Know the answer to practical photography technology

The effective aperture of a lens refers to the ratio of the beam diameter to the focal length passing through the front lens of the lens. Usually, except for the wide-angle lens, the diameter of the front lens is about equal to the beam diameter, so the effective aperture of the lens is the largest first-order aperture of the lens, that is, the largest aperture of the lens.

Relative aperture: one of the important parameters of optical lens, expressed by the ratio of effective aperture to focal length of lens. The relative aperture is a ratio. The relative aperture indicates how much light the lens receives.

There are three kinds of lenses: wide angle, medium focus and telephoto.

Wide-angle lens is characterized by pushing the scene into the distance, which is large near and small far, with the advantages of large depth of field and wide shooting range. The disadvantage is that the deformation is large, and there is generally some barrel distortion.

The feature of medium focus is that it is easy to make a large aperture, which is suitable for shooting portraits and landscapes.

A telephoto lens is characterized by a strong sense of compression, which can draw distant objects very close, and the effect is more obvious with the extension of the focal length!

The aperture coefficient of 1-32 is f/32f/22f/16f/11f/8f/5.6.

The F/4 aperture and F/ 16 aperture differ by three apertures, and the luminous flux of the former is 16 times that of the latter.

Usually add [f/] before the relative aperture to indicate the relative aperture, such as f/ 1.4, f/2, f/2.8, etc. F/2 is also expressed by 1:2. Usually, there are many lens labeling methods like 1:2.

Aperture marks are arranged in a series of √2 times.

The viewfinder is the window to observe the scene with your eyes when shooting. Its function is to judge whether to adjust the shooting elements (image size, distance, height, viewing angle, depth of field, realism, color, light and shade, horizontal or intentional tilt, master-slave relationship, collocation, foil relationship, position in the image, composition, etc. ) By observing the scene in the viewfinder.

The function of the aperture is to accurately adjust and control the luminous flux of the lens and correctly expose the photosensitive materials; Under the condition of reducing the aperture, some residual aberrations of the lens can be reduced; The depth of field can be controlled by the contraction or enlargement of the aperture, with small aperture and long depth of field, and large aperture and short depth of field.

Factors affecting the depth of field: assuming other conditions are the same;

(1), lens aperture:

The larger the aperture, the smaller the depth of field; The smaller the aperture, the greater the depth of field;

(2), the lens focal length

The longer the focal length of the lens, the smaller the depth of field; The shorter the focal length, the greater the depth of field;

(3), shooting distance

The farther the distance, the greater the depth of field; The closer the distance, the smaller the depth of field.