How does the scan work? What is a scanner for and how to use it

If you use a separate print device, you will not be able to scan documents from the printer to your computer. To create a photocopy of a page, you need a scanner. It is performed as a separate module or in the same housing with the printer. Equipment that combines the functions of a printer and scanner is called an MFP (multifunction device).

Connecting the MFP to a computer

Modern printing and scanning equipment is connected via a USB interface. To connect the scanner, insert one cable plug into the connector on the case, and the second into any USB port on the PC. Plug and Play technology allows you to connect new equipment without having to restart Windows. However, some scanners perform a connection check during initialization, so it is recommended that you press the power button only after connecting to the PC.

Pay attention! Network MFPs connect to a computer through a router. The connection is made using an Ethernet cable or via WiFi. For correct operation, make sure that access point isolation is not enabled on your router.

Adding an MFP and installing software

Printers and scanners usually come with a disk containing instructions and drivers for Windows. Install the software from this disk or download the driver from the manufacturer's website. In addition to the driver, the CD or downloaded archive may also contain specialized utilities designed for printing, scanning and feedback from the MFP. It is also recommended to install these applications to make interacting with the scanner easier and improve the quality of work.

After installation, open the list of connected equipment in the Windows Control Panel. The new device should appear at the top of the page. In the context menu, check the “Set as default” checkbox. To check operation, print a test page or do a test scan. To edit the settings, select Properties.

Important! If your scanner is not in this list, check the “Other Devices” section of Windows Manager. You can update the driver through the MFP context menu in this section.

How to scan documents from a printer to a computer

You can start the scanning process in several different ways:

Use the manufacturer's software to scan documents from the printer to your computer.
Open the “Control Panel -> Devices” window, find the MFP and right-click on it. In the context menu, select “Start Scan”, specify the parameters in the Windows dialog box.
Launch the standard graphics editor Paint. In the main menu, open the “File” section and select the “From a scanner or camera” line.

And publish version 2.0, improved and expanded. Thanks to everyone who helped make this post better! (We will not delete the previous post for those who have already added it to their favorites, but we will add a link to the new version)

Our technical support service is often asked for help in choosing a scanner. You can find a variety of types of scanners on the market: image scanner, barcode scanner, film scanner, biometric retinal or fingerprint scanner, etc... We decided to shed light on this issue and in the first post on this topic we will briefly explain how they differ in general document scanners, which, in particular, Epson offers for home and office, and what technologies are used in them.

Printer with scanner or separate scanner?

You can convert a document into electronic form using a scanner installed in an MFP (multifunction printer with a built-in scanner and copier) or a separate device - flatbed or streaming.

If you have a limited budget, it is more convenient to consider the option of purchasing an MFP. The scanners in such devices are slightly inferior to individual scanners in terms of scanning speed and quality of the resulting image.

If you plan to transfer large volumes of documents to the archive (for example, in an office or accounting department) or the high quality of scanned materials is extremely important to you (for converting analog photos and films into electronic format), we recommend that you pay attention to a separate scanning device. Let's look at why this is so.

Scanning technologies

The differences between scanners are largely due to the features of the scanning technologies that they use. Epson devices use 2 technologies – CCD and CIS.

CCD– data reading technology based on CCD (charge-coupled device) sensors. During the scanning process, light from the source hits the image, after which it is reflected (refracted) and, using an optical system of mirrors, is directed to a line of light-sensitive elements (CCD sensors), and then transformed into a digital signal using an analog-to-digital converter (ADC). The CCD sensor guarantees good depth of field and excellent color reproduction, which is why most professional scanners are manufactured using CCD technology.

CIS– technology using contact image sensors (CIS). This technology is often used in inexpensive scanners. Instead of the complex optical system of CCD scanners, it uses multiple rows of red, green and blue light-emitting diodes (LEDs) that sequentially illuminate the scanned image. The reflected light hits contact image sensors located across the entire width of the scanning area, very close to the surface of the glass tablet or document. Then, using an ADC, the signal from the sensors is converted into a digital code.

In short, Sklifosovsky!

