What does a SLR camera mean?

a DSLR Digital camera refers to a Single-Lens Reflex digital camera, that is, digital, single camera, lens lens and reflex reflex reflex. Representative models in the market are common in Nikon, Canon, Pentax, Fuji and so on.

Working principle:

In the working system of a SLR digital camera, after the light reaches the reflector through the lens, it refracts to the focusing screen above and forms an image. Through the eyepiece and the pentaprism, we can see the scenery outside in the viewing window. In contrast, general digital cameras can only see the captured images through LCD screen or electronic viewfinder (EVF). Obviously, the image directly seen is more conducive to shooting than the image seen through processing.

when shooting in DSLR, when the shutter button is pressed, the reflector will bounce up, and the shutter curtain in front of the photosensitive element (CCD or CMOS) will be opened at the same time, and the light passing through the lens will be projected onto the photosensitive original, and then the rear reflector will be restored immediately, and the image can be seen again in the viewing window. This structure of the single-lens reflex camera ensures that it is shot through the lens, which can make the image seen in the viewing window always the same as that on the film, and its framing range is basically the same as the actual shooting range, which is very conducive to intuitive framing and composition.

second, it is different from ordinary digital cameras.

1. The structure is different. DSLR Digital camera refers to Single-Lens Reflex digital camera, that is, digital digital, single camera, lens lens and reflex reflex reflex. Single-lens reflective structure refers to the use of the mirror in the lens to reflect the light from the lens to the pentaprism above the camera. After many reflections and refractions, it forms a mirror image that is the same as the real thing, eliminating the parallax effect, thus improving the shooting effect. This structure is not available in most ordinary cameras. This is the main difference between SLR cameras and other digital cameras.

2. Another great feature is that you can exchange lenses of different specifications (wide angle, telephoto, etc.), which is an inherent advantage of SLR cameras and incomparable to ordinary digital cameras. From this point of view, "digital SLR" can be simply understood as those digital cameras that can "change lenses".

3. Different user groups. SLR digital cameras are located in high-end products and belong to professional models, while other digital cameras are generally used for home use, so they are also called consumer models. The area of SLR digital photosensitive element (the most important component related to the photographic quality of digital cameras) is much larger than that of ordinary household digital cameras, which makes the photosensitive area of each pixel of SLR digital cameras far larger than that of ordinary household digital cameras, so each pixel can show more detailed brightness and color range, which makes the photographic quality of SLR digital cameras significantly higher than that of ordinary household digital cameras. At the same time, compared with ordinary household digital cameras, digital SLR cameras have larger dynamic range (signal-to-noise ratio), interchangeable lenses, better imaging quality, shorter shutter lag, faster operation and processing speed, which is incomparable to household DC in terms of framing, continuous shooting speed and professional control.

SLR refers to single lens reflex, that is, SLR(Single Lens Reflex), which is the most popular viewfinder system today, and most 35mm cameras use this viewfinder. In this system, the unique design of reflector and prism enables the photographer to directly observe the image passing through the lens from the viewfinder. Therefore, you can accurately see the same image that the film is about to "see". The heart of the system is a movable mirror (as shown in the light blue part), which is placed in front of the film plane at a 45 angle. The light entering the lens (as shown in the red light path) is reflected upward by the reflector to a piece of ground glass. Early SLR cameras had to hold the camera in a waist-level way and look down at the ground glass. Although the image on the ground glass is upright, it is upside down. In order to correct this defect, the current eye-level SLR camera is equipped with a pentaprism above the ground glass. This kind of prism reflects the light many times to change the light path, and sends the image to the eyepiece. At this time, the ground image is upright up and down and corrected left and right. When framing, most of the light entering the camera is reflected upward by the reflector to the pentaprism. Almost all the shutters of SLR cameras are directly in front of the film (it is called the focal plane shutter because it is located in the film plane). When framing, the shutter is closed and no light reaches the film. When the shutter button is pressed, the reflector quickly turns up to get out of the way, and at the same time, the shutter is opened, so the light reaches the film and the shooting is completed. Then, the mirror in most cameras will be reset immediately.

This necessary tilting action of the mirror also brings some other problems:

First, the viewfinder will be blocked at the moment of taking a photo. Because the time of being blocked is only a flash, this is not a major problem for the mirror that is reset immediately. However, it also raises some contingency problems. For example, when using stroboscopic shooting, you will not be able to see whether the stroboscopic device flashes normally through the viewfinder.

second, the noise of the mirror movement. This may become an important problem in places where quiet is needed. Because there is no moving mirror that suddenly blocks the light path in the ranging camera, this noise will not be generated.

third, the vibration of the camera, that is, the overall movement of the camera caused by the tilting action of the mirror. Suppose you shoot with a shutter speed of 1/5 second, so don't worry. This vibration will not be detected. However, if you take an accurate photo at a low shutter speed, such as shooting with a telephoto lens in weak light, this vibration may be very problematic for imaging.

in addition, there is another problem in using SLR for framing. For example, we want to shoot with a small aperture like f/32, and the light allowed into the lens by f/32 is very weak, which will lead to the dim image seen in the viewfinder, which may be difficult to focus or even impossible to focus at all.

