First, the principle of digital cameras Digital photography is a kind of filmless image recording technology, in appearance and the ordinary camera is not much different, but it is not on the film imaging, but the image after scanning the camera lens in the CCD Imaging on the sensor.
The standard methods for scanning images are point-by-point scanning (single sensor), progressive scanning (many sensors are arranged in a row), and area scanning (block sensors, sensing device matrix). Digital cameras do not use point-by-point scans; progressive scans are very similar to scanner scanners. Cameras that use this type of scan are often viewed as scanners with built-in lenses.
When shooting a color image, three filters are used to split the light into three side-by-side color channels (RGB) while capturing the tricolor information at each sensor location. When acquiring the information of the area image, the CCD queue moves according to a certain step size. If the step size is selected, the distance between the CCD queue and the queue in the three color channels is selected, and then each row of the image is The color information needs to be fully acquired after three steps of movement. Since the line scan camera uses a sequential image scan, constant lighting conditions are required. In addition, the subject to be photographed cannot move while being photographed (scanned).
Unlike the displacement of the queue sensor during scanning, the block sensor remains stationary at all times. Block sensor capture parameters are different, such as 3060 × 2036 = 6230160 pixels, the size of each pixel is 9μm × μm, the available range of this sensor is 27.5mm × 18.3mm.
There are three ways to separate colors using a block sensor, see Figure 3.2.21-22-23. Both the three sensors can be used for color separation, or a sensor can be used for color separation.
In the case of using three sensors, the separation process is achieved by prisms and color filters. You can shoot moving images at this time.
In the case of using one sensor, there are two color separation methods. One method is to use a plurality of color filters, such as a color filter wheel, to sequentially scan the image; another method is to perform a scan by using a mosaic filter, which is composed of R, G on a block sensor. , B filter elements composed of. Some of such color filters are designed in the form of a film, and some are designed in the form of a single element corresponding to a pixel. During scanning, the block sensor moves in millimeter steps. In this way, more pixels can be recorded, and the measurement resolution can be increased by 50 times. Cameras using this principle can also shoot moving images.
Second, the performance of digital cameras 1. The resolution of digital cameras hopes to continuously improve the resolution of digital cameras. People are always pursuing it. With human eye resolution (the ability of the human eye to distinguish two adjacent thin lines at a certain distance), the resolution of a digital camera is a measure of the ability to record the details of a scene. The resolution of a digital camera depends on the number of CCD components in the camera. The more components there are, the more pixels there are and the higher the corresponding resolution.
The level of the digital pixels in succession is closely related to the size of the photo that can be printed in a certain resolution. If the resolution of the printer is Ndpi, and the horizontal pixel of the image file captured by the digital camera is M, the maximum printable length of the printer is (M÷N) inches. For example, when printing with a printer with a resolution of 300 dpi, the horizontal pixels of the image file captured by the digital camera are 3,600, and the maximum length of the picture that can be printed is 12 inches. Obviously, under the premise of a certain print resolution, the larger the size of the photo to be printed, the higher the resolution of the digital camera.
2. Color depth Color depth is used to indicate the ability of a digital camera to distinguish colors. When capturing images, to obtain a nice gradient, at least 256 gray steps are required, which is represented by 8-bit binary numbers; for RGB images, 24 bits (3 bytes) are required. Digital cameras can also obtain a very wide range of gradation. Undoubtedly, the deeper the color, the more detailed the level of the image, but not the larger the bit depth, the better, on the one hand, will increase the burden on computers and storage devices. On the other hand, there is not much improvement in the tone level.
3. Focal Length The focal length of a conventional camera is set according to the film size. For example, a 35mm camera has a film size of 24mm x 36mm. At this time, 50mm can be regarded as the standard focal length. Calculated mathematically, that is, the length of the film's diagonal multiplied by a factor of 1.2. The diagonal length of many low-end digital camera sensor chips is less than 10mm, so their standard focal length is 12mm, while other high-end digital cameras may have a focal length of more than 70mm. For people's photos, the focal length of 15mm is sufficient. With such a short focal length, it is difficult to obtain a wide-angle lens because the focal length of the wide-angle lens is much shorter than the standard focal length. This is almost impossible. .
4. Aspect ratio Most people may use the traditional 35mm camera with an aspect ratio of 2:3. For digital cameras, especially some general-purpose cameras, the aspect ratio of television is usually 3:4. As for some high-resolution digital cameras (more than megapixels), there is no standard aspect ratio at all. Some manufacturers use light-sensitive chips with an aspect ratio of 1:1, and some use a 2:3 size, and of course there are devices using a 3:4 ratio.
5. The most obvious advantage of connecting a digital camera to a computer is that it can directly digitize image scenes. Digitized files can be sent directly to a computer, or they can be stored temporarily in a data storage medium that is compatible with the camera. The PCMCIA card (Personal Computer Memory Card International Association) has designed a set of good data storage methods for digital cameras. Its appearance is somewhat like a credit card and has a standard interface for transferring information to computers. If you directly transfer the captured image to your computer, you can use a standard interface such as a SCSI port or a plug-in card.
Third, digital photography and color management and scanners or other input and output devices, digital cameras can also use the color profile (Profile) to indicate its characteristics. The difference is that in scanner applications, the type and density of light are fixed values, and in digital camera applications, these values ​​are variables. Therefore, for digital photography, different profiles are created according to different types of imaging conditions. When a standard parameter is set for a studio, it cannot be applied to outdoor photography unless a set of parameter files suitable for outdoor shooting is re-created.
