How does a camera work?

Photographic cameras have undergone many changes from the past century and a half until today, and what we see today as modern examples is the result of countless years of efforts to It is a development of this device, but nevertheless it is interesting to know that the basic principles of operation of all of them are the same! Therefore, in this article, we go to an interesting question: How does a camera work?

The role of light in the operation of a camera

If you decide To understand the mechanism of the camera, first of all, we must know how light works, because without understanding light, there will be no photography. In this section, without wanting to drown too much in the wild world of physics, we will clarify the basic principles of light for you.

As you know, light travels in a straight path and can be reflected or absorbed. To the human eye and camera, light is perceived as a wave, and this property appears almost identical to sound waves, except that they differ in wavelength, frequency, amplitude, and energy level. In this regard, the duty of a photographer is to collect and capture light according to his taste and desired shape.

1. Getting to know the camera lens and its importance in recording images

Apart from the world's first photographic cameras that did not have glass, the two main parts of this device include the lens and the light detector. In general, a camera lens collects light and projects it onto a light-detecting surface, usually photographic film or a digital sensor. Then, through various processing methods, you will get your final image that is shaped according to your taste. In fact, the act of photography is all that happens between these stages and even before it, and you, as a photographer, must have control over it.

The camera lens is the first part of this device that encounters light. Light passes through the lens and creates the way the image is displayed through various optical formulas. It is interesting to know that the lens of your camera is not actually a single lens, but this device is made of several different lenses in the form of a group! In general, the current structure is the result of continuous and accurate design and tests, which are set with standard optical formulas such as 50mm f/1.8 or f/1.4 for various lens models. It is interesting to know that some advanced camera lenses follow formulas that were not possible to design until recently.

But what is the significance of these formulas? In general, the optical formula in a lens determines the image it can project onto a sensor.

Photographic camera lens structure

The importance of focal length

In simple words, focal length is a characteristic that determines the amount of magnification. A shorter focal length displays a wider angle of view while a longer focal length provides a narrower slice of the scene. In technical terms, the focal length is the distance between the point of convergence of the lens and the sensor or film.

Scientifically It is practically impossible to design a lens with a point of convergence before the front of the device, but this point can be placed behind it. This means that telephoto lenses (with the exception of mirror lenses) must be longer.

However, wide-angle lenses (the ones you usually see in wildlife photography) can be surprisingly long in length. Special zoom lenses can change their point of convergence forward and backward. Prime lenses have a fixed point and the elements only move to focus.

Aperture

The diameter of the lens determines the maximum amount of light it can pass through. In most lenses, there is a part called the iris, which is used to narrow the diameter of the lens. This part works just like the pupil of the human eye, meaning that the narrower it is, the less light enters the eye or lens. Also, with a narrower iris, you get a deeper depth of field and less background separation.

The aperture ratio value is expressed as an F-stop, which can be calculated by dividing the focal length by the diameter of the lens (at the iris). Calculated. For example, F-stop is a 50mm lens with an aperture diameter of 25mm, f/2.

The importance of the opening of the aperture in the photography process

Of course, keep in mind that when you zoom, the focal length changes, as a result the aperture ratio also changes. Of course, in lenses with a fixed minimum aperture value, for example, 24-70mmf/2.8, it is possible to zoom and keep the aperture ratio constant by gradually opening the aperture.

Ability to focus

Just like the human eye, the camera lens sees the world in focal planes. These focal planes are parallel to the front of the camera lens and (in most cases) to the sensor. An exception to this is tilting lenses with a very wide angle of view. In general, in order to focus on a particular plane, one of the lens elements must move within it. You can control this element with autofocus or manually by turning the focus ring. In such a case, the closer the focus section is to the sensor, the more the focus will be on the intended subject.

Except for macro lenses, most lenses on the market can go to infinity focus. Of course, although you can physically focus as much as you want, you should know that such an action is not logical, because after a certain limit, the image may become blurred. When shooting close-up, the focus element moves away from the sensor. Therefore, any non-macro lens can be turned into a macro lens by adding extension tubes between the body and the lens.