Scanners based on CCD technology allow you to obtain images higher quality and resolution, and also allow you to scan “bas-reliefs” due to the absence of the need to focus the scanning beam (see “Scanography”). Scanners based on CIS technology do not have this advantage, however, as a rule, they still more compact and cheaper to manufacture, therefore they have found application in universal or low-cost devices.

Case study

For clarity, here are two examples of images obtained from scanners based on different technologies. The subject to be scanned is a medium-thick book.

If, when scanning a spread, you moderately (without “fanaticism”) press the book closer to the glass with the scanner lid, then the difference is noticeable. Due to the absence of the need to focus the scanning beam, a scanner using CCD technology produces excellent results.

Even with strong pressure, a CIS scanner finds it difficult to produce a completely focused image. At the same time, both the book and the scanner lid got damaged during scanning, because quite a lot of force has to be applied to press it.

To summarize, we can say that both types of scanners are quite suitable for scanning flat documents. But for scanning photographs, films and book spreads, it is better to choose a scanner with a CCD matrix due to its greater depth of field and more accurate color rendition.

Scanner resolution

The resolution or resolving power of a scanner is the number of dots that the light sensors can read from each horizontal stripe of the image (the image is read line by line). Resolution is measured in dots per inch (dpi – Dots per Inch) (see *).

Actually, the higher the scanner resolution, the more you can enlarge the image without losing quality, which is convenient, for example, for further processing in an editor or for printing. To simplify things, we will give analogies from the world of photography. The resolution of the scanner can be compared with the resolution of the matrix of a digital camera: the larger it is, the higher the resolution of the image can be obtained “in an honest way”, without software tricks.

There are two types of resolution: optical and interpolation. Optical resolution (“optical zoom” in a digital camera) is a hardware characteristic of the device. It depends on the number of photosensitive sensors per inch of the horizontally scanned image. Interpolation resolution is obtained by interpolating the real resolution to, usually, a higher resolution using bilinear, bicubic and other algorithms (“digital zoom” in digital). The result is an artificially increased number of pixels.

How much DPI does it take to screw in a light bulb?

Let's look at the example of the Epson Perfection V850 Pro scanner. Scanner hardware resolution – up to 6400×9600 dpi, where 6400 dpi is the horizontal scanning resolution, which is related to the density of the photosensitive elements in the scanner matrix, and 9600 dpi is the vertical scanning resolution, which depends on the accuracy of the carriage movement and processing of scanning results. You should focus on the first number, because this, in fact, is the actual (“optical”) resolution of the flatbed scanner. Interpolation resolution 12800 dpi is the resolution obtained as a result of software processing of a scanned original by enlarging it four times (two in width and two in length). It does not improve image quality, but it can help when scanning graphic sketches (the lines are smoother), as well as when enlarging small images when you don’t have a graphics editor at hand, but you need to see the scanned object better.

Now let’s remember that for high-quality photo printing in A4/A3 format, the optimal resolution printer 300-600 dpi is considered. Those. anything more is the lot of cool photographers, expensive glossy magazines, etc. Now let’s estimate what resolution the image will have, which is intended for printing in A4 format at 600 dpi:

Wow, this image turns out to be 4961x7016 = 34 megapixels.

Now let’s figure out what image, ahem, resolution we’ll get when scanning A4 in 6400 dpi:

I suddenly didn’t want to scan anything... 4000 gigapixels, probably too much for one A4 sheet!

Why then do scanners have such crazy resolutions?

It's simple - just to scan films and photos of small sizes! When scanning 35x24mm film, of course, 600 dpi is not enough. Therefore, the scanner specifications indicate the maximum supported resolution in film scanning mode. For scanning documents and medium-sized photos, 600 dpi is more than enough, as we were able to see in the example above.

Scanner type - flatbed or streaming

In order to decide on the type of scanner, we recommend paying attention to 2 parameters: the type of documents being scanned and the area that you are willing to allocate for the new “tenant”. Stream scanners are compact devices that can be easily placed on your desktop. A flatbed scanner will take up at least 2 times more space than its streaming counterpart, but there are also significantly more options for materials that it will scan.

The table shows data on Epson scanners.

