Understand the imaging principle

What kind of instrument is a camera? Why can you condense the external scenery into a small photo? Observing the camera in your hand, you will feel that so many buttons, numbers and switches must be very complicated. In fact, even the most advanced cameras are composed of lens and body, and the imaging principle is the same.

1, "pinhole imaging"

Blocking a plate with a small hole between the screen and the object will form a reflection of the object on the screen. We call this phenomenon pinhole imaging. Move the midplane back and forth, and the image size will change accordingly. This phenomenon reflects the essence of light propagation along a straight line.

2. Before the invention of the camera, people began to use the principle of "pinhole imaging" to manufacture various optical imaging devices, which were called "Cameraobscura". /kloc-In the first half of 0/9th century, people finally found the method and medium to store the optical image on the projection plane in the black box, and the camera industry started from this, so the black box is considered as the ancestor of the camera. And "Camera" became the English name of the camera.

camera bellows

Schematic diagram of black box use

3. The invention of the camera

1839, French painter Daguerre invented the world's first camera according to the pinhole imaging principle, which was called "the diorama". However, the camera at that time was unimaginable to modern people. The camera box is as big as a small house, and the shooting time is at least 30 minutes, so that the subject's head has to be fixed in a pre-made clip, and all he gets is a heavy bronze plate. At that time, a newspaper reporter commented: "It's like holding a mirror on the road, reflecting the surrounding scenery in great detail, and then taking the mirror home."

184 1 year, British scientist and chemist Talbot invented the negative film technology. Instead of "printing the image on a thick copper plate and taking it home", the image is printed on low-cost paper through the negative, which greatly reduces the cost and leads to the emergence of commercial cameras for ordinary people to take pictures. Although it was still rough and crude at that time, it already had the basic performance of modern cameras. Since then, photography technology has been widely spread all over the world, and photographic equipment has been continuously improved.

After 170 years of historical evolution, the camera has gradually developed from a huge "peep show" to a small and exquisite precision instrument with simple operation and excellent performance, and has begun to develop towards full automation, multi-function and high definition.

From 65438 to 0839, French painter Daguerre invented the world's first camera based on pinhole imaging principle, which was called "peep show".

Basic components of a camera

A camera is like a mysterious box. Just like our eyes, we can clearly see the external scenery, and at the same time, we can print what we see on the negative. If you carefully observe the camera in your hand, you will find that both advanced cameras and popular cameras are composed of five parts: body, lens, aperture, shutter and viewfinder. If you use a film camera, there is also a film feeding mechanism. Camera is a precision instrument integrating optics, mechanics and electronics. Digital cameras have fully automatic operation functions, such as autofocus and automatic exposure. A simple mechanical camera only has a shutter button and a power switch.

First, the fuselage

When we pick up the camera, the first thing we see is an opaque black box, which we call the fuselage. The fuselage is the general carrier connecting the optical, mechanical and electronic parts of the camera. Its front end is equipped with a camera lens.

Digital camera body is equipped with electronic components such as image sensor, digital image processor and image memory. The camera body of the traditional film camera is filled with film, and various optical, mechanical and electronic components are installed in the middle of the film, so that the camera becomes a whole. In addition, all kinds of photographic accessories and auxiliary equipment should also be connected to the fuselage when used. Therefore, the camera body is generally made of metal or injection molding material with high processing strength.

Second, the lens

A lens is also called a photographic objective. The role of the lens is to make the external scene form a clear image on the film plane in the camera black box. Just like our human eyes can clearly reflect what we see on the retina to our eyeballs. Lens is an important part of a camera. Students should love the camera as much as their own eyes.

If you look closely, you will find that there are several convex and concave lenses in the lens, which we call positive and negative lenses. The positive (convex) lens converges light to produce a real image, while the negative (concave) lens scatters light to produce no real image. The combination of positive and negative lenses can not only make the formed image clear, but also reduce the aberration and improve the imaging quality. Therefore, all camera lenses are composed of different numbers of positive and negative lenses. The more advanced the lens, the more lenses. Lenses usually consist of 3 groups of at least 4 lenses. Lenses are usually made of finely ground optical glass with a coating on the surface.

There are many kinds of modern camera lenses. Digital cameras usually use EF electronic zoom lens with motor to automatically adjust the focal length of the lens, which greatly facilitates the photographer's creation and meets the needs of different photographers.