In the same way, if you are interested in macro photography, you can turn it into a special camera for macro photography using special and high-quality lenses.>

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Shake Stabilizer

On some modern lenses, you may find a device that actively stabilizes camera shake. This part usually consists of a distinct structure behind the lens. The naming of stabilizer systems is different from one brand to another. For example, Canon calls them IS ("Image Stabilizer"), Nikon calls it VR ("Vibration Reduction") or Sony OSS ("Optical SteadyShot").

Weight and ergonomics of lenses

The size and weight of lenses depends on many factors, as a faster aperture usually means a larger lens. Also, the wide zoom range results in the lens becoming longer when zooming in, but it should be noted that most of these models are collapsible. The larger the size of the desired sensor, the larger the lens should be.

2. Photographic camera and its role in image recording

As mentioned, the light reaches the camera after passing through the lens, where it is detected by a sensor or film.

Viewfinder ( Viewfinder)

All DSLRs and many mirrorless cameras have a viewfinder. This part can be optical or electronic. In a digital DSLR camera with an optical viewfinder, when light passes through the lens it hits a semi-transparent mirror and then most of the light is reflected back to the pentaprism and then the viewfinder.

During the same path, some of the light is also reflected down through a secondary mirror to the autofocus sensor.

How the viewfinder works in a photography camera

In mirrorless cameras, there is no optical connection between the lens and the human eye, and light always shines directly. reaches the sensor. Then the desired view is transferred digitally from the sensor to the electronic viewfinder (EVF) or to the back panel.

Shutter in a camera

Shutter is a mechanism that releases light for a certain time (shutter speed) to the film or sensor. Before the age of digital cameras, the only option available to photographers was a mechanical shutter, which, as you may have seen in movies, moved an obstacle in the path of light. The light shines on it. At the time of shooting, this curtain is removed and the light reaches the film or image receiver during the set time and is closed again.

Rolling mechanical shutter found in most cameras has two screens; When you press the shutter button, the first curtain slides up, allowing light to reach the camera's sensor, then after a set amount of time, the second curtain closes, blocking the sensor again. One of the disadvantages of the mechanical rolling shutter is that you cannot use a standard flash below a certain shutter speed, in this case the entire frame is not exposed at the same time. This time is about 1/200 second!

Electronic shutters are a product of The era of digital cameras are used for fast and continuous image reading. The electronic rolling shutter is found in almost every digital camera and works by collecting data from the sensor (usually rows of pixels). By using these types of shutters, silent photography is provided with a very low shutter speed, in some cases up to 1/32000 seconds. The negative point is that in this situation, subjects that move quickly will suffer from distortion due to asynchronous reading of data.

Sensor

In general, digital sensors are composed of pixels, and Both are made of small solar cells that convert light into electricity. Most digital cameras have a standard single layer CMOS or CCD sensor. CMOS is a newer technology that allows the readout of individual pixels with low power consumption. It is interesting to know that the pixels are arranged in an arrangement called "Bayer mosaic" using color filters. Bayer mosaic consists of blocks of four pixels, two green, one red and one blue. Since each pixel is only sensitive to its own color, the end result is an image with scattered red, green, and blue dots.

Bayer makeup

Note that the number of green pixels in this system is double the number of red and blue because the human eye compared to Blue or red light is more sensitive than green light. An abundance of green pixels creates an image that appears to have less noise and more detail.

ISO

In very simple terms, ISO is a camera setting that brightens or darkens photos. It will be you. When you adjust the ISO value with your camera, different things can happen on the device, depending on your camera and the exact ISO value. Cameras with CMOS sensors (in most digital cameras) have a small amplifier for each pixel, so after the frame is exposed, the pixels are amplified to a higher level according to the ISO set on the camera. Therefore, this issue helps you to take pictures in low-light environments.

Digital camera conversion and processing

After reading the information from the digital camera sensor and passing through the amplifiers, the data to Digital data is converted. This is the function of the analog to digital converter. Most modern cameras convert data to 16-bit digital data, but only use 14 bits. In fact, those 2 extra bits provide more flexibility in post-processing and filtering the information.

14 bits means that there are 16,384 possible values for each pixel, this range of values for pixels is a factor. To create a wide color spectrum and provide high color tonality in modern digital cameras. After this step, the pixel data goes to the image processor, and if you choose jpg output, the processor performs several algorithms, filters, and compression operations on the data to get what you want.

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Source: EXPERT PHOTOGRAPHY