the greater the depth of field. So it's still inversely proportional.

So, if you want to shoot a very shallow depth of field, with a particularly noticeable bokeh, then you need a telephoto lens with a long focal length and a wide aperture to shoot.

If you want to shoot a particularly large depth of field, with almost full clarity in the frame, then you need a wide-angle lens with a short focal length, shooting with a small aperture.

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Depth of fieldsize, first withLens focal lengthRelevantly, lenses with long focal lengths have a small depth of field, and lenses with short focal lengths have a large depth of field.

Depth of field is calculated as follows: Depth of field (2 * diameter of the dispersion circle * square of the hidden focal length of the lens segment * aperture value.

The square of the focusing distance) (the 4th power of the focal length of the lens d the square of the diameter of the diffusion circle * the square of the aperture value * the square of the focusing distance) As can be seen from the formula, the rear depth of field > the foreground depth.

It can be seen from the formula for calculating the depth of field that the depth of field is related to the aperture used by the lens, the focal length of the lens, the shooting distance, and the requirements for image quality (expressed as the size of the allowable diffuse circle).

The three most important factors that affect depth of field are aperture, lens, and object distance.

1. The larger the aperture (the smaller the aperture value f), the shallower the depth of field, and the smaller the aperture (the larger the aperture value f), the deeper the depth of field.

2. The longer the focal length of the lens, the shallower the depth of field, and vice versa.

3. The closer the main body grips the hall, the shallower the depth of field, and the farther the main body, the deeper the depth of field.

The relationship between aperture size and depth of field.

Aperture plays a very important role in controlling depth of field. Remember a basic principle: the larger the aperture, the smaller the depth of field; The smaller the aperture, the greater the depth of field.

When shooting, if you want the front and back of the subject to be very clear, you can adjust the aperture as small as possible, such as f 16 and f 22Conversely, if you want the object in focus to be clear and blur some other scenes before and after, try to widen the aperture, such as f, or even f. (according to the aperture supported by the camera) while adjusting the aperture, it is also important to note that the amount of ** will also change, and you must rely on adjusting the shutter speed.

to balance; If the aperture is narrowed, the shutter speed will be slower; If the aperture is widened, the shutter speed will be relatively increased, and of course, if your camera has a A stop (aperture priority mode), we don't have to worry about the speed when you hit the A stop.

Lens focal lengthThe relationship between length and depth of field.

Generally speaking, at the same aperture, the longer the focal length of the lens, the smaller the depth of field, and vice versa. So the wide-angle lens.

There is a great depth of field, and the ultra-wide-angle lens will have sharp imaging a few centimeters away at its maximum aperture, but the telephoto lens.

Or telescopic lenses have a very small depth of field, sometimes only a few centimeters, and when you don't get it right, one eye will be clear and the other eye will be blurred.

The relationship between the distance and the depth of field.

However, when the aperture size does not change and the focal length of the lens used does not change, the farther away the subject is, the greater the sharp range between the front and back of the frame. Conversely, the closer the subject is, the smaller the sharp area in front and behind. This reminds us that when shooting some specific and close-up shots, we should focus very carefully, and be slightly negligent to make the subject go beyond the depth of field. The whole picture is gone.

On most 135 DSLR cameras, there is a simple depth of field table for viewing. Some depth-of-field tables sit between the lens aperture scale and the distance scale, and use a row of symmetrical aperture factors to indicate the depth of field range at a certain shooting distance for each aperture. Once you've adjusted the distance and selected the aperture, you can find the approximate depth of field range from the symmetrical two aperture scales, one for the closest point of the depth of field and the other for the farthest point of the depth of field.

The subject matter at a distance of two points will be relatively clear. Some single-lens reflex cameras also have a depth-of-field button** that allows you to see the clear range of depth of field before you take a photo, which is very convenient for photographers.

The larger the aperture of the aperture. The smaller the corresponding aperture value, the greater the amount of light entered. As for the focal length, it is related to your lens.

Generally, with a 100 mm lens, it is recommended to adjust the focal length. At least 100 mm can shoot clearly**. The shooting distance is related to the focus of your lens.

If your focal length is large enough, in fact, there is a relatively long distance, and you can shoot very clearly**. Depth of field is with you. Both the aperture size and the focal length are related.

Use a relatively small aperture with a wide-angle lens to shoot landscape long shots, while shoot with a relatively large aperture telephoto lens. Close-up macro lens with false focus.

With the same aperture factor and shooting distance, the shorter the focal length of the lens, the greater the depth of field range; The longer the focal length of the lens, the smaller the depth-of-field range.

