Table of contents:
- The structure of the camera
- Why you need a lens
- How a lens works
- The principle of operation of the first camera
- The difference between SLR cameras
- Focus on the object
- Sizelens and photo size
- Differences between lenses
- Chromatic aberration
- Film and image sensors
- Why megapixels matter
- How Polaroid works
Photography is one of the most important inventions in history - it really changed the way people think about the world. Now every person can see images of things that are actually at a great distance or have not existed for a long time. Every day, billions of photos are posted online, turning life into digital pixels of information.
The structure of the camera
Photography allows you to capture important moments of life and save them for years to come. Devices for creating images have long been built into phones and other gadgets, but the principle of operation of the camera remains a mystery to many. Photography is as much a science as it is an art, but the vast majority are unaware of what happens when they press the camera button or open the smartphone camera app. The first camera, the structure and principle of which will be discussed later, had no buttons at all and did not at all resemble an application. But his device is at the heart of modern gadgets.
For example, a film camera consists of three main elements: optical - lens, chemical - film, and mechanical - camera body. Let's briefly consider the principle of operation of the camera: the film is loaded into a spool on the right and wound onto another spool on the left, passing in front of the lens along the way. It is a long strip of flexible plastic coated with special chemicals based on light-sensitive silver compounds.
Black and white film has one layer, and color film has three: the top is sensitive to blue light, the center is sensitive to green, and the bottom is sensitive to red. The image was obtained due to the chemical reaction of each of them. So that the light does not spoil the film, it is wrapped in a durable light-resistant plastic cylinder, which is placed inside the camera. But how does it combine all the components so that they record a clear, recognizable image? There are many different ways to make these parts work, but first you need to understand the basic principle of how a camera works. Since photography does not require electricity, a conventional single-lens mirrorless camera is an excellent illustration of the basic processes of photography.
Why you need a lens
It's best to briefly start explaining how a camera works with theory. Imagine that you are standing in the middle of a room with no windows, doors or lights. Nothing can be seen in such a place because there is no light source. Assuming you took out your flashlight and turned it on, andthe beam from it moves in a straight line. When this light hits an object, it bounces off it and hits the eyes, allowing you to see what's inside the room.
The principle of operation of a digital camera is similar to the process of snatching objects from a dark room with a beam from a flashlight. The optical component of the camera is the lens. Its job is to bounce the rays of light coming back from the subject and redirect them so they come together to form an image that looks like the scene in front of the lens. It may not be entirely clear how this process occurs and why ordinary glass is able to redirect light. The answer is very simple: when light moves from one medium to another, it changes speed.
How a lens works
Light travels faster through air than through glass, so the lens slows it down. When the rays hit it at an angle, one part of the wave will reach the surface before the other and thus slow down first. When light enters the glass at an angle, it bends in one direction and then again when it exits the glass because parts of the light wave hit the air and accelerate before others.
A standard convex lens has one or both sides of the glass curved. This means that passing light rays will be deflected towards the center of the lens as they enter. In a double convex lens, such as a magnifying glass, light will bend as it enters as it exits. This effectively changes the path of light from the object, which is related to the mainthe principle of operation of the camera. The light source emits light in all directions. All rays begin at one point and then constantly diverge. A converging lens takes these rays and redirects them so that they all converge back to the same point. In this place, the image of the subject is obtained.
The principle of operation of the first camera
The first cell was a room with a small hole in one side wall. Light passed through it and was reflected in straight lines, and the image was projected upside down on the opposite wall. It was called the camera obscura and was used by artists to paint artistic canvases. The invention is attributed to Leonardo da Vinci. Although such devices had existed long before the first real photograph, it was not until someone decided to place light-sensitive material in the back of this room that the idea of obtaining an image in this way was born. The principle of operation of the first camera was as follows: when the beam hit the photosensitive material, the chemicals reacted and etched the image on the surface. Since this camera did not capture too much light, it took eight hours to take one photograph. The image also came out quite blurry.
The difference between SLR cameras
Professionals often prefer SLR cameras. It is believed that the quality of the picture is better because the photographer sees the real image of the subject in the viewfinder, notdistorted by digitization and filters. If we briefly describe the principle of operation of a camera with a reflex viewfinder, then the meaning boils down to the fact that in such a camera the photographer sees a real image. It can also adjust all the details by turning and pressing the buttons. This is due to the double mirror - pentaprism. But in the design of the camera there is one more - translucent, located in front of the matrix, which is also called a sensor or sensor. The principle of operation of the camera shutter is that when a button is pressed, it raises the mirror and changes its angle of inclination. At this moment, a stream of light hits the sensor, after which the image is processed and displayed on the screen.
The principle of operation of a SLR camera is connected with the diaphragm, which gradually opens up to let the rays through. It consists of petals, the position of which determines the diameter of the central circle and the amount of light transmitted. The beam hits the lenses, and then on the mirror, focusing screen and pentaprism, where the image is flipped, and then on to the viewfinder. This is where the photographer sees the real image. The principle of operation of a mirrorless camera is different in that it does not have such a viewfinder. Often it is replaced by a screen or electronic version. Phase autofocus is also only available on SLR cameras. Another difference is that when you press the shutter button, the light immediately hits the camera matrix.
Focus on the object
Image quality changes depending on how light passesthrough the camera lens. It is related to the angle at which the light beam enters it and what its structure is. This path depends on two main factors. The first is the angle at which the light beam enters the lens. The second is the structure of the lens. The light entry angle changes as the object moves closer or further away from it. Rays that enter at a sharper angle will exit at a more obtuse angle, and vice versa. The camera lens captures all reflected light rays and uses glass to redirect them to a single point, creating a sharp image. The overall "bending angle" at any particular point remains constant.