Flatbed scanners

Distinctive feature flatbed scanner is a flat glass on which the scanned object is placed - a page with text or an image. The inside of the scanner lid is plain and serves as a universal background for reading the size of the document being scanned. To scan bulky objects, such as books, the cover can be removed. Tablet devices are divided into scanners for home (Perfection series) and business (WorkForce and Expression).

Home and professional photo scanners

The Epson Perfection series flatbed scanners for home allow you to scan documents, brochures and magazines, digitize and process photographs, slides and films, removing damage from them and restoring color (using the supplied software).

The youngest model in the line, the Epson Perfection V19 scanner, can be connected to a computer using a micro-USB cable; the device does not require independent power supply. The only scanner in the Epson Perfection line using CIS technology. However, it scans at 4800x resolution and provides additional options for enhancing images using Epson Easy Photo Fix software. Using the software, you can remove dust particles from a scanned image, restore color, and correct background light. If you are looking for an inexpensive, but “angry” flatbed scanner, the Epson Perfection V19 is likely to suit you perfectly.

The top model of professional photo scanners - Epson Perfection V850 Pro is based on CCD technology for professional photo processing, films and slides(35 mm, medium format and 9x12 cm format). The scanner can adjust the height of the film holder to adjust the position of the focus point, which helps achieve sharper scanning. Special holder plates press the film against the glass, which avoids the appearance of Newton's rings during scanning.

Two built-in lenses scan originals with high optical resolution - 6400dpi for film and 4800dpi for photographs. The high optical density of 4.0 DMax allows the scanner to accurately reproduce a wide range of shades, especially in dark areas of the image. High Pass Optics anti-reflective coating on the lens and mirror ensures the best possible image quality.

There are quite a few models of flatbed scanners, and it is important to choose a model that suits your needs so as not to overpay for expensive optics for processing slides if you plan to scan only documents.

Flatbed scanners for business

Business devices are designed for high loads - up to 8000 scans per day! And suitable for processing:

standard paper documentation,
dilapidated or bulky samples (books, magazines),
stapled official documents that cannot be separated.

Another distinctive feature of business scanners is the ability to connect via a network, i.e. the scanner becomes available to several computers in the workgroup at once. There are scanners with built-in interfaces (connectors), or you can separately purchase and connect a special panel with network connectors. With its help, the scanner can be connected via Ethernet and scan to email, an FTP server, Share Point and network folders.

In the line of flatbed scanners for business, for example, the Epson WorkForce DS-7500 scanner with a maximum load of 4000 documents per day will cope perfectly with all the listed tasks. To scan a stack of pages, you can use the 100-sheet duplex automatic document feeder - sensors simultaneously read the front and back sides of the sheet. If stapled or stuck pages are detected, the ultrasonic sensor will notify you of this. Fragile, bulky, or bonded materials must be placed on the glass of the tablet. The optical resolution of this model is 1200 dpi (no more is needed, since documents are scanned, not film or small photographs), and the interpolation resolution is 9600 dpi.

Using software functions it is possible to:

automatically straighten the image,
customize the color palette of the document,
remove shadows from the binding area when scanning books,
Selectively remove red, green, or blue from a document to improve document readability.

Stream scanners

Stream, broaching, roller or as they are sometimes called - document scanners are designed for fast multi-page document processing. A stack of materials is loaded into the automatic feeder and pulled page by page through the matrix. Originals must be opaque (translucent) because they use a method of reflecting light off a surface.

By the way, a fax is a type of streaming scanner.

Despite their compact size (usually small desktop devices), they can work with almost any material from business and plastic cards, to special forms and materials up to 1.5 mm thick and up to A3 size.

Like all flatbed scanners for business, streaming models are equipped with:

ultrasonic sensor for stuck pages,
technology for skipping blank pages,
task breakdown function for saving into different files
automatic system for determining document format,
document tilt recognition and correction system.

Automatic document feeding allows you to scan almost any material in the office in duplex mode on both sides in one pass. Plastic cards (up to 1.5 mm thick), business cards, A4 and even A3 documents and many other materials and documents will be scanned as quickly and efficiently as possible.

