SLR camera
SLR refers to single lens reflex, that is, SLR (Single Lens Reflex). This is the most popular viewfinder system today. Most 35mm cameras use this viewfinder. . In this system, the unique design of the reflector and prism allows the photographer to directly observe the image through the lens from the viewfinder. Therefore, you can see exactly the same image that the film would "see". The heart of the system is a movable reflector (light blue part in the picture), which is placed in front of the film plane at a 45° angle. Light entering the lens is reflected upward by the reflector onto a piece of frosted glass. Early SLR cameras required holding the camera at waist level and looking down at the ground glass to take the view. Although the image on the frosted glass is upright, the left and right sides are upside down. To correct for this flaw, today's eye-level SLR cameras have a pentaprism mounted above the ground glass. This kind of prism reflects the light multiple times, changes the optical path, and sends the image to the eyepiece. At this time, the image is upright and corrected left and right. When framing, most of the light entering the camera is reflected upward by the reflector to the pentaprism. The shutter of almost all SLR cameras is located directly in front of the film (because this shutter is located on the film plane, it is called a focal plane shutter). When framing, , the shutter is closed and no light reaches the film. When the shutter button is pressed, the mirror quickly flips up to clear the light path, and the shutter opens at the same time, so the light reaches the film and the shooting is completed. The mirror in most cameras then resets immediately.
This necessary flip-up action of the reflector also brings some other problems:
1. The viewfinder will be blocked at the moment the photo is taken. Since the time of being blocked is only a fraction of a second, this is not a major problem for a reflector that resets immediately. However, some contingency issues arise. For example, when shooting with a strobe flash, you will not be able to see through the viewfinder whether the strobe device is firing normally.
2. Noise from reflector movement. This can be an important issue in locations where quietness is required. Since there is no moving mirror in a rangefinder camera that suddenly blocks the light path, this noise does not occur.
3. Camera vibration is the overall movement of the camera caused by the flip-up action of the reflector. Assuming you are shooting with a shutter speed of 1/500 second, then there is no need to worry. This vibration cannot be noticed. However, this vibration can be problematic when taking an accurate photo at a slower shutter speed, such as when shooting with a telephoto lens in low light.
In addition, there is another problem with using SLR for framing. For example, we want to use a small aperture such as f/32 to shoot, and the light that the aperture f/32 allows to enter the lens is very weak. This will cause the image seen in the viewfinder to be very dim, and it may be difficult to focus, or even not at all. Unable to focus.
In fact, SLR’s solution is quite clever. It will first use the maximum aperture of the lens to allow us to complete framing and focusing. When the shutter is pressed, the aperture of the lens will immediately shrink to the preset aperture, completing the When the film is exposed, the aperture will open to its maximum aperture at the moment the exposure is completed, preparing for the next shot.
1. Several reasons for choosing a digital SLR:
The professional positioning of digital SLR cameras determines that even popular products for ordinary users and enthusiasts have a large number of outstanding features. This is the fundamental reason why many enthusiasts choose digital SLR cameras. We can summarize the professional features of digital SLRs into the following aspects:
1. Advantages of image sensors
For digital cameras, the photosensitive element is one of the most important core components. First, its size is directly related to the shooting effect. To achieve good shooting effects, the most effective way is not only to increase the number of pixels, but more importantly, to increase the size of the CCD or CMOS. Whether using CCD or CMOS, the sensor size of digital SLR cameras far exceeds that of ordinary digital cameras.
Therefore, the sensor number of a digital SLR is not only relatively high (currently the lowest is 6 million), but the area of ??a single pixel is four to five times that of a civilian digital camera. Therefore, it has an excellent signal-to-noise ratio and can record a wide range of brightness. The image quality of a 6-megapixel digital SLR camera definitely exceeds the image quality of an 8-megapixel digital camera using a 2/3-inch CCD.
2. Rich lens selection
As a product that integrates light, machinery and electricity, the performance of the optical imaging system also has a very important impact on the final imaging effect. , having an excellent lens is no less important to imaging than the choice of image sensor. At the same time, as the costs of image sensors, image engines and storage devices continue to decrease, optical lenses account for an increasing proportion of the cost of digital cameras. This is especially true for digital SLR cameras. In the choice of traditional SLR cameras, the richness and imaging quality of the lens group are important factors for movie lovers to choose. In the digital era, the retention rate of the lens group has naturally become the basis for brand competition. . Canon, Nikon and other brands have a huge group of autofocus lenses, from ultra-wide angle to ultra-telephoto, from macro to soft focus, users can choose matching lenses according to their own needs. At the same time, due to the larger sensor area, it is easier for digital SLR cameras to obtain excellent imaging. What's more important is that many photography enthusiasts generally have one or two, or even as many as a dozen, various professional lenses. These are purchased by photographers with their hard-earned money. If you buy a digital SLR camera body, , the lens was instantly revitalized, and it formed a complementary film and digital system with the original traditional film camera.
