Getting started with the camera

The aperture is the part of the camera that controls the size of the lens aperture to control the depth of field, the quality of the lens image, and the amount of light that is coordinated with the shutter. The expression aperture size is represented by the f value. For a lens that has already been manufactured, the diameter of the lens cannot be changed arbitrarily, but the lens light can be controlled by adding a polygonal or circular shape and a variable aperture grating inside the lens. The device is called the aperture, and the aperture f value = the focal length of the lens / the diameter of the lens aperture. The illuminance of the light reaching the photoreceptor or chip through the lens is proportional to the square of the aperture aperture and inversely proportional to the square of the aperture number.

The sequence of apertures of commonly used lenses is 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45, 64, 90, 128.

The smaller the aperture number, the larger the aperture. The larger the aperture, the more the amount of light is transmitted during the same exposure time; the smaller the aperture, the less the amount of light passing through the same exposure time. Therefore, at the same shutter time, the larger the aperture, the more the amount of light passing, the brighter the picture; the smaller the aperture, the darker the picture. Under the same exposure conditions, the larger the aperture, the shorter the exposure time required, and the smaller the aperture, the longer the exposure time required. Therefore, in normal shooting situations, the aperture is directly related to the shutter speed.

The aperture also determines the depth of field of the photo. Under the same focal length and shooting distance, the larger the aperture, the smaller the depth of field, and the smaller the aperture, the larger the depth of field.

A typical lens can adjust the aperture within a certain range. The lens is usually only marked with the maximum aperture, but the minimum aperture is not marked. For example, a lens labeled 35mm F1.4 has a maximum aperture of 1.4, but the aperture can be adjusted to F2.0 F5.6 and so on, and another 35mm F2.0 lens, the maximum aperture is 2.0, can not be adjusted to F1.4 anyway, but can be adjusted to a smaller F5.6 F8.0, etc. Wait. For example, a lens EF 28-300mm F3.5-5.6L IS, this zoom lens can be seen from the name of the wide-angle end (28mm) maximum aperture is 3.5, telephoto end (300mm) maximum aperture is 5.6, by the way The minimum apertures at the wide-angle end and the telephoto end are 22 and 40, respectively.

In general, the lens of the same focal length, usually the quality of the large aperture is higher, and the price is higher.

A fixed focus refers to a lens with a fixed focal length, and a zoom head refers to a lens with a fixed focal length.

Since the zoom lens can be adjusted because of the focal length, it is convenient to use. In addition, the design usually pays more attention to portability and cost performance, so most of them are simple in structure, easy to carry, and relatively inexpensive.

The fixed-focus lens is generally designed and manufactured to meet the needs of high image quality. Although it is a fixed focal length, it is not convenient to use the zoom lens, but the price is generally higher than the general zoom lens, and it is heavier than the general zoom lens, but the fixed focus lens It has a large aperture and its imaging quality is much higher than that of a general zoom lens. In addition, fixed-focus lenses are usually designed for the most common focal lengths, so although they are not zoomable, they are still very useful.

Commonly used zoom lenses (the following lenses are produced by many manufacturers)
17-85mm 18-55mm 18-135mm 18-200mm 28-135mm 28-200mm 60-300mm 75-300mm These are usually cheap zoom lenses
16-35mm 17-40mm 17-55mm 24-70mm 70-200mm These are usually high-priced zoom lenses

Generally, there are common fixed-focus lenses (the following lenses are produced by many manufacturers)
24mm F1.8
35mm F1.4
50mm F1.0/F1.4/F1.8
85mm F1.2/F1.4/F1.8
100mm F2.8 (usually a macro lens)
135mm F2.0
200mm F2.0/F2.8
300mm F2.8/F4.0
400mm F2.8/F4.0/F5.6
600mm F4.0, etc.
>>>>>>>>>>>>Camera lens

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