Detailed working principle of SLR camera

Principle of SLR (Single Lens Reflex Camera) The full name of SLR is single lens reflex camera. At present, there are 135 and 120 SLR on the market. SLR is to make up for many defects of TLR (dual lens reflex camera) and paraxial camera. It uses the same lens for framing and shooting (so it is also called TTL framing, through the lens), and its design basically avoids the parallax problem of framing. Advantages and disadvantages of SLR: Advantages: the same lens is used for framing and shooting, and the framing is accurate, basically ignoring the differences; Disadvantages: during the exposure process, the reflector rises and the picture cannot be seen; The up-and-down movement of the mirror is the main source of fuselage vibration. Several key components of SLR are: 1, reflector: the function is to reflect the image used for framing to the focusing screen through the photographic lens; The reflector is a piece of glass with silver reflective material on the surface (note that it is on the back of the glass unlike a mirror, so try to wipe the reflector as little as possible when maintaining the camera, even if there is dust on the mirror, it will not affect the imaging), and the 45 hinge is in the reflector box. Before exposure, the function of the reflector is to change the light path and reflect it into the viewfinder, so that the operator can view and focus correctly. Before the shutter is opened, the reflector turns up to make way for the light path, then the shutter is opened and the light reaches the film plane for exposure. After the exposure process, the mirror immediately returns to its original position, that is, the instantaneous mirror. 2. Focus screen: the function is to check the focus. The focusing screen is equivalent to the ideal film plane, that is, the distance from the mirror to the focusing screen is equal to the distance from the mirror to the film plane. Fresnel lenses, usually ground glass, are used to focus rather than the film plane before exposure. When the focus is accurate, a clear image will appear on the focus screen. Due to the principle of optical reflection, the picture on the focusing screen is reversed from left to right, which can only be corrected by the five-sided viewfinder; 3. Pentagon viewfinder: its function is to correct the left and right reflections on the focusing screen, so that the image seen by the viewfinder is exactly the same as the direction of the scene directly seen.

A pentagonal prism is usually cut and polished by a whole piece of solid glass, and then the outer surface (except the two surfaces connected with the focusing screen and the viewfinder eyepiece) is coated with reflective materials to form a specular reflection inside. The viewfinder has two main indicators: viewfinder magnification (viewfinder magnification for short) and viewfinder range. The magnification of the viewfinder refers to the ratio of observing the opening angle of the subject to the eyes through the viewfinder to directly observing the opening angle of the subject to the eyes, that is, the ratio of the size of the subject seen through the viewfinder to the size of the subject directly seen with the eyes. The magnification of framing is large, the viewing angle is small, and the scenery seen during framing is close to the original object, with strong sense of reality; The framing magnification is small and the viewing angle is large, so it is easy to see the panorama when framing. If the magnification is too small, it is difficult to observe the details of the object, which is not conducive to composition and focusing, and there is a great difference between the object and the image, which makes it very uncomfortable to take pictures. The magnification is generally less than 1X, mostly between 0.75 times and 0.95 times ... The field of view refers to the ratio of the scene range seen through the viewfinder to the scene range shot by the bottom film, expressed as a percentage. Generally, the picture seen from the viewfinder is not completely the shot picture, but always smaller than the shot picture, generally 90% ~ 100%. Therefore, SLR only basically avoids parallax, and only the framing range of 100% can be called no framing parallax. Usually only professional models have a visual range of 100%. SLR is short for single-lens reflex camera.

Generally, a camera takes a view through a single small lens, so the manufacturing process is relatively simple and the cost is low, so the price is relatively cheap. However, there is a certain level difference between what the eyes see and the image that falls on the film (the digital camera is on the photosensitive element).

The design of a single-lens reflex camera is to divide the image obtained by the lens into the viewfinder when framing, so that the image seen in the viewfinder is consistent with the image falling on the film, and there is no phase difference. However, the design process of SLR camera is complicated.

It's not surprising that you said that a 5 megapixel camera is more expensive than a 7 megapixel camera. If the former is more complicated than the latter in the production process, the above phenomenon will occur. In addition, the established brand effect will also cause famous brands to be more expensive than miscellaneous brands. In terms of materials, such as the same Chinese cabbage, it is more expensive to make it with meat than with vermicelli. The full name of SLR is single-lens reflection, and SLR camera is a camera that uses single-lens reflection to obtain images of objects for observation and shooting. The viewfinder of a SLR camera is called TTL (through lens) SLR viewfinder. This is the only way to find scenery on a professional camera, and it is also an optical viewfinder that really has no error and passes through the lens. The viewfinder can reach 95% of the real shot. The only drawback is that if the lens is too small, the viewfinder will darken, which will affect the manual focusing. Fortunately, now everyone has autofocus, which is no longer a big problem. Of course, if TTL SLR viewfinder is used, in order not to make the viewfinder too dark, manufacturers will use large-caliber advanced lenses, so the lenses of SLR cameras are generally large at present, which is caused by this factor. Conclusion: The influence seen from the viewfinder is through primary reflection (mirror) and secondary total reflection (pentagonal mirror).

CCD obtains image information when the mirror bounces up at the moment of shooting, and then opens the shutter for exposure. For cameras, SLR is more convenient and practical to operate.

Imaging is finer than advanced manual DC.

SLR means that the light shines directly on the viewfinder and is not reflected by the prism!

Less light loss!

Even without changing the lens, the advantages of SLR are very obvious. One is fast, regardless of starting speed and focusing speed. There is also a large CCD size and less noise in photos. SLR is a kind of digital camera which is close to the traditional camera effect.

The full name of SLR camera is single lens reflex camera. More specifically, a SLR camera is a camera that uses a single lens to reflect light to obtain images of objects for observation and shooting. It is a camera with higher technical content and performance than traditional paraxial cameras and digital cameras. At present, both high-end film cameras and digital cameras adopt the SLR body design with replaceable lenses.

Comparing the working principle of other cameras 1: What is the difference between the imaging principle of SLR digital cameras and ordinary digital cameras?

Single lens reflex (SLR) refers to single lens reflex. In this system, the unique design of the mirror and prism enables the photographer to directly observe the image passing through the lens from the viewfinder. It can be seen from the structural diagram of a single-lens reflex camera that the light passes through the lens and reaches the reflector, and then refracts to the focusing screen above to form an image. Through the eyepiece and pentaprism, we can see the scenery outside in the observation window. When shooting, press the shutter button, the reflector will pop up, and the shutter curtain in front of the film will be opened at the same time. The light (image) passing through the lens will be projected on the film to make the film sensitive, and then the reflector will immediately return to its original state, and the image can be seen in the viewfinder.

2. What are the advantages of SLR digital cameras?

This structure of the single-lens reflex camera ensures that it is shot through the lens, so that the image seen in the observation window is always consistent with the image on the film, and its framing range is basically consistent with the actual shooting range, eliminating the parallax phenomenon of the paraxial head-up framing camera. From the perspective of learning photography, it is very conducive to intuitive framing and composition. Another major feature of a single-lens reflex camera is that it can replace lenses with different specifications.