Optical resolution refers to the degree of fineness that a scanner can actually sample an image when scanned, expressed in dpi (dots per inch) or ppi (pixels per inch).
For plane scanners, the optical resolution is divided into horizontal and vertical resolutions. The horizontal resolution mainly depends on the number of pixels of the linear CCD and the width of the scan (resolution = number of CCD pixels/maximum scan width). The vertical resolution is based on the number of rows the stepper motor in the scanner has moved the scan head over the unit of time, so the vertical resolution is related to the stepper motor and the mechanical drive section. Among the two resolution indicators of the scanner, the more important is the horizontal resolution. The general reference to optical resolution refers to horizontal resolution.
For example, for a scanner with a pixel CCD of 5000, the maximum scan width of the scanner is 8.3 in, then:
Optical resolution=5000/8.3=600dpi
For drum scanners, the optical resolution mainly depends on the width of the number of scan lines, that is, the distance the drum rotates in one revolution of the scan head. The finer the scan line, the higher the resolution; on the contrary, the lower the resolution.
The higher the optical resolution, the greater the amount of image information that can be acquired, and the more detail that is contained in the scanned output image. The size of the optical resolution of the scanner is related to the maximum magnification of the image formed by scanning with this scanner and the maximum number of screens during printing. The relationship among the scanning resolution, the image magnification and the number of printing screens is:
Scan Resolution = Magnification × Screen Number × Quality Factor (1.5 to 2)
It can be seen that when the printing screen number is fixed, the scanning resolution of the scanner limits the magnification of the image. When the maximum magnification of the image is limited by the scanning resolution, only the reduction of the magnification limit can only reduce the magnification or the number of printing screen lines.
â— Maximum Resolution Based on the optical resolution, the pixel resolution of the scanned image can be increased if the pixel is inserted by the software. The maximum resolution is the resolution obtained by inserting the pixels to the maximum extent. Therefore, it is also called the interpolation resolution. This refers to the resolution that can be achieved by calculation. The maximum resolution is different from the optical resolution. Although the maximum resolution can improve the resolution of the scanned image, it cannot actually increase the amount of information in the image, but it will make the image appear blurred. Software interpolation increases the resolution and the image quality deteriorates. However, with this method, high-magnification images can be scanned from the software. The maximum resolution is usually 2 to 4 times the optical resolution.
Understand the meaning of the above two resolutions, we can correctly determine the quality of a scanner when purchasing the scanner.
â— Maximum Density Range The largest density range, also known as the maximum density dynamic range, is the density range that the scanner can recognize when the original layer changes. The small maximum density range will cause the detail level of the original dark tone to be lost. Even though the image in this area still changes in depth, the light-sensing device cannot recognize the signal, and the output signal is the same. Therefore, the scanned image has no hierarchy in the area. The same hue of change. Only scanners with a high density range can reflect the details of these darker parts. Darkness is therefore the key to verifying scanner performance.
In general, the density of reflected originals is less than 2.0D, and the maximum density of transmitted originals can reach 3.5D. Therefore, the requirements for scanning a transmitted original are much higher for scanners.
â— Color Bit depth Color bit depth is the number of layers the scanner can recognize for each color. The early scanner had only one digit, and only two gray scales could be recorded, namely black and white. At present, there are four color digits for scanners: 8-bit, 10-bit, 12-bit, and 16-bit, which are commonly referred to as 24-bit, 30-bit, 36-bit, and 48-bit scanners. Theoretically, the 24-bit scanner can distinguish between 256 shades of gray and 16.77 million colors; the 30-bit scanner can distinguish between 1024 shades of gray and 1 billion colors; and the 36-bit scanner can distinguish between 4096 shades of gray and 68.7 billion colors The 48-bit scanner can distinguish between 65536 shades of gray and 281 trillion colors. Therefore, the higher the color bit number of the scanner, the richer the captured color, the more layers of the scanned image, and the greater the dynamic range.
