Among the various scanner models presented in stores, tablet devices can be distinguished. This is a popular budget option that has all the necessary functions for digitizing documentation. We will talk about the main parameters of such scanners in our article.
Key Features of Flatbed Scanners
The device got its name thanks to a glass plate - a tablet, on which the original photo (or document) is placed with the scanned surface down.
The main advantages of its use are compactness, ease of use and versatility. Document processing occurs without additional influences (bending, deformation, etc.). Devices do not require maintenance and are designed for a long service life.
Power can be supplied from the battery, via a USB port on a PC or via Wi-Fi.
The device performs two main functions:
- Digitization of text documents;
- Scan photos and various images.
REFERENCE! Processing of both color, and black-and-white originals is provided.
The operation scheme is simple: inside the device there is a scanning head, which, when a command is issued (manually or in automatic mode), moves together with the light source by means of a stepper motor. Light rays are reflected from the processed document, captured by a system of mirrors, then photosensitive sensors pass and converted into electrical signals. As a result, a digital copy of the image is formed from the signals.
Resolution
This is the main characteristic of the scanner, on which the quality and detail of the resulting images depend.
The passport indicates two values that mean horizontal and vertical resolution, respectively. The horizontal value is taken as the basis, since during image processing the mechanism moves from top to bottom. It is called optical resolution.
In accordance with this indicator, tablet models are divided into classes:
- Standard. Suitable for business workflows and the usual needs of users, the parameter varies from 300 to 600 dpi.
- Average. Used in publishing, resolution can reach 1800 dpi.
- High quality, up to 2000 dpi and higher. In its parameters, it is not inferior to professional devices.
IMPORTANT! For scanning documents, the standard value is sufficient, if the digitized photo will be further processed by graphic editors, then we recommend choosing the middle class.
Performance
This value means the speed of scanning documents. It depends on the selected resolution and document size - the higher they are, the lower the parameter in question.
For example, in one pass of the scanning head, a low-quality image (less than 300 dpi) is processed, which ensures high performance to the detriment of other indicators.
The standard values for budget devices are from 4 to 5 pages per minute, which corresponds to approximately 600 dpi.
Bit depth or color depth
Color rendering is calculated in bits and affects the colorization and number of shades of the document. The parameter is determined by the capabilities of photosensitive sensors (CCD or CIS) and ADC (processor that converts an analog signal to digital).
Models are available with a depth of 24 to 48 bits. You can find 96-bit models, but they are already professional type and are much more expensive.
The color depth, which shows how many colors the scanner on the original can distinguish, is called internal. Its optimal value, contributing to high-quality scanning -36 bits.
The color representation that is transferred from the device to the computer is external. To get the best result comparable to the source, at least 36 bits are selected.
REFERENCE! These sensors differ in the type of light sources used: fluorescent (CCD) or LED (CIS), the latter last much longer.
Dynamic range
This parameter characterizes the difference between the lightest and darkest areas of the image. Simply put, it shows the ability of the scanner to recognize how dark the source is. The so-called optical density increases with the growth of dark shades.
For example, a density of 0.01 means white shades, up to 4 and above - this is black indistinguishable to the eyes.
White light is perfectly recognized by scanners, at the same time only sensors with high sensitivity are able to "see" dark areas.
The higher the dynamic range value, the better the final scan result.
REFERENCE! In cheap models, this parameter is usually not specified. But you can roughly determine the numbers: scanners 24 bits perceive from 2.4 to 2.6; 30 bits - from 2.6 to 3; 36 bits - from 3.
Type of connection to PC
Modern devices use a USB connection to a computer. The USB connection can be version 1.1 or 2.0. Structurally, these are the same type of connectors, differing in data transfer speed: 12 Mbit / s, in comparison with 480 Mbit / s. They are fully compatible and interchangeable.
Another connection option is parallel ports (SCSI or PCMCIA standards), they are connected to the rear panel of the PC, where there are corresponding connectors.
Scanned Document Format
Typically, the scanner driver supports recording received files in such common formats as Jpeg, PDF, etc.
In some cases, to save scanned texts, it may be necessary to install a recognition program on the PC, if by default it is assigned one of the extensions intended for photos (Jpeg, tiff, etc.).
You can change the file format, for example, in the ABBYY FineReader application, it has an extensive set of tools for recognizing text blocks, correcting and changing them, and then saves the result in the required file type. A wide range of extensions is available.
REFERENCE! The standard size of the originals used is A4, but some models support A3, A5, etc.
Supported Operating Systems
As a rule, a device with a licensed program (driver) is provided in the device’s kit, which provides an optimal operating mode. If there is no such diskette, then you need to go to the scanner manufacturer's website and download the necessary utility.
According to user reviews, software is difficult to learn for individual models, in these cases, downloading and installing the program from the Internet can be an alternative.
Manufacturers produce devices that are compatible with all popular Windows and MAC systems. There are no special requirements for the characteristics of these operating systems.
IMPORTANT! In particular cases, incompatibility occurs, for example, Windows Vista may "conflict" with the new driver. The issue is solved by finding the right program, as an extreme option, you will have to install another OS.
Additional features of flatbed scanners
Auxiliary functions are implemented using elements such as film modules and automatic feeding of originals.
Some devices have a special adapter that allows you to scan film, both negative and positive, and slides.
With this tool, the so-called film scanner is replaced - a special apparatus for digitizing films. The cost of specialized models can significantly hit the pocket, so the presence of an additional function in a flatbed scanner can save the owner money.
Automatic feeding of originals allows you to load immediately a stack of documents into the tray, which will move as you scan. This allows you to reduce the number of user actions, which is especially important with a large amount of work.
What options to consider when choosing a scanner for home
Before buying, decide on the purpose of why you are purchasing the device, how often you will use it, and what level of quality will satisfy you.
When choosing a device, additionally evaluate its following indicators:
- convenient connection to a PC;
- hardware compatibility;
- options;
- available sizes of documents (A4 and others).
High requirements for the quality of the material at the exit, the need to process originals of different sizes and the availability of auxiliary tools will make your purchase much more expensive.
Otherwise, a standard tablet at an affordable price is the best option.
We hope that our article helped to figure out what characteristics to pay special attention to when choosing a flatbed scanner.
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