The standard methods for scanning images are point-by-point scanning (single sensor), progressive scanning (many sensors are arranged in a row), and area scanning (block sensors, sensing device matrix). Digital cameras do not use point-by-point scans; progressive scans are very similar to scanner scanners. Cameras that use this type of scan are often viewed as scanners with built-in lenses.
When shooting a color image, three filters are used to split the light into three side-by-side color channels (RGB) while capturing the tricolor information at each sensor location. When acquiring the information of the area image, the CCD queue moves according to a certain step size. If the step size is selected, the distance between the CCD queue and the queue in the three color channels is selected, and then each row of the image is The color information needs to be fully acquired after three steps of movement. Since the line scan camera uses a sequential image scan, constant lighting conditions are required. In addition, the subject to be photographed cannot move while being photographed (scanned).
Unlike the displacement of the queue sensor during scanning, the block sensor remains stationary at all times. Block sensor capture parameters are different, such as 3060 × 2036 = 6230160 pixels, the size of each pixel is 9μm × μm, the available range of this sensor is 27.5mm × 18.3mm.
There are three ways to separate colors using a block sensor, see Figure 3.2.21-22-23. Both the three sensors can be used for color separation, or a sensor can be used for color separation.
In the case of using three sensors, the separation process is achieved by prisms and color filters. You can shoot moving images at this time.
In the case of using one sensor, there are two color separation methods. One method is to use a plurality of color filters, such as a color filter wheel, to sequentially scan the image; another method is to perform a scan by using a mosaic filter, which is composed of R, G on a block sensor. , B filter elements composed of. Some of such color filters are designed in the form of a film, and some are designed in the form of a single element corresponding to a pixel. During scanning, the block sensor moves in millimeter steps. In this way, more pixels can be recorded, and the measurement resolution can be increased by 50 times. Cameras using this principle can also shoot moving images.
Second, the performance of digital cameras 1. The resolution of digital cameras hopes to continuously improve the resolution of digital cameras. People are always pursuing it. With human eye resolution (the ability of the human eye to distinguish two adjacent thin lines at a certain distance), the resolution of a digital camera is a measure of the ability to record the details of a scene. The resolution of a digital camera depends on the number of CCD components in the camera. The more components there are, the more pixels there are and the higher the corresponding resolution.
The level of the digital pixels in succession is closely related to the size of the photo that can be printed in a certain resolution. If the resolution of the printer is Ndpi, and the horizontal pixel of the image file captured by the digital camera is M, the maximum printable length of the printer is (M÷N) inches. For example, when printing with a printer with a resolution of 300 dpi, the horizontal pixels of the image file captured by the digital camera are 3,600, and the maximum length of the picture that can be printed is 12 inches. Obviously, under the premise of a certain print resolution, the larger the size of the photo to be printed, the higher the resolution of the digital camera.
2. Color depth Color depth is used to indicate the ability of a digital camera to distinguish colors. When capturing images, to obtain a nice gradient, at least 256 gray steps are required, which is represented by 8-bit binary numbers; for RGB images, 24 bits (3 bytes) are required. Digital cameras can also obtain a very wide range of gradation. Undoubtedly, the deeper the color, the more detailed the level of the image, but not the larger the bit depth, the better, on the one hand, will increase the burden on computers and storage devices. On the other hand, there is not much improvement in the tone level.
3. Focal Length The focal length of a conventional camera is set according to the film size. For example, a 35mm camera has a film size of 24mm x 36mm. At this time, 50mm can be regarded as the standard focal length. Calculated mathematically, that is, the length of the film's diagonal multiplied by a factor of 1.2. The diagonal length of many low-end digital camera sensor chips is less than 10mm, so their standard focal length is 12mm, while other high-end digital cameras may have a focal length of more than 70mm. For people's photos, the focal length of 15mm is sufficient. With such a short focal length, it is difficult to obtain a wide-angle lens because the focal length of the wide-angle lens is much shorter than the standard focal length. This is almost impossible. .
4. Aspect ratio Most people may use the traditional 35mm camera with an aspect ratio of 2:3. For digital cameras, especially some general-purpose cameras, the aspect ratio of television is usually 3:4. As for some high-resolution digital cameras (more than megapixels), there is no standard aspect ratio at all. Some manufacturers use light-sensitive chips with an aspect ratio of 1:1, and some use a 2:3 size, and of course there are devices using a 3:4 ratio.
5. The most obvious advantage of connecting a digital camera to a computer is that it can directly digitize image scenes. Digitized files can be sent directly to a computer, or they can be stored temporarily in a data storage medium that is compatible with the camera. The PCMCIA card (Personal Computer Memory Card International Association) has designed a set of good data storage methods for digital cameras. Its appearance is somewhat like a credit card and has a standard interface for transferring information to computers. If you directly transfer the captured image to your computer, you can use a standard interface such as a SCSI port or a plug-in card.
Third, digital photography and color management and scanners or other input and output devices, digital cameras can also use the color profile (Profile) to indicate its characteristics. The difference is that in scanner applications, the type and density of light are fixed values, and in digital camera applications, these values ​​are variables. Therefore, for digital photography, different profiles are created according to different types of imaging conditions. When a standard parameter is set for a studio, it cannot be applied to outdoor photography unless a set of parameter files suitable for outdoor shooting is re-created.
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