Let's talk about the most interesting models of stream scanners for business:

Epson WorkForce DS-560 is Epson's first document scanner with wireless connectivity and Wi-Fi scanning. Moreover, you can scan directly to mobile devices and tablets based on Android and iOS. Processing speed is up to 25 ppm in single-sided mode or up to 50 images per minute in duplex mode at 300 dpi resolution. The scanner supports scanning in color, grayscale or black and white and provides a maximum resolution of up to 600 dpi. The capacity of the automatic document feeder is 50 sheets. The maximum daily load for this model is 3,000 pages.

The flagship of our line of flow scanners is the Epson WorkForce DS-860 with a maximum load of up to 6,000 pages per day (imagine 12 reams of 500 sheets of paper!) and an 80-sheet paper tray. The scanner is capable of processing documents at speeds of up to 65 pages per minute for color and black and white A4 documents or 130 images per minute at a resolution of 300 dpi.

Like most Epson document scanners, the WorkForce DS-860 is available in two versions: with USB connectivity and in a network version.

Double-sided scanning trick

Thanks to double-sided scanning, Epson A4 format stream scanners allow you to obtain a digital copy of a document in A3!

Small, but daring!

For those who, due to their duties, often travel on business trips, the Epson WorkForce DS-30 portable scanner is perfect. It weighs 325 grams. and can easily fit in the same bag along with your laptop. Its dimensions are only 276x36.5x50 mm (length, depth, height), so it can even be hidden in a drawer if there is little work space on the table. Epson WorkForce DS-30 is one of the most compact and lightweight scanners in its class.

It works from a regular USB 2.0 cable connected directly to a computer or laptop. There is only 1 button on the scanner body, but it can be programmed for a number of tasks: specify not only scanning modes, but also mailing addresses for digitized documents and images, insert them automatically into certain applications for further processing.

The standard Epson Scan driver is capable of automatically aligning and determining the document size, enlarging fonts, protecting a PDF file, and also performing other equally important functions.

The Epson WorkForce DS-30 will take 13 seconds to scan an A4 document. And the maximum possible resolution will be 600x600 dpi. In addition, the scanner supports all commonly used paper document formats (A4, A5, A6, A8, B5), and also allows you to digitize business and bank cards.

First I will tell you what a scanner is. A scanner is a device for reading an image and presenting it electronically to a computer. You can scan both photographs and text, which can be recognized by a computer using special text recognition programs. And in this article I will tell you,

How to use the scanner.

You put the scanner on the table and what to do with it?

First, connect it to your computer and install the drivers. I also advise you to install a program that has a scanning function. Most likely such a program is on the driver disk. However, you can use programs such as ABBYY FineReader (Program for scanning and text recognition), (Photo viewer with scanning function) and others. To check whether the program has a scanning function, you can go to menu « File» look in the section « Import"if there is an item whose name matches the model of the connected scanner. that means everything is fine.

Let's launch our program. Open the scanner lid and place a photo or piece of text there. Next, select the scanning function in the program.

A window will open where we will need to click on the “ Preview" Then select the area of the sheet or photo that you want to scan. There is also the ability to set the scanning mode depending on the print quality. You have the choice to scan in color or black and white.

Next you can select the resolution. If you are scanning photographs, I advise you to set the value to a larger value to ensure a good quality image. After you have set all the settings, you can click on the “ Scanning" We are waiting for the scanner to digitize our sheet and transfer its digital copy to our program.

A digital image will appear on the screen that you will need to save or recognize. In order to save our image, select the menu “ File" and click on the button " Save" or " Save How" Now we set the extension and file name. To recognize it, I advise you to use the ABBYY FineReader program. This program has a simple interface: all the necessary buttons are located on the toolbar, and I don’t think it will take long to understand the functionality.

Advice for offices or for people who have several computers and one scanner at home: you can use the scanner over a network. scanning is no different from that described above, you will only need to make a number of preliminary settings. Go to menu " Start» « Control Panel" and select " View networked computers and devices" There, in the list of devices, select the desired scanner model. and everything is ready.

I hope you were able to learn how to use the scanner. Perhaps you will find this article useful

Despite the abundance of photographic equipment with which you can convert any image into digital form, scanners continue to be popular. Thanks to ease of use and high quality of digitization, these devices have become regulars in offices and apartments. Manufacturers produce a huge range of scanners in different price categories. In order not to overpay for unnecessary functions, it is better to understand the basic technical characteristics of these devices in advance.

