What are the basic terms and meanings of photography?

Brief introduction of common photographic terms

Focal length-the distance from the center of the lens to the focal point. The unit of focal length is usually expressed in mm, and the focal length of the lens is usually marked in front of the lens, such as f=50mm (this is what we usually call "standard lens"), 28-70mm (our most commonly used lens), 70-2 10mm (telephoto lens) and so on.

Aperture-A device used to control the amount of light passing through a lens.

Shutter-A device used to control the exposure time. Shutters can generally be divided into curtain shutters, lens shutters and steel shutters. Among them, curtain blinds can be divided into vertical curtain blinds and horizontal curtain blinds. Steel shutter can reach higher speed (the highest shutter speed can reach112000 seconds or more at present). Generally, the highest speed of the inter-mirror blade shutter does not exceed 1/500 seconds, but the biggest advantage of the inter-mirror blade shutter is that the noise generated during shooting is extremely low, which is very conducive to sneak shots and can realize synchronous flashing within the full speed range.

Shutter speed-the time when the shutter is open. It refers to the time (exposure time) when light sweeps across the film. For example, "1/30" means that the exposure time is 1/30 seconds. Similarly, "1/60" means that the exposure time is1/60s, and the shutter of1/60s is1/30s. The rest and so on.

Note: Some materials refer to shutter speed as shutter time. The two names are different, but they mean the same thing, both referring to the shutter opening time.

Depth of field-the relatively clear range of an image. The depth of field depends on three factors: the focal length of the lens, the distance between the camera and the subject, and the aperture used. The relationship between depth of field and the above three factors is: the longer the focal length, the shorter the depth of field; The shorter the focal length, the longer the depth of field (for example, under the same aperture and distance, the scene of 28mm lens is far greater than that of 70mm lens); (2) The closer the distance is, the shorter the depth of field is, and the farther the distance is, the longer the depth of field is (for example, under the same focal length and aperture, the subject scene at 10 m is far greater than the subject depth of field at 1 m); (3) The larger the aperture, the shorter the depth of field, and the smaller the aperture, the longer the depth of field (for example, under the same focal length and distance, the scene with the aperture of F 16 is far greater than the depth of field with the aperture of F4).

Sensitivity-indicates the speed of the photosensitive material. The unit of sensitivity is "degree" or "fixed". For example, "ISO 100/2 1" means a film with a fixed sensitivity of 100/2 1. The higher the sensitivity, the more sensitive the film is (that is, the less light is needed to shoot the same photo normally in the same shooting environment, that is, a higher shutter or a smaller aperture can be used). The sensitivity of 200-degree film is twice that of 100-degree film, and that of 400-degree film is twice that of 200-degree film, and so on.

Color temperature-Different pigments contained in different kinds of light are called "color temperature". The unit of color temperature is "K" (Kelvin). The color temperature we usually use is 5400 K-5600 K; The color temperatures that light types A and B can adapt to are 3400K and 3200K respectively. Therefore, different types of films should be selected according to the subject and environment, otherwise there will be color cast (unless the color temperature is corrected by color filter).

Attachment: Definition of color temperature "Suppose there is a black metal in an environment of minus 273 degrees (absolute zero). With the increase of temperature, black metal will emit light with different wavelengths, and the metal color temperature corresponding to colored light plus 273 is the color temperature of light. " For example, when a metal is heated to 2500 degrees Celsius, it will emit red light, and the color temperature of this red light is "2500+273" K, which means that the color temperature of this red light is 2773 K. The lower the color temperature, the higher the percentage of long-wavelength light (red and orange light). The higher the color temperature, the higher the percentage of short wavelength light (blue light and purple light). For example, the color temperature of sunlight at noon is about 5500 K; The color temperature of the flash is about 5600 k; The color temperature of the blue sky is about 20000 k; 100 watt light bulb's light color temperature is about 2600K K.

Exposure-the process by which light reaches the surface of the film and makes the film sensitive. It should be noted that by exposure, we mean film exposure, which is a necessary process for us to obtain photos. This is very different from what non-professionals call "exposure". What they call "exposure" refers to the accident that the camera leaks light and causes the film to fail.

Relative aperture-the ratio of the effective aperture (beam diameter) of the lens to the focal length. The larger the relative aperture, the faster the lens speed. Such as 1:2.8, 1:3.5-4.5, etc. Among zoom lenses, lenses with fixed relative aperture are generally called professional lenses, lenses with fixed relative aperture but between 1:2.8- 1:4 are called quasi-professional lenses, and the rest are called mass lenses.

Exposure combination refers to the combination of different apertures and shutters that can be used in the same shooting environment. For example, the shutter measured by the exposure meter is 1/30 seconds, and the aperture should be 5.6, so F5.6 and 1/30 seconds are an exposure combination. We can also use the exposure combination of F4 and 1/60 seconds instead, and we can also use the exposure combination of F2.8 and1125 seconds instead. In other words, these combinations are equivalent. However, it should be noted that although these exposure combinations are equivalent, that is to say, the exposure is accurate, but the depth of field obtained by different combinations is different.