The principle of old-fashioned cameras

The old camera actually uses the imaging principle of convex lens. A convex lens, let the focal length be f (the convex lens can converge light, the point where the light converges is called the focal point, and the distance from the focal point to the center of the convex lens is the focal length), and the object distance (the distance from the object to the center of the convex lens) be u, then when u >; 2f. Put an opaque object on the other side of the convex lens, which is called a light screen in physics. On the light screen, you can get an image exactly like the real thing, but this image is inverted and reduced.

That's how cameras work. There will be a convex lens in front of a traditional camera, which is what we call a lens. This convex lens plays the above role. Behind the convex lens is a darkroom, in which there is a negative film coated with photosensitive substances. The negative is in a dark room, so it is not sensitive because it is sealed and dull. Press the shutter, the shutter opens, and the light enters the darkroom through the convex lens, forming an inverted reduced image on the negative. Shutter opening and closing speed is very fast, the fastest is only one thousandth of a second. Professional cameras can also control the opening and closing time of the shutter, so that the film can be exposed for a long time to achieve the desired effect.

Because the focal length of the convex lens used in the camera is relatively small, the subject can always be out of twice the focal length, and an inverted reduced image can always be formed on the negative.

There is a difference between a fool camera and a professional camera. The fool machine has only one convex lens, so it can't adjust the exposure time and doesn't need any settings. This is a camera that a fool can use. But in this case, you can't shoot professionally.