What is a SLR camera?

Single-lens reflex (SLR) refers to single-lens reflex, and SLR camera is a camera with this function. This is the most popular viewfinder system, which is used by most 35mm cameras. 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. Therefore, you can accurately see the same image that the film is about to "see".

SLR camera-mirror

The heart of a SLR camera is a movable mirror, which is placed in front of the film plane at an angle of 45. The light entering the lens is reflected upward by the mirror to a piece of ground glass. Early SLR cameras had to hold the camera waist-high 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 cameras are equipped with a pentaprism above the frosted glass. This prism reflects light many times to change the light path and send 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. Shutters of SLR cameras are almost always directly in front of the film (because they are located in the film plane, they are called focal plane shutters). When framing, the shutter is closed and no light reaches the film. Press the shutter button, the reflector quickly turns up to get out of the way, at the same time, the shutter opens, the light reaches the film, and the shooting is completed. Then, the mirrors in most cameras will be reset immediately.

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

First, the viewfinder will be blocked at the moment of taking pictures. Because the shielding time is only a moment, this is not a big problem for the image that is reset immediately. However, it also raises some emergency issues. 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 moving. This may become an important problem where silence 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 at a shutter speed of 1/500 seconds, don't worry. This vibration will not be detected. However, if you take accurate photos at a low shutter speed, such as with a telephoto lens in low light, this vibration may cause great problems in imaging.

In addition, there is another problem with SLR framing. For example, if we want to shoot with a small aperture like f/32, the light allowed into the lens by f/32 is very weak, which will cause the image seen in the viewfinder to be blurred, and it may be difficult to focus or even impossible to focus at all. In fact, the solution of SLR is quite clever. 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 the maximum aperture to prepare for the next shooting.

Difference from digital camera

In the working system of SLR digital camera, after the light reaches the reflector through the lens, it 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. In contrast, ordinary digital cameras can only see the captured images through the LCD screen or electronic viewfinder (EVF). Obviously, the directly seen image is more conducive to shooting than the processed image. When shooting in DSLR, press the shutter button, the reflector will pop 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 in the viewfinder. This structure of the single-lens reflex camera ensures that it is shot through the lens, so that the image seen in the viewfinder is always consistent with the image on the film, and its framing range is basically consistent with the actual shooting range, which is very conducive to intuitive framing and composition.

A major feature of SLR digital cameras is that they can change lenses of different specifications, which is an inherent advantage of SLR cameras and incomparable to ordinary digital cameras. In addition, SLR digital cameras are now positioned in the high-end products of digital cameras, so the area of photosensitive elements (CCD or CMOS) related to the photographic quality of digital cameras is much larger than that of ordinary digital cameras, which makes the photosensitive area of each pixel of SLR digital cameras much larger than that of ordinary 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 digital cameras.

Manual control ability of SLR camera

Although the camera's automatic shooting function is getting stronger and stronger today, a user who has certain requirements for photography will not be satisfied with shooting only in automatic mode because of the ever-changing environment and shooting objects. 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 an essential function of digital SLR and a professional representative. Exposure and white balance are two important aspects in many manual functions. When the automatic metering system cannot 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, EOS 10D can adjust the color temperature value on the basis of 100K every time to help users get the best effect.

SLR technology

First of all, let's learn what a digital SLR camera is. To put it bluntly, a digital SLR camera is a digital camera adopting new SLR technology. As a professional digital camera, the photos taken with it are incomparable in definition and quality. These are the high performance of digital SLR cameras made by SLR technology.

Single lens reflection. The camera using this technology has only one lens, which is responsible for photography and framing. This can basically solve the problem of poor photo quality caused by parallax. Moreover, when a SLR camera is used to view a scene, the light emitted by the object is focused by the lens, reflected by the inclined reflector to the focusing screen for imaging, and then reflected by the "roof prism" raised at the top. Photographers can observe the scene through the viewfinder eyepiece, and it is the same image as the scene, which is convenient for framing and focusing. When shooting, the mirror will bounce up immediately, the lens aperture will automatically shrink to a predetermined value, and the shutter will open to make the film sensitive; After exposure, the shutter is closed and the aperture of the mirror and lens is reset at the same time. This is the SLR technology in cameras. Now digital cameras have become professional digital SLR cameras after adopting this technology. The single-lens reflective framing method basically means professional positioning, which also doomed the professional road of digital SLR cameras. Even products for ordinary users and enthusiasts have many advantages.