Max. resolution
The highest resolution of the digital image generated by the scanner during operation. Specified in dots per inch — dpi (dots per inch).
The higher the scan resolution, the higher the resolution of the resulting image will be (with the same size of the source material) and the more accurately small details will be transmitted on it. On the other hand, high resolution noticeably affects the price of the scanner, increases the processing time and the size of the resulting file — despite the fact that the real need for high detail is not always present, and in some cases it is even unnecessary (for example, when processing an image with small artifacts, not visible at low detail). Therefore, when choosing by this parameter, you should not chase high resolution values — you should proceed from the real need and the specifics of the intended use of the scanner.
The simplest modern scanners have a resolution of about 300x300 dpi — this is quite enough for text recognition with an average font size. And in high-end professional models, this figure can exceed 7000x7000 dpi.
Max. scan area
The maximum image size that the scanner can process at one time, both horizontally and vertically. You should pay attention to this parameter if you need the exact dimensions of the scanner's working area, down to a millimetre: although standard formats are used to designate these dimensions (see "Format"), in fact the dimensions may differ from them.
Colour depth (int.)
Under the internal colour depth is meant the number of shades of the image that the scanner itself can recognize; it should not be confused with external depth, which is the amount of hue transmitted to the computer (see below). Colour depth is expressed as the number of bits of information used to encode data about each colour. The total number of colour shades in this case is 2 to the power of n, where n is the colour depth. So, a 24-bit scanner recognizes 16.7 million colours — which is more than one and a half times more than the human eye, and quite enough for simple everyday tasks. In more advanced professional models, colour depth can reach 96 bits. Although the characteristics of the image transmitted to the computer are described by the external colour depth (which can be less than the internal colour depth), the internal depth, however, also affects its quality: other things being equal, a scanner with a higher internal depth provides more accurate colour reproduction.
Mono scanning
The black and white scanning speed provided by the device. Usually, the maximum processing speed for an A4 sheet is indicated, i.e. speed at the lowest resolution. In fact, the speed is usually lower and depends on both the resolution and the size of the original material. The higher the scanning speed, the more convenient it is to work with the scanner; pay special attention to this parameter if you plan to work with numerous black and white images.
Colour scanning
Colour scanning speed provided by the device. In fact, it depends on the selected resolution, colour depth and original dimensions; the characteristics most often indicate the speed for an A4 sheet at the minimum resolution and colour depth, i.e. maximum possible speed. If you only need to scan one or more sheets from time to time, high speed is not too critical, but for working with a large amount of materials, you should look for fast models.
Document autofeed
The maximum number of sheets of standard weight (80 g/m²) paper that can be placed in the scanner's auto feed system at a time. These systems are similar to those installed in printers: a stack of sheets is installed in a special tray, and each of them is fed in turn for scanning. It is worth paying attention to models with this function if you often have to work with numerous documents: you will not need to monitor the process and manually feed sheets — just load the originals into the automatic document feeder and press the button. Many document feeders, some flatbeds, and almost all combination scanners have an ADF (see "Type"). It works, however, only with separate sheets and cannot cope with larger media.
Data transfer
— Wi-Fi. A wireless interface primarily used to build local computer networks. In many respects it is similar to the LAN described below (in particular, it allows using the scanner as a network device), but it compares favorably due to the absence of a cable and the ability to work directly through walls. In addition, relatively recently, Wi-Fi modules have appeared with the ability to directly connect between devices — for example, to control a scanner from a tablet and transfer processed materials to the tablet directly, without creating a computer network. However
scanners with Wi-Fi are quite expensive.
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USB. Universal interface for connecting various peripherals to a computer, including scanners. Today, it is the most common port of this type; at least one USB input is provided by the vast majority of PCs and laptops.
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SCSI. Universal interface for connecting computer peripherals; has a good speed, however, it is much less common than its analogues, besides it is considered obsolete and is gradually being replaced by other standards.
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IEEE-1394. Universal port, in many ways similar to USB (see above). Provides higher speed than the most common USB 2.0, but is much less common.
-LAN. Connector for connecting various devices to a local computer network. A scanne
...r with this interface can be connected as a network device and used with it by any computer on the network, which can be especially useful in offices.Power source
— From the network. The most common option is to connect to a conventional 230 V power supply. This power supply provides enough power to operate any, even the fastest and most performant scanners. Its disadvantage is, in fact, the need for an electrical network.
— From USB.
Powered via USB port — the same through which it connects to the computer. This significantly increases the battery life of the scanner — in particular, it can be used with a laptop in places where there is no access to a 230 V network, which is especially important for portable models (see "Portable Design"). On the other hand, the performance of such devices is usually low, and the power of the USB port is not always enough for power supply (which is especially true when using USB hubs).
— Autonomous. Power supply of the scanner from its own batteries (accumulator or replaceable batteries). Such models are as autonomous as possible, because do not require a power cord to operate, and many of them are able to act as separate devices without being connected to a PC at all. Their disadvantage is the risk of switching off at the most inopportune moment due to the exhaustion of the charge — then you have to either change the batteries (which at least requires fresh ones) or recharge the battery (which takes time).
Noise level
The maximum noise level produced by the scanner during operation. Theoretically, the lower this parameter, the more comfortable the use of the device, however, the vast majority of scanners have a noise level much lower than the general sound background in a small office (this background is 40-50 dB). Therefore, it is worth paying special attention to the noise level if you plan to use the device at home at a later time, or in other environments where even a slight noise may be undesirable.