If the light is out of focus, the image will look blurry or out of focus. Essentially, bending a lens increases the distance between different points on it. Rays from a closer point converge farther away from the lens than from one farther away. That is, the real image of a closer object is formed farther from the lens than from a more distant one. The overall "bow angle" is determined by the structure of the lens. The camera lens rotates to focus by moving closer or further away from the surface of the film or sensor. A lens with a more round shape will have a sharper angle of curvature. This increases the amount of time that one part of the light wave travels faster than the other part, so the light makes a sharper turn. As a result, the in-focus real image is formed farther from the lens when the lens has a flatter surface.
Sizelens and photo size
As the distance between the lens and the real image increases, the light rays expand to form a larger image. A flat lens projects a large image, but the film is only exposed in the middle of the image. Essentially, the lens is centered in the middle of the frame, magnifying a small area in front of the viewer. As the front of the glass moves away from the camera sensor, objects get closer. Focal length is a measurement of the distance between where light rays first hit the lens and where they reach the camera's sensor. Professional cameras allow you to install different lenses, with different magnifications. The degree of magnification is described by the focal length. In cameras, it is defined as the distance between the lens and the real image of an object at a far distance.
Differences between lenses
A higher number of focal lengths indicates a larger image magnification. Different lenses are suitable for different situations. If you shoot a mountain range, you can use a lens with a particularly large focal length. They allow you to focus on certain elements in the distance. If you need to take a close-up portrait, then a wide-angle lens will do. It has a much shorter focal length, so it compresses the scene in front of the photographer.
A camera lens is actually several lenses combined into one block. One converging lens can formreal image on film, but it will be distorted by a number of aberrations. One of the most significant distortion factors is that different colors of the spectrum bend differently as they move through the lens. This chromatic aberration essentially creates an image where the tones are not aligned correctly. Cameras compensate for this by using multiple lenses made from different materials. Each lens processes colors differently, and when they are combined in a certain way, the colors are rearranged. A zoom lens has the ability to move various elements of the lens back and forth. By changing the distance between individual lenses, you can adjust the magnification power of the lens as a whole.
Film and image sensors
The device and the principle of operation of the camera are also associated with recording information on the media. Historically, photographers have also been a kind of chemist. The film consists of photosensitive materials. When these materials are hit by light from a lens, they capture the shape of objects and details, such as how much light is coming from them. In a dark room, the film was developed, subjected to a series of chemical baths, to produce an image. The principle of operation of a camera with a sensor is somewhat different from the operation of a film camera. Although the lenses, methods, and terms are the same, a digital camera sensor looks more like a solar panel than a strip of film. Each sensor is divided into millions of red, green and blue pixels or megapixels. When light hits a pixel, a sensor converts it into energy, and a computer built into the camera reads how much energybeing produced.
Why megapixels matter
The principle of the camera sensor is to measure how much energy each pixel has and allows it to determine which areas of the image are bright and dark. And because each pixel has a color value, the camera's computer can judge the colors in the scene by looking at what other nearby pixels are registered. By bringing together information from all the pixels, the computer is able to approximate the shapes and colors of the object being photographed. If each pixel collects light information, then camera sensors with more megapixels can capture more detail.
This is why manufacturers often advertise megapixel cameras by adding a brief explanation of how the camera works. While this is true to some extent, sensor size is also important. Larger sensors will collect more light, which will help you get better image quality in low light. Packing a lot of megapixels into a small sensor actually degrades image quality because the individual pixels are too small. The standard lens of the 50mm lens does not allow much zooming in or out, making it ideal for subjects that are not too close or too far away.
How Polaroid works
A portable photo studio that captures almost instantaneous images has been a dream for a long time. Until there was an unusual camera that allows you not to wait weeks for printoutsimages. Edwin Land created the first Polaroid camera. He had an idea for instant photography and asked Kodak for funding. But the company took it as a joke and only laughed at him. Edwin Land went home and started working on other projects to raise money. He created the Polaroid Lens and then invented his famous portable photo studio.
The principle of operation of the Polaroid camera is similar to the mechanism of operation of a conventional film camera, inside of which there was a plastic base coated with light-sensitive silver compound particles. Each blank for a photograph has the same light-sensitive layers located on a plastic sheet. They contain all the necessary chemicals for developing a photo. Under each colored layer is another one, with a dye. In total, there are more than 10 different layers on the card, including an opaque base layer, which is a blank for a chemical reaction. The component that starts the process is a reagent, a mixture of deactivators, alkali, white pigment and other elements. It is in a layer just above the photosensitive layers and just below the image layer.
The principle of operation of the Polaroid camera is that before taking a picture, all the reagent material is collected in the form of a ball on the border of the plastic sheet, away from the photosensitive material. After pressing the button, the edge of the film exits the chamber through a pair of rollers that distribute the reagent material in the centerframe. When the reagent is distributed between the imaging layer and the photosensitive layers, it reacts with other chemical elements. The opaque material prevents light from filtering into underlying layers, so the film is not fully exposed before being developed.
Chemicals move down through the layers, turning the exposed particles of each layer into metallic silver. The chemicals then dissolve the developer dye, so it begins to seep up into the image layer. The areas of metallic silver in each layer that were exposed to the light trap the dyes so they stop moving up. Only paints from unexposed layers will move up to the image layer. Light reflecting off the white pigment in the reagent passes through these colored layers. The acidic layer in the film reacts with the alkali and deactivators in the reagent, resulting in a gradual development of the image. It needs light to fully develop, and usually the photographer pulls out the card to see the final chemistry involved in developing the film.