Film is a direct exposure material in ordinary cameras. It can be roughly divided into negative film and reverse film (black and white or color). We usually use negatives. The image displayed by color negative is the complementary color of the real image color, that is, the opposite color. Black and white negatives are the same. The black thing on the film is transparent.
We print the film in the print shop, and then project it on photographic paper (the principle of photographic paper is similar to that of film), and the photo will restore the true color. Polaroid cameras don't use film, and there is no film, only photographic paper. But the difference between its photographic paper and ordinary photographic paper is that it has two layers. At one end of the photographic paper, there is a bag of potions. When the photo is taken out, it is squeezed by the camera roller and passes between two layers of photographic paper to show that the image medicine will not be squeezed out, because there is a strip-shaped medicine bag at the other end of the photographic paper to store the used medicine. The potions of polaroid photographic paper are very toxic, so try not to play with them.