For fixed focal lengths and shooting distances, the smaller the aperture used, the greater the depth of field.

Lenses with the same focal length are on different sensors, the larger the sensor size, the larger the angle of view, and the smaller the sensor size, the smaller the angle of view.

What is the lens

The lens has two fingers in film and television, one refers to the optical component used by the movie camera and projector to generate the image, and is composed of multiple lenses. A variety of different lenses, each with different modeling characteristics, their application in photographic modeling, constitutes an optical means of expression; The second refers to a continuous picture taken from the time the machine is turned on to the time it is turned off, or the clip between two splice points, which is also called a ytterbium head. One finger and two fingers are two completely different things'Concept, in order to distinguish the difference between the two, often refer to one as an optical lens, and two as lenses.

The lens referred to in film and television is not a lens in the physical or optical sense, but a lens that carries the image and can compose the picture.

The shot is the basic unit that makes up the entire film. Several shots make up a paragraph or scene, and several paragraphs or scenes make up a film. Therefore, the lens also guesses or constitutes the basic unit of visual language.

It is the basis of narrative and ideography. In the pre-shooting of film and television works, the lens refers to the sum of a piece of footage that the camera continuously captures from the time it is started to the time when it is stationary; In post-production, the shot is a set of rushing images between two editing points; In a finished film, a shot is the complete segment between the previous optical transition and the next optical transition.

The main function of the lens is to collect the reflected light of the illuminated object and focus it on the CCD, the image projected onto the CCD is inverted, and the camera circuit has the function of reversing it, and its imaging principle is the same as that of the human eye.

Lens classification

According to the origin of the lens, it is mainly classified as Japanese lenses and German lenses. The Japanese lens mainly has a better color reproduction, and the German lens has a strong sense of hierarchy. Chinese lenses in the market are also gradually occupying a certain market, mainly because they are relatively cheap.

01 Generally speaking, when taking pictures with a DSLR, the larger our aperture, the more blurred the background will be, and the smaller the aperture, the more realistic the background behind us, such as hail, and the more distinct the level.

02 When taking photos with a DSLR, we generally say that the larger the aperture, the smaller the depth of field. The smaller the aperture, the greater the depth of field. So the aperture and depth of field are inversely proportional.

03 When taking a DSLR, if the depth of field is shorter, then the focus that we can see is more on the subject, that is, in the foreground.

04 When taking a DSLR, if the depth of field is getting longer and longer, then we can see that the object in the photo is more layered, and its aperture is smaller.

The relationship between the focal length of the lens and the depth of field and hail

The focal length of a lens is a fixed physical size, which is how much it is, and does not change depending on the format of the camera. Lenses with the same focal length are placed on cameras of different formats, and the larger the frame, the larger the angle of view; The smaller the frame, the smaller the angle of view. For the same frame body, if the lens focal length is longer, the depth of field will be shallower; The shorter the focal length, the greater the depth of field.

Lens focal length: refers to the distance from the principal point to the focal point after the lens optics, which is an important performance indicator of the lens. The length of the focal length of the lens determines the size of the image, the size of the field of view, the depth of field, and the perspective strength of the image.

Depth of field: The range of the distance between the front and back of the subject as measured by imaging that can obtain a clear image at the front of the camera lens or other imager. The aperture, lens, and distance of the subject are important factors that affect depth of field.

In photography, lens focal length and depth of field are two very important concepts. Lens focal length refers to the focusing distance of a photographic lens, while depth of field refers to the depth range of clear images in photography.

In general, the longer the focal length, the shallower the depth of field; Otherwise, the depth of field will be deeper. This is because a lens with a longer focal length is able to focus on objects farther away at the same shooting distance, but at the same time, it can also blur objects near and far.

Therefore, photographers need to choose the appropriate focal length of the lens according to the subject and style of shooting. For example, if you're shooting portraits, you'll need to choose a lens with a longer focal length to blur the background and accentuate the subject. On the other hand, if you want to shoot landscapes or Suiyuanfeng buildings, you need to choose a lens with a short focal length to ensure that the whole scene can be clearly presented.

In addition, the depth of field can also be controlled by the aperture size and the camera's focal length setting. The wider the aperture of the camera, the shallower the depth of field. Conversely, the smaller the aperture, the deeper the depth of field. The adjustment of the focus distance also affects the depth of the depth of field.

In general, lens focal length and depth of field are very important photographic concepts, and their interrelationship directly determines the quality of the shooting. Therefore, photography enthusiasts need to have an in-depth understanding and mastery of it in the usual shooting process in order to achieve better shooting results.