â— Magnification Magnification is the magnification at which the scanner reduces or enlarges the original. Scaling is a processing program that generates a larger or smaller image in the scanning software. When the scanning image scaled by the scanning software is sent to the image editing program, there is no need to change the size of the image again. In the scanning software, the zoom ratio is inversely proportional to the optical resolution, and the larger the zoom ratio of the image, the lower the optical resolution. When using the maximum resolution, the zoom ratio can only be less than 1.
â— Scanning Originals The scanner scans originals mainly referring to manuscripts, texts, graphics, etc. Even three-dimensional objects such as coins, watches, or textiles are commonly referred to as scanning originals.
When it comes to scanning a manuscript, it is often described as an original manuscript. The original index refers to the scanner's ability to adapt to the original. It can be expressed by the original type, original size, and original density range.
The original type refers to transmissive originals, reflective originals, color negatives, color positives, colored originals, black and white originals, and lined originals.
The maximum size of the scanned original refers to the maximum size of the original scanned by the scanner. This indicator is important for reflecting originals. Because of the large size of the reflec- tor, the barrel of the drum scanner and the flatbed scanner have certain limitations. In order to adapt to different sizes of originals, manufacturers have also introduced scanners of different sizes, commonly used A4 format, A3 format scanners and A0 format, A1 format engineering drawings scanner.
◠Scanner Speed ​​The scanner speed is closely related to system configuration, scan resolution settings, scan size, and magnification. Under normal circumstances, scanning black and white, grayscale images, scanning speed of 2 ~ 100ms / line; scanning color images, scanning speed of 5 ~ 200ms / line. In general, people always want the scanner to be fast, but the scanner works by scanning the light source of the scanner, using a color separation method and a CCD (charge coupled device) or PMT (photomultiplier tube) to collect the scanned image. The light information of the object, and transmits the light information to a computer image file. The speed of the scanner is good, but it does not affect the image quality. Therefore, it is not the scanner that scans as fast as possible. Scanners with very high scanning speeds may lose some image information during the scanning process. Some scanners scan fast at low resolutions, but scanning speeds at high resolutions are not necessarily fast. Therefore, the speed of the scanner must be improved under the premise of ensuring quality.
For plane scanners, the optical resolution is divided into horizontal and vertical resolutions. The horizontal resolution mainly depends on the number of pixels of the linear CCD and the width of the scan (resolution = number of CCD pixels/maximum scan width). The vertical resolution is based on the number of rows the stepper motor in the scanner has moved the scan head over the unit of time, so the vertical resolution is related to the stepper motor and the mechanical drive section. Among the two resolution indicators of the scanner, the more important is the horizontal resolution. The general reference to optical resolution refers to horizontal resolution.
For example, for a scanner with a pixel CCD of 5000, the maximum scan width of the scanner is 8.3 in, then:
Optical resolution=5000/8.3=600dpi
For drum scanners, the optical resolution mainly depends on the width of the number of scan lines, that is, the distance the drum rotates in one revolution of the scan head. The finer the scan line, the higher the resolution; on the contrary, the lower the resolution.
The higher the optical resolution, the greater the amount of image information that can be acquired, and the more detail that is contained in the scanned output image. The size of the optical resolution of the scanner is related to the maximum magnification of the image formed by scanning with this scanner and the maximum number of screens during printing. The relationship among the scanning resolution, the image magnification and the number of printing screens is:
Scan Resolution = Magnification × Screen Number × Quality Factor (1.5 to 2)
It can be seen that when the printing screen number is fixed, the scanning resolution of the scanner limits the magnification of the image. When the maximum magnification of the image is limited by the scanning resolution, only the reduction of the magnification limit can only reduce the magnification or the number of printing screen lines.
â— Maximum Resolution Based on the optical resolution, the pixel resolution of the scanned image can be increased if the pixel is inserted by the software. The maximum resolution is the resolution obtained by inserting the pixels to the maximum extent. Therefore, it is also called the interpolation resolution. This refers to the resolution that can be achieved by calculation. The maximum resolution is different from the optical resolution. Although the maximum resolution can improve the resolution of the scanned image, it cannot actually increase the amount of information in the image, but it will make the image appear blurred. Software interpolation increases the resolution and the image quality deteriorates. However, with this method, high-magnification images can be scanned from the software. The maximum resolution is usually 2 to 4 times the optical resolution.