What is a scanner for?

A scanner is a device that can be used to transfer texts and graphics into digital format. The quality of scanned materials is comparable to original documents, and you can digitize anything from slides to manuscripts and printed books. Thanks to these devices, libraries have appeared on the Internet, in which searching for the necessary information is much easier and faster than in traditional book depositories. Scanners are used almost everywhere:

in offices - for digitizing documents;
in stores - for reading barcodes;
in medical institutions - to convert radiographic images into digital format;
in companies providing photo services - to transfer printed photographs to a hard drive.

Even some smartphone models are equipped with scanner functions. With their help, you can read barcodes and control your own spending. True, such a device is not suitable for serious work with documents.

Scanner selection

Before buying a scanning device, decide for what purpose you need it. Otherwise, there is a risk of overpaying for functions that you will not use. For example, for simple text recognition, a cheap model is sufficient, while expensive wide-format devices are useful only to professionals working with posters and drawings. When choosing a scanner, pay attention to its type, format, resolution, speed, interfaces and availability of additional features. The cost of the device will directly depend on these characteristics.

Types of scanners

Tablets are devices that are similar in appearance to photocopiers. The document is placed on the glass, and the scanning head moves, recognizing texts and images. Using flatbed devices, you can scan documents of different sizes (A3, A5, etc.), including individual sections of texts and photographs. If there is a special module, the device will also be able to recognize slides and films.

Lengthy (streaming)– devices that resemble a fax machine. The sheets of paper in them are pulled one by one using rollers through the scanning device. This device cannot recognize books, magazines or slides: it is only suitable for scanning individual documents. But such models are usually compact and easy to use.

Manual - small devices capable of capturing a fairly small area of documents. Typically, such devices have low resolution. Most often they are used in trade to scan barcodes. You can process a standard document with them only if you have a program in which individual fragments of the whole image are combined.

– expensive devices for scanning slides and photographs. In appearance they resemble table lamps.

Slide – devices that scan slides and photographic films. These are compact but expensive devices that are distinguished by the high quality of the resulting images.

Drums– expensive professional scanners with which you can obtain high-quality images. They have a resolution of at least 8 thousand dpi, while the same figure for budget models is 200-400 dpi.
Planetary (book)– devices designed specifically for scanning books. Recognition is carried out contactlessly, which eliminates mechanical damage to old archival documents. Thanks to the design, there are no dark areas in the folds, which ensures maximum quality of scanned files.

Inexpensive and universal tablet devices are most suitable for home use. LED, fluorescent or xenon lamps can be used as a lighting module. The latter have a long service life, but consume a large amount of energy. Fluorescent lamps are reliable, inexpensive, but take a long time to heat up.

Sensor types

The quality of scanned files depends on the technology used. Most modern devices are equipped with CCD or CIS sensors.
The CCD sensor is used in almost all professional models. Such devices are characterized by high resolution, image clarity and excellent color rendition. The high quality of the scanned material is somewhat offset by the large weight and thickness of the scanners. Devices based on CCD technology require a lot of time to warm up before use.

. Typically, scanners based on this technology are compact and lightweight. They have a high operating speed, consume little electricity and can be powered via a USB port. The disadvantage of such devices is a decrease in sharpness when scanning documents with an uneven surface. Thus, when working with books or wrinkled sheets, the quality of the digital image can greatly deteriorate.

5 main technical characteristics

1. Matrix resolution. The higher this indicator is, the better the quality of the digital image. The technical specifications indicate 2 types of resolution: for example, 1200x1200 dpi and 2400x2400 dpi. The first group of numbers indicates the usual, or real, resolution, which you need to pay attention to when purchasing. The second group shows to what extent the resolution can be artificially increased while losing quality. To scan texts, it will be enough if the optical resolution is within 200-300 dpi, to work with images you need about 600 dpi, and processing slides and then printing them on A4 sheets requires at least 2400 dpi. In the same price category you can find scanners with very different resolutions: in most models it ranges between 600 and 4800 dpi.
2. Scan speed. This setting shows how many pages per minute the device can process. The higher the resolution, the lower the scanning speed will be because the device will take longer to process the image. As a rule, black and white sheets are scanned faster than color sheets, although in some devices these indicators are identical. The average processing speed of b/w sheets ranges from 5 to 45 sheets per minute, it greatly depends on the type of device.

