How can I prevent being ripped off when buying a scanner? Understanding some of the scanner's purchase knowledge and points is the best and most important means. As we all know, the scanning effect of the scanner depends on the scanner speed, scanning accuracy, color, etc. As long as you understand these indicators clearly when you purchase and try them in person, generally speaking, the quality of a scanner will definitely be displayed immediately.
First of all, for the average user, how much resolution is enough for the scanner? As you know, the resolution of a scanner is usually expressed in points per inch of length, or DPI. Scanners on the market have optical resolutions of 300×600DPI, 600×1200DPI, and 1200×1200. Although the optical resolution of 300×600DPI is enough for ordinary users and 300DPI and 600DPI are enough for scanning ordinary documents and photos, 1200DPI should be your first choice if the price is similar. In addition to the optical resolution, a maximum resolution is usually marked on the box of the scanner. The optical resolution of 600×1200DPI is 9600DPI. In fact, the interpolation resolution is obtained by inserting the calculated extra pixels between the real pixels through the software. Interpolation resolution is not good for improving image accuracy. In fact, as long as the software supports it and your machine is strong enough, this resolution can be infinite. Everyone must make sure when buying, so as to avoid dealers using these values to deceive you.
Secondly, an important indicator for the scanner is the color depth value. Everyone can also do some understanding when buying a scanner, especially the high speed scanner, because the higher color depth digits can ensure that the image color reflected by the scanner is as consistent as possible with the real color of the object, and the image color will be more abundant. The color depth value of the scanner is generally 24BIT, 30BIT, 32BIT, 36BIT. The color depth value of the general optical resolution of 600 × 1200DPI is 36BIT, and the high one is 48BIT. The gray value refers to the number of levels to divide the entire color area of the image from pure black to pure white during gray scale scanning. When editing images, 8BIT is generally used, that is, 256 levels. The mainstream scanner is usually 10BIT, up to 12BIT. But for general users, a 24-bit scanner is enough. If you are dealing with slides or negatives, you must have at least 30 bits. It should be said that most of the cheap flatbed scanners have a minimum of 30 bits of color and are enough to handle any document and image. So you may ignore the scanners with only 24bit color in the future. But you still need to know this when choosing a scanner, especially for second-hand scanners.
Furthermore, for the interface of the scanner, a scanner with a USB interface should be your first choice. It has the characteristics of fast transmission speed and more convenient use of hot-plug. The SCSI interface is still a little troublesome for general users, and the EPP parallel port scanner can be connected to the computer by using ordinary parallel lines.
In addition, what kind of photosensitive element the scanner uses has a great influence on the performance of the scanner. At present, there are three main types of photosensitive devices used in scanners: photomultiplier tubes, charge-coupled devices (CCD) and contact photosensitive devices (CIS or LIDE). The photomultiplier tube is actually an electronic tube, which is generally only used on expensive professional roller scanners. At present, CCD has become the most widely used photosensitive element. Although CIS technology appeared at the same time as CCD technology, it could only be used for low-end handheld black and white scanners in the early days due to technical limitations. CIS technology has only achieved a major breakthrough since 1999, and its limit resolution has been increased from 200dpi to 600dpi. Its biggest advantage is that the production cost is low, only about 1/3 of that of the CCD, so it is widely used in many low-end scanners. However, considering only performance, CIS has obvious birth defects. Since the lens cannot be used, it can only be scanned close to the manuscript, and there is still a certain gap between the actual clarity and the nominal index. And because there is no depth of field, it is impossible to scan three-dimensional objects. Therefore, the development prospects of CIS are very bleak. Manufacturers still value CCD technology, and will optimize and improve details such as the lens group design of the product to further reduce the thickness of the scanner.
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