What does exposure in photography mean

The process of exposing the photosensitive film through the objective lens when taking pictures. The exposure (h) is the product of the illuminance (E') received on the photosensitive film and the exposure time (t), and the unit is Le? The second formula is as follows: the illuminance (e') received on the photosensitive film is controlled by the relative aperture of the photographic objective. The exposure time of camera is controlled by shutter; The exposure time (t) of a movie camera is controlled by the camera frequency (n, the number of shots per second) and the shutter opening (α). The formula is as follows: for a certain film, under certain development and development conditions, the required appropriate exposure is certain.

Photographic exposure is carried out at the moment of shooting, but its realization is inseparable from the influence of development stage and negative development on density, tone and hue. Therefore, it is a key measure to control the factors that affect the degree of development (such as selecting the appropriate development process, developer formula, development time and temperature).

The accurate control of photographic exposure must be based on exposure measurement, and the shooting measurement must be carried out under exactly the same conditions as the actual shooting. The basis of choosing exposure combination is an important content of photographic exposure. In photography practice, exposure can be determined according to the illuminance accepted by the scene or the brightness of the scene. The determination of photographic exposure should also pay attention to the width of the film and the brightness range of the scene.

Whether photographic exposure is appropriate or not is closely related to the brightness balance in the shot picture. For a large area of the picture that is too bright and too dark, we can adjust it by adjusting the lights, deploying the scenery or using the foreground and props. After fully understanding and mastering the performance of photographic equipment, the principle and use method of exposure meter, photographic exposure should be combined with the conditions of photography and development, especially the development method, exposure measurement and production test, light measurement and ordering, reference brightness selection, tolerance application and artistic treatment of brightness balance.