3. Color depth. This value gives an idea of how many colors the device recognizes. Color depth can be internal or external. The first parameter shows how many colors the scanner can distinguish, and the second – how many shades it can transmit to the computer. A color depth of 24 bits is quite enough for normal work with images, so you shouldn’t overpay for a 48-bit scanner, of course, if you don’t plan to print scanned drawings or photos later.
4. Maximum paper size. Most scanner models are designed for the size of a standard A4 sheet. Compact devices can process images whose dimensions do not exceed A6 format. Professional devices are capable of scanning large size sheets, from A3 to A0. The larger format a scanner can process, the higher its price will be.
5. Format of scanned files. Processed images can be output to a computer in several formats: JPG, PDF, TIFF, BMP, RTF, TXT, etc. It is desirable that the scanner can record files with different extensions. This will save the user from additional work of translating into the desired format.

Some scanners are produced for certain operating systems: a device designed for Windows will not work in Mac OS. Before purchasing, find out what OS a particular model is designed for. There are also devices that can work in any system. This characteristic does not depend on the price, but on the brand: some manufacturers produce exclusively multi-system devices.

Scanner interfaces

The scanner can connect to a computer in different ways:

USB– the most popular interface through which scanned images are transferred to a computer, and USB 3.0 allows you to transfer files almost 10 times faster than USB 2.0;
Ethernet (RJ-45) – usually used to connect the scanner to a laptop or local network;
FireWire (IEEE 1394)– high-speed connection, through which professional devices are usually connected;
SCSI– the fastest but most complex way to transfer scanned images;
Wi-Fi– allows all wireless network users to work with the scanner, and the device can be installed anywhere, without being tied to cables.

Some devices also have memory card slots. This increases the cost of the scanner, but allows you to record information directly onto the media, bypassing the computer.

Additional features

Expensive scanner models can be equipped with various useful functions that make using the device more convenient, especially for non-professionals. The following may be very useful:

automatic image processing: removing grain and other defects, adjusting color balance, etc.;
the presence of an adapter and frames in tablet devices for comfortable scanning of slides;
autofeed , which allows you to quickly scan stacks of documents, can be either single-sided or double-sided ;
automatic scanning of books and skipping blank pages;
presence of LCD display;
sending scanned materials to email and cloud services.

The more functions a scanner has, the more expensive it will cost.

Cost of scanners

Prices for scanners start from 1.5 thousand rubles. Budget models are broaching A4 format scanners with CIS sensors, optical resolution of 300-600 dpi and a USB 2.0 connection interface. As a rule, such devices have a one- or two-sided automatic document feeder.
For 3.5-6 thousand rubles. You can buy a pretty decent flatbed scanner with a resolution from 600 to 4800 dpi. Such models are equipped with CIS sensors, can record information in different file formats, and some models are equipped with adapters for processing slides. The cost of professional slide scanners starts from 5 thousand rubles, and prices for camera devices start from 7 thousand rubles.
From 8 to 15 thousand rubles. There are tablet devices that are close to professional ones. Many similar models have CCD-type sensors, auto-feeders, resolutions up to 9600 dpi and the ability to scan slides. Devices capable of scanning images in sizes A2, A1 and A0 cost from 100 thousand rubles. and are purchased for professional use.

To choose the right home scanner, you need to take just two simple steps. Decide what you need a scanner for and select a device with suitable parameters. But to take the second step, you will have to find an advanced user of this technology for consultation or understand the technical part of the problem yourself. It’s the latter that we want to help you with.

