Is the exposure of film negatives exposure?

1, no, sensitivity is the sensitivity of film to light. Exposure refers to the process that the light emitted or reflected by the photographed object is projected onto the photosensitive film through the camera lens, causing chemical or physical changes and development. It also means that something is exposed or exposed.

2. Sensitivity is the sensitivity of film to light, and it is also the photosensitive ability and symbol of film. Film can be sensitized in weak light, which is called high-speed photosensitive (fast) film; On the contrary, films with low sensitivity should be shot under strong light. When films with different sensitivities are shot under the same light, the aperture or shutter speed of the camera should be changed, that is, films with high sensitivity should have smaller aperture and faster shutter speed. Low-sensitivity film, on the other hand, has a larger aperture or a slower shutter speed. Film sensitivity is expressed in ASA or ISO (ASA and ISO refer to different standards). It shows the sensitivity of film to light, which ranges from ISO25 to ISO6400. The higher the film sensitivity, the more sensitive it is to light, so it can be shot under weak light source; But the higher the sensitivity, the coarser the particles, and the coarser the enlarged photos will appear. High-sensitivity film (above ISO400) is often used for window, indoor, night scene or stage photography. The lower the sensitivity, the finer the film particles and the better the texture, but the more light is needed, so it is necessary to have good light or use a tripod when shooting. Low-sensitivity film (below ISO 100) is suitable for portrait or landscape photography.

3. Exposure is the combination of aperture and shutter.

It can be considered that the aperture (numerical value) is actually how big the small round window is, and the shutter (speed) is how long the window has been open. Assuming that the window is only open for 1/4 4 seconds, it is obvious that if the window is half open for 2 seconds, the film can be exposed correctly, because1/4 * 4 =1/2 * 2 =1,and the light input is the same. Similarly, if the window is fully open, the exposure time only needs 1 second. If the aperture of a lens is F4, and in photographic terms, the shutter speed of F4 is 1 sec, which is the correct exposure value, then F5.6 and 2 seconds, F8 and 4 seconds can also get accurate exposure pictures. Important conclusion: A correctly exposed photo can have n different combinations of aperture and shutter speed.

4. To sum up the explanation of the above terms, there are three factors that can affect whether a picture is exposed correctly: aperture, shutter speed and ISO (sensitivity). Among them, aperture and speed jointly determine the amount of light entering, and ISO determines the photosensitive speed of ISOCCD/CMOS. If the light input is not enough, we can open the aperture or slow down the shutter speed, and if not, we can increase the sensitivity (ISO). The disadvantage of large aperture is that the resolution is not as good as that of middle aperture. If the shutter speed is reduced, the picture may be pasted, and the quality of the picture will also decrease after the ISO is improved. Without a perfect plan, how to choose should be flexible.