Do you know what the camera does with multiple exposures?

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Analysis:

Multiple exposure technology is to shoot several images on one page or one film image. You can shoot the same object several times, or several different objects together. Multiple printing involves repeatedly exposing a negative to the same piece of photographic paper multiple times. A similar technique called composite printing involves multiple exposures of several different negatives on one piece of photographic paper.

One way to take multiple exposures of an object with a camera is to leave the shutter wide open and simultaneously pulse a flash with a strobe, or flash several flashes in succession. Multiple exposures can also be obtained by turning an auxiliary shutter - an opaque disc with a small hole in it - in front of the lens. When making multiple exposures like this, in order to separate the images on the film slightly, the object, the camera, the zoom lens, or any two at the same time must be moved.

The second, more common method of multiple exposures is to open the shutter once for each exposure. For 35 mm and cameras that use winding film, this requires that the film does not roll when the shutter is wound. . Some cameras allow you to push the wind-up lever to wind the shutter and simultaneously move the ejection lever to prevent the film from rolling. If there are dark parts in each object, you can compose the image so that the main bright parts of each image do not overlap. For cameras that view from behind the focal plane, you can mark the position of each object on the viewfinder glass or covered white paper to obtain a precise composition. If the midtones and highlights of each image overlap, their exposures will be added together and recorded on the film. To avoid overexposure, each object only gets a portion of the total exposure. The exposure each object deserves is determined by the total number of exposures divided by the normal exposure. For cameras with automatic exposure control, you can multiply the total number of exposures by the film speed and use this speed to adjust the camera's light meter so that you can get the same correct exposure.

In multiple prints, the overexposure effect is also a problem. In the overlapping part, it will appear too dark. On film, the overexposed part will appear too bright when printed as a photo. On the slide Is it too bright? The problem of stable exposure during printing is relatively easy to solve through testing with paper strips and samples. A more important issue is to control the overlap and separation of images to an appropriate degree. This requires some method of gradual overlap so that the magnifying paper or lens can move appropriately between exposures.