How to master the aperture when taking pictures

The smaller the value after f, the larger the aperture. The function of the aperture is to determine the amount of light entering the lens. The larger the aperture value, the more light enters. On the contrary, the smaller. Simply put, under the condition of constant shutter, the larger the aperture, the more light enters and the brighter the picture; The smaller the aperture, the darker the picture.

Aperture and shutter are two tools to control the amount of light in photography. Aperture refers to the size of the opening in the middle of the lens, which controls the brightness of light when film or CCD is exposed. In fact, the aperture adjusts the amount of light according to the pupil structure of the human eye. The end of the aperture consists of a circle of thin and overlapping metal blades, and the openings of the blades form a circle. Zooming in or down can control the amount of light entering.

Aperture unit

The size of the aperture is determined by its aperture value (f number). Generally all lenses have this aperture series. In the specification table of the camera, the manufacturer usually provides two aperture values (see the red box in the attached figure). These two data, one by one, represent the maximum aperture value of the camera lens. One set of data refers to the aperture at the "wide-angle end", such as F2.6, and the other set is at the telephoto end. For example, the digital camera in the left specification table is a 3x optical zoom, so at the 3x optical zoom end, the maximum aperture is not F2.6, but F4.7 This figure also shows the range of the maximum aperture change of this camera when zooming.

Whether it is a digital camera or a fool camera, today's aperture representation still follows the traditional practice. The standard aperture series are: f/ 1, f/ 1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/1,f//kloc. F/ 1 is the maximum aperture value. In the above series, the adjacent aperture series and the subsequent series are half of the light quantity of the previous series. For example, the aperture of the lens is set to f/4, and the amount of light it lets in is half of that set to f/2.8; Or just the aperture is set to a quarter of the f/2 light amount.

Aperture formula

The numerical representation of the aperture is mysterious, but the larger the number, the smaller the aperture. In fact, the size of the aperture can be expressed by a formula, which is expressed in bold and bold as follows:

Aperture value (f $ NUMBER) = lens focal length (mm)/aperture (mm).

Let's take a 50mm standard lens as an example. If its maximum aperture (that is, the aperture of the aperture blade, not the aperture of the lens) is 36mm, then the maximum aperture value of the lens is equal to f/ 1.4(50/36 = 1.4). Because the aperture size is limited, the maximum aperture value also has its limit. At present, the maximum aperture of the standard lens of 135 traditional cameras is f/ 1.0, and the digital cameras are f/ 1.8 of Olympus C-5050Z series, followed by f/2.0 of professional digital cameras. Generally, the aperture below f/5.6 is called large aperture; Above the aperture f8, it is called a small aperture. The smaller the aperture, the wider the depth of field and the clearer the picture; The larger the aperture, the shallower the depth of field and the more blurred the picture. We will discuss the depth of field separately below.

The value of aperture

The change of aperture size can not only change the transmittance, but also control the depth of field. Especially in portrait shooting, the requirement of depth of field is emphasized. Because the maximum diameter of the aperture is mainly affected by the lens size of the lens, if you want to enlarge the aperture, you must enlarger lens under the standard specifications, and enlarger lens will lead to more expensive costs and manufacturing expenses. In the world of traditional cameras, if the aperture is larger than the previous level, the price will often rise in proportion. Therefore, no secular lens can have all the apertures when it is manufactured. For general-purpose 35mm camera lenses, the aperture is mostly from f/ 1.4 to f/22. Only the aperture of the special lens of the large camera (4X5) is as small as f/64, but the maximum aperture is also limited to f/5.6.

Aperture and depth of field

Opening the aperture of the camera can speed up the shutter speed, which is very useful in dim indoor light. The large aperture allows you to take stable photos without a tripod. Secondly, the smaller the aperture, the deeper the clear range of the scene, which is also one of the definitions of depth of field.

When shooting with a large aperture, the photo results show a relatively shallow depth of field, with a clear foreground and a blurred out-of-focus scene behind it. If you shoot with a small aperture, the photos you take will have a different feeling. As a result of small aperture shooting, the lens is focused in the middle and you can see a deep depth of field. The foreground and background are enough for everyone to see clearly.

Matching of Aperture and Shutter (Aperture Precedence Mode)

Shutter speed and aperture will affect the amount of light entering the camera. To take a correctly exposed photo (which looks neither too bright nor too dark), the negative or CCD must get the correct amount of light. The combination of aperture and shutter can help you control the light successfully. The relative aperture and shutter can also be balanced, and they are inversely proportional. As long as the setting of one side is changed, the other side needs to be adjusted reversely. So if you use a faster shutter distance, you need to set a larger aperture, or use a slower shutter speed and a smaller aperture value. Although the interaction between the two can achieve the balance of light entering, the shutter speed determines the definition of the moving subject, which is equivalent to the horizontal definition; Aperture determines the depth of field, which is equivalent to the vertical clear distance.

Many photographers prefer aperture depth of field to adjust the tone of photos. This aperture size defines the subject, which is commonly known as the "A" aperture prerequisite mode. Simply put, it is to set the aperture, such as f/5.6, take a picture after half pressing the shutter, and get the exposure shutter value from the fuselage. In this case, it is much better than manual adjustment, which will miss the aperture and shutter speed, resulting in overexposure (the photo is all white without layering) or underexposure, resulting in the photo being all black and losing the dark details. Although, the smaller the aperture, the more concentrated the light, and the easier it is to clearly image the depth of field. However, if the aperture is too small, diffraction will occur, but it will be blurred (for example, a self-made pinhole camera can't see anything clearly if the aperture is too small).

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