Why do you need a scanner in your home?
1.To send a scan of a document by email from time to time. If you are going to do this infrequently and you do not need ideal scan quality, then absolutely any scanner will do, even a used one.
2. As a replacement for a photocopier, that is, to obtain paper copies. If you need one or two pages a week, then printing a scan is easier than looking for a copy shop. For complete comfort, you can buy a device that connects directly to the printer, bypassing the computer, or even prefer an MFP scanner. It is important that printing occurs quickly, and that the software of the scanner itself makes it possible to improve the sharpness of the copy and remove unnecessary details.
3. For storing and processing text information from books, notes and other “paper” sources. If you primarily need to scan texts, and in large volumes, then the key characteristic of the device for you is scanning speed.
4.To organize photographs and other images in home and personal archives. In particular, a huge number of children's drawings can be stored in electronic form. The scanner is also useful for amateur photographers, especially if he sometimes takes pictures with a film camera (or has shot on film before). When scanning images, the resolution of the scanner becomes a significant indicator, especially if you are scanning photographic films.
5.For scanning large objects, which many people consider an exciting hobby. Even pets are placed in the scanners (the procedure is safe). To facilitate this process, we came up with a special volumetric scanner cover.
Reading the technical passport
Let's open the description of any scanner. What does each device parameter mean for the user?
Scanner type: flatbed. 99.9% of home scanners belong to this type, so there is no point in looking for other varieties.
Scanner sensor type. There may be options here: CIS or CCD. CIS is cheaper and, perhaps, more reliable, but CCD gives greater depth of field. If you are scanning mostly texts, depth of field is not important. For images and three-dimensional objects it is very significant.
Document format. For most users, A4 is enough. A3 is needed if you intend to scan patterns, drawings and newspaper strips.
Permission. In modern models it is rarely below 1200 dpi (dots per inch). For scanning text, as well as for scanning images and then printing them on a printer, this is more than enough. Higher resolution (from 4800 dpi) is important for scanning photographic films. The scanner resolution is usually indicated by two numbers: pay attention to the smaller one, and to ensure that we are talking about “optical” and not “hardware” or “improved” resolution. If you are going to scan films, then it is advisable that the scanner not only be highly sensitive, but also have a special slide module (aka slide adapter) with frames for film of the size you need.

Color depth. For a long time there has never been less than 24 bits, which also covers all the needs of a home office.
Scan speed. It is very good for a home scanner if it reads an A4 page in 20–30 seconds (including returning the head to its previous position). On average, manufacturers promise 40–60 seconds per page. This characteristic is the most difficult to understand. Speed is usually expressed in units that require additional calculations: lines per second, or, conversely, milliseconds for a line to pass. Moreover, the full time spent is not always taken into account. So a smart way to choose a really fast scanner is to do a test scan or ask a trusted seller directly.
Connection interface. Most modern scanners connect to a computer via a USB 2.0 port. Sometimes there are several options, but the choice costs a few extra tens of dollars. It is believed that SCSI and IEEE 1394 ports provide slightly higher scanning speeds, but for many they are already occupied by printers or are completely absent from the computer. Before you pay for advanced connectivity, find out whether it's feasible to implement.
Additional options. A scanner with the ability to “scan three-dimensional objects” makes it more convenient to place not only live cats, but also thick books. Although you can scan a book spread with any scanner. The automatic sheet feed function is useful if you have to scan large volumes of text on separate sheets of paper (the scanner still cannot leaf through a book on its own).

Comparison task
Let's say that in a store window you were attracted by the Epson Perfection V330 Photo (one of the most popular among buyers, priced from $130) and Canon CanoScan LiDE 110 (sold for $90 and also released under a reputable brand). What to choose?
If you are an amateur photographer, and even keep an archive of photographic films, then, most likely, you will find yourself with the majority of buyers. Epson's high level of optical resolution (4800x9600 dpi), sensitive CCD sensor, 48-bit color depth and the presence of a slide adapter speak in favor of Epson as a device for accurately transmitting even small image details. We are also pleased to have built-in software for correcting sharpness and removing noise from photos.
But when choosing a scanner for texts, you are more likely to pay attention to a cheaper model from Canon. The scanning speed clearly indicated in the specification is 3.7 ms per line (at 300 dpi) after recalculation gives 13–14 seconds per A4 page. That's even faster than the 16 seconds Epson promises. A simpler CIS sensor for a text scanner is not a minus, but a plus: the simpler the device, the less often it breaks. At the same time, the optical resolution of 2400x4800 dpi available to the scanner allows it to be used for scanning images. The capabilities of a Canon scanner are not enough for high-quality scanning of photographic film - but who said that you were going to scan it?