3. Fast response speed
One of the biggest problems of ordinary digital cameras is the long shutter time lag. If you don't master it well when taking pictures, you will often miss the most exciting moments. Response speed is the advantage of digital SLRs. Since their focusing system is independent of the imaging device, they can basically achieve the same response speed as traditional SLRs, making them very convenient for users in news and sports photography. Currently, both Canon's EOS1D MARK II and Nikon D2H can achieve a continuous shooting speed of 8 frames per second, which is comparable to traditional film cameras.
4. Excellent manual control ability
Although today's cameras are becoming more and more capable of automatic shooting, due to the ever-changing environment and subject conditions during shooting, Therefore, a user who has certain requirements for photography will not be satisfied with just shooting in automatic mode. This requires digital cameras to also have manual adjustment capabilities, allowing users to adjust according to different situations to achieve the best shooting results. Therefore, having manual adjustment function has become a must-have function for digital SLRs and is also a representative of its professionalism. Among the many manual functions, exposure and white balance are two important aspects. When the automatic metering system cannot accurately judge the light conditions and color temperature of the shooting environment during shooting, the user needs to make judgments based on their own experience and make forced adjustments manually to achieve good shooting results. This is also a reflection of the professionalism of digital SLRs. For example, the EOS10D can adjust the color temperature value based on 100K each time to help users get the best results.
5. Rich accessories
An important difference between a digital SLR and an ordinary digital camera is that it has strong scalability. In addition to being able to continue to use additional lenses such as polarizers and replaceable In addition to the lens, you can also use professional flash and other auxiliary equipment to enhance its ability to adapt to various environments. Such as high-power flash, ring macro flash, battery handle, timing remote control, these rich accessories allow digital SLRs to adapt to various unique needs, while ordinary digital cameras are greatly inferior.
Supplementary information:
1. Digital SLR technology
First of all, let us understand what a digital SLR camera is. To put it bluntly, a digital SLR camera is a digital camera that uses SLR new technology. As a professional-grade digital camera, the photos taken with it are unmatched by ordinary cameras in terms of clarity and photo quality. These are SLR technologies that contribute to the high performance of digital SLR cameras.
SLR, that is, single lens reflex. Cameras using this technology have only one lens, which is responsible for both photography and framing. This can basically solve the problem of photo quality degradation caused by parallax. Moreover, when taking a view with a SLR camera, the light from the subject is focused through the lens, reflected by the tilted mirror to the focusing screen, and then reflected by the "roof prism" with a ridge on the top. The photographer can observe the scenery through the viewfinder. , and the top, bottom, left, and right images are the same as the scene, so framing and focusing are very convenient. When taking pictures, the reflector will pop up immediately, the lens aperture will automatically shrink to a predetermined value, the shutter will open to expose the film; after the exposure, the shutter will close, and the reflector and lens aperture will be reset at the same time. This is the SLR technology in cameras. Today's digital cameras use this technology to become professional-grade digital SLR cameras.
The framing method of single-lens reflex cameras basically means professional positioning, which also determines the professional path of digital SLR cameras. Even products for ordinary users and enthusiasts have a lot of advantages.
2. How to choose a digital SLR camera
Is a DSLR (digital single lens reflex camera) necessary for ordinary home players? Digital SLR DSLR is the only pursuit of professional users (journalists, photographers) and enthusiast photography enthusiasts! Compared with DSLR and consumer-grade DC, there is a big gap between the two: DSLR brings greater dynamic range (signal-to-noise ratio), interchangeable lenses, better imaging quality, and shorter shutter lag. , faster operation and processing speed, more realistic framing, faster continuous shooting speed and more professional control, etc... These are unmatched by consumer DC.
The biggest problem is that the size and weight are larger (heavier) than consumer-grade digital cameras. Accessories such as lenses, flash filters, etc. make digital cameras not very convenient to carry. The second problem is that the CCD/CMOS chip of a digital SLR camera is easily contaminated by dust. Olympus's E-1 can remove dust on the surface of the CCD/CMOS chip through an ultrasonic device, but other brands of digital SLR cameras are still sensitive to dust. It is helpless and seriously affects the imaging quality and service life.
Therefore, although quasi-professional digital cameras such as Sony F828/Minolta A2/Fuji S7000 are facing a huge blow from popular SLR digital cameras, they will still have a greater impact because of the convenience of "one lens to travel anywhere". Strong vitality.