In fact, the solution of SLR is quite ingenious. It will first use the maximum aperture of the lens to complete the framing and focusing. When the shutter is pressed, the aperture of the lens will immediately shrink to the preset aperture to complete the film exposure. At the moment when the exposure is completed, the aperture will be opened to its maximum aperture to prepare for the next shooting.

1. Several reasons for choosing digital SLR:

The professional positioning of digital SLR cameras determines that even popular products for ordinary users and enthusiasts have a lot of advantages, which is the fundamental reason why many enthusiasts choose digital SLR cameras. We can sum up the professional characteristics of digital SLR as follows:

1. Advantages of image sensor

For digital cameras, the photosensitive element is one of the most important core components, and its size directly affects the shooting effect. In order to achieve good shooting effect, the most effective way is not only to increase the number of pixels, but also to increase the size of CCD or CMOS. Whether using CCD or CMOS, the sensor size of digital SLR cameras is far more than that of ordinary digital cameras. Therefore, the number of sensor pixels of digital SLR is not only relatively high (at present, the minimum is 6 million), but also the area of a single pixel is four or five times that of a civil digital camera, so it has an excellent signal-to-noise ratio and can record a wide brightness range. The image quality of a 6-megapixel digital SLR camera definitely exceeds that of an 8-megapixel digital camera with a 2/3-inch CCD.

2. Rich lens selection

As a product of optical, mechanical and electrical integration, the performance of the optical imaging system is also very important to the final imaging effect. Having an excellent lens is no less significant for imaging than the choice of image sensor. At the same time, with the cost of image sensor, image engine and storage device decreasing, the proportion of optical lens in the cost of digital camera is also increasing. This is especially true for digital SLR. In the choice of traditional SLR cameras, the richness of lens group and the imaging quality are important factors in the choice of film friends. In the digital age, the retention rate of lens group has naturally become the basis of brand competition. Canon, Nikon and other brands have a huge autofocus lens group, from super wide angle to super telephoto, from macro to soft focus, users can choose matching lenses according to their own needs. At the same time, due to the large sensor area, it is easier for digital SLR cameras to get excellent imaging. More importantly, many photography enthusiasts generally have one or two or even more than a dozen professional lenses, which are purchased by cinematographers with their hard-earned money. If they buy a digital SLR camera body, they will revitalize the lens at once, and they will form two complementary film and digital systems with the original traditional film camera.

3. Quick response speed

One of the biggest problems of ordinary digital cameras is that the shutter lag is long, and if you don't master it well, you will often miss the most wonderful moment. Response speed is the advantage of digital SLR. Because its focusing system is independent of imaging devices, they can basically achieve the same response speed as traditional SLR, which makes users handy in news and sports photography. At present, both Canon's EOS1D MARKⅡ and Nikon D2H can reach the continuous shooting speed of 8 frames per second, which is comparable to traditional film cameras.

4. Excellent hand control ability

Although the camera's automatic shooting function is getting stronger and stronger, a user who has certain requirements for photography will not be satisfied with shooting in automatic mode because of the ever-changing environment and the situation of the subject. This requires that digital cameras also have the ability of manual adjustment, so that users can adjust according to different situations to achieve the best shooting effect. Therefore, the function of manual adjustment has become a necessary function of digital SLR, and it is also a professional representative. Exposure and white balance are two important aspects in many manual functions. When the automatic metering system can't accurately judge the light and color temperature of the shooting environment, users need to judge according to their own experience, and make mandatory adjustments manually to achieve good shooting results. This is also the embodiment of the professionalism of digital SLR. For example, EOS1D can adjust the color temperature value based on 1K each time to help users get the best effect.

5. Abundant accessories

An important difference between a digital SLR and an ordinary digital camera is that it has strong expansibility. In addition to continuing to use additional lenses such as polarizers and interchangeable lenses, it can also use professional flashlights and other auxiliary equipment to enhance its ability to adapt to various environments. For example, high-power flash, ring-shaped macro flash, battery handle and timing remote control, these rich accessories make digital SLR adapt to various unique needs, while ordinary digital cameras are greatly inferior.