Understand the meaning of the above two resolutions, we can correctly determine the quality of a scanner when purchasing the scanner.
â— Maximum Density Range The largest density range, also known as the maximum density dynamic range, is the density range that the scanner can recognize when the original layer changes. The small maximum density range will cause the detail level of the original dark tone to be lost. Even though the image in this area still changes in depth, the light-sensing device cannot recognize the signal, and the output signal is the same. Therefore, the scanned image has no hierarchy in the area. The same hue of change. Only scanners with a high density range can reflect the details of these darker parts. Darkness is therefore the key to verifying scanner performance.
In general, the density of reflected originals is less than 2.0D, and the maximum density of transmitted originals can reach 3.5D. Therefore, the requirements for scanning a transmitted original are much higher for scanners.
â— Color Bit depth Color bit depth is the number of layers the scanner can recognize for each color. The early scanner had only one digit, and only two gray scales could be recorded, namely black and white. At present, there are four color digits for scanners: 8-bit, 10-bit, 12-bit, and 16-bit, which are commonly referred to as 24-bit, 30-bit, 36-bit, and 48-bit scanners. Theoretically, the 24-bit scanner can distinguish between 256 shades of gray and 16.77 million colors; the 30-bit scanner can distinguish between 1024 shades of gray and 1 billion colors; and the 36-bit scanner can distinguish between 4096 shades of gray and 68.7 billion colors The 48-bit scanner can distinguish between 65536 shades of gray and 281 trillion colors. Therefore, the higher the color bit number of the scanner, the richer the captured color, the more layers of the scanned image, and the greater the dynamic range.
â— Magnification Magnification is the magnification at which the scanner reduces or enlarges the original. Scaling is a processing program that generates a larger or smaller image in the scanning software. When the scanning image scaled by the scanning software is sent to the image editing program, there is no need to change the size of the image again. In the scanning software, the zoom ratio is inversely proportional to the optical resolution, and the larger the zoom ratio of the image, the lower the optical resolution. When using the maximum resolution, the zoom ratio can only be less than 1.
â— Scanning Originals The scanner scans originals mainly referring to manuscripts, texts, graphics, etc. Even three-dimensional objects such as coins, watches, or textiles are commonly referred to as scanning originals.
When it comes to scanning a manuscript, it is often described as an original manuscript. The original index refers to the scanner's ability to adapt to the original. It can be expressed by the original type, original size, and original density range.
The original type refers to transmissive originals, reflective originals, color negatives, color positives, colored originals, black and white originals, and lined originals.
The maximum size of the scanned original refers to the maximum size of the original scanned by the scanner. This indicator is important for reflecting originals. Because of the large size of the reflec- tor, the barrel of the drum scanner and the flatbed scanner have certain limitations. In order to adapt to different sizes of originals, manufacturers have also introduced scanners of different sizes, commonly used A4 format, A3 format scanners and A0 format, A1 format engineering drawings scanner.
◠Scanner Speed ​​The scanner speed is closely related to system configuration, scan resolution settings, scan size, and magnification. Under normal circumstances, scanning black and white, grayscale images, scanning speed of 2 ~ 100ms / line; scanning color images, scanning speed of 5 ~ 200ms / line. In general, people always want the scanner to be fast, but the scanner works by scanning the light source of the scanner, using a color separation method and a CCD (charge coupled device) or PMT (photomultiplier tube) to collect the scanned image. The light information of the object, and transmits the light information to a computer image file. The speed of the scanner is good, but it does not affect the image quality. Therefore, it is not the scanner that scans as fast as possible. Scanners with very high scanning speeds may lose some image information during the scanning process. Some scanners scan fast at low resolutions, but scanning speeds at high resolutions are not necessarily fast. Therefore, the speed of the scanner must be improved under the premise of ensuring quality.
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