1. Metering and exposure In this aspect, although there are some "selling point" differences in technical details, they can be considered to be essentially the same and there is no need to go into detail.
2. Focus speed, shutter lag, and continuous shooting speed. These indicators are very important for news photography, sports photography, wildlife photography, and snapshot photography. For digital SLR cameras, the improvement in performance is accompanied by a sharp increase in price.
3. Body life: The shutter life of a general SLR camera is 50,000 times, the life of a mid-to-high-end SLR camera can reach 80,000-100,000 times, and the life of a professional SLR camera can reach up to 150,000 times. In actual use, if the high-speed continuous shooting function is frequently used, the shutter life will be reduced. The service life of the LCD screen is approximately 1,000 hours. The component that affects the life of a digital SLR camera is also the reflective viewfinder system. Frequent and high-load use can easily cause the failure of the reflective viewfinder system.
4. Body reliability: Advanced cameras will be dustproof, waterproof, and resistant to impact (shock). Due to the metal body and special materials, such cameras can also be quite expensive.
5. Color space In addition to sRGB, which is the standard color space for Windows and inkjet printers, you can also choose Adobe RGB, which is more widely used. The best color space can be selected depending on the purpose of photography.
6. Flash system For professional photographers, flash metering and exposure systems are very important. Each manufacturer has its own unique skills in automating flash systems. There is no best or no best method. The worst, only the most suitable.
7. Lens group The advantage of digital SLR cameras is that they have interchangeable lenses. It is worth paying attention to whether the original lens series support and the products of independent lens manufacturers are rich enough to meet your needs.
8. Does it support W/A read and write acceleration technology? Digital SLR cameras released after the fall of 2003 will support W/A read and write acceleration technology. Using this technology, CF cards can be read and written up to 40 times faster ( 6MB/S) or above.
9. Transmission interface Digital SLR cameras released after the fall of 2003 should have both USB2.0 and 1394 FireWire terminals. Some cameras should also support 802.11b/g, Bluetooth and other wireless network transmission.
10. Photosensitivity and noise suppression Higher sensitivity and better noise suppression are what we are pursuing.
11. Shutter The highest shutter speed and the slowest shutter speed (B door) are two key indicators of the shutter of a digital SLR camera. The reliability and accuracy of the shutter also need to be concerned. The highest flash sync speed is also a measure of whether a digital SLR camera is advanced.
12. Feel, appearance and weight Whether the body design is suitable for your heart and whether it fits your hand are often the most important aspects when deciding to buy a SLR camera. Regardless of price, the size and weight of professional digital SLR cameras are not acceptable to everyone. Amateur digital SLR cameras that are compact and lightweight are more suitable for ordinary people to use.
13. Psychology In the end, psychology is often the decisive factor, and rational consumption is crucial.
Summary: Digital SLR cameras are currently monopolized by a few manufacturers. The principle that you get what you pay for is an absolute truth in the field of digital SLR cameras. In order to meet the needs of high-load and high-intensity professional photography, it is best to choose an expensive digital SLR camera. If it is just a hobby and fun, it is best to choose an affordable model.
Working principle:
In the working system of a SLR digital camera, after the light passes through the lens and reaches the reflector, it is refracted to the focusing screen above and forms an image, which passes through the eyepiece. And the pentaprism, we can see the outside scenery in the picture window. In contrast, general digital cameras can only view the captured images through the LCD screen or electronic viewfinder (EVF). Obviously the image seen directly is more conducive to shooting than the image seen through processing.
When shooting with a DSLR, when the shutter button is pressed, the reflector will pop up, the shutter curtain in front of the sensor (CCD or CMOS) will open at the same time, and the light passing through the lens will be projected onto the camera. The photosensitive original is exposed to light, and then the rear reflector immediately returns to its original state, and the image can be seen in the viewing window again. This structure of a single-lens reflex camera determines that it is completely focused and photographed through the lens. It can make the image seen in the viewing window always the same as on the film. Its viewing range is basically the same as the actual shooting range. , which is very helpful for intuitive framing and composition.
Main features:
A great feature of SLR digital cameras is that they can exchange lenses of different specifications. This is a natural advantage of SLR cameras and is incomparable with ordinary digital cameras.
In addition, SLR digital cameras are now positioned as high-end products among digital cameras. Therefore, in terms of the area of ??the photosensitive element (CCD or CMOS) that is related to the photography quality of digital cameras, the area of ??SLR digital cameras is much larger than that of ordinary cameras. Digital cameras, this makes the photosensitive area of ??each pixel of a SLR digital camera much larger than that of an ordinary digital camera, so each pixel can show a more detailed brightness and color range, making the photography quality of a SLR digital camera obvious. Higher than ordinary digital cameras.