What determines the optical resolution of a scanner? Scanner resolution - what is the optimal value? When you need high resolution

All digital images can be described by several characteristics that define them physical size(number of bits of memory required to store an image file) and quality. These characteristics are interrelated. For example, the higher the quality of the photograph, the larger size file in which it is stored. In order to determine what quality is associated with digital image You need to become familiar with concepts such as resolution and graphic formats.

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A digital image is made up of tiny elements called pixels. Pixel is the main element (building block) raster images. This unit, adopted in computer graphics, similar to the usual meter, kilogram or liter in Everyday life. It is the number of pixels in the image that is denoted by the term permission.

The higher the resolution, the more pixels the image contains and, accordingly, the higher the quality of the image, since an image with a higher resolution has more detail.

When scanning as well as shooting digital camera or a video camera converts an analog image into digital form (digitization). Currently, touch devices are mainly used for this purpose.

Sensors are integrated circuits that implement a set of photosensitive elements, structurally made in the form of rulers (as in flatbed scanners) or matrices (as in the case of digital cameras). How more quantity elementary photosensitive elements in the sensor, the greater the resolution it provides.

Sensors with a small number of photosensitive elements do not provide high-resolution images. In such an image, individual elements (pixels) can be visible to the naked eye, which leads to the appearance of steps, i.e. effect pixelation(Fig. 2.4).

And vice versa, a large number of very small light-sensitive elements allows you to obtain digital model images close to the original. IN technical documentation for the operation of scanners, the number of dots per inch (dots per inch) is usually used as a unit that determines their resolution. That is, when setting the scanning mode, you must specify scanner resolution in these units, for example, 300 dpi.

NOTE

In the literature, instead of the term dpi (dots per inch), you can find the term ppi (pixels per inch) - pixels per inch. A point is shaped like a circle, and a pixel is shaped like a square. However, in order to avoid terminological confusion in the future, we will consider the resolution units ppi and dpi to be synonymous.

Optical (physical) and software (interpolation) resolution

Optical resolution indicates the actual number of photosensitive elements per square inch (1 inch = 2.54 cm).

Interpolation resolution is not a physical characteristic digital device, but by the characteristics of its software. Therefore, the quality of images obtained using interpolated resolution depends on the quality of the interpolation algorithms implemented in the program.

For example, the scanner passport may indicate an optical resolution of 1200 dpi, and a software resolution of 24000 dpi..

NOTE

Many professional photographers have a negative attitude towards increasing the resolution of photographic images not by hardware, but by software, since when the resolution is reduced, the data is discarded, and when the resolution is increased, the program “invents” them. In other words, interpolation artificially adds elements to a digital image, but does not increase the amount of detail in the image.

Monitor resolution

The resolution of a monitor is related to the maximum number of dots it can generate and their size, and is measured by the number of dots in one horizontal line and the number of horizontal lines of the screen. With the typical dot size ("grain") of 0.2 mm today, the standard resolution for 17-inch monitors is 1024x768.

Printer resolution

The resolution of a laser printer is determined by the number of dots the printer can print on one inch (dpi - dots per inch). So, if a laser printer has a resolution of 300 dpi, then it can print 300 dots in one inch.

You can see the resolution of the printer you have installed by executing the Start Control Panel Printers and Faxes command (Fig. 2.5).

Digital Camera Resolution

In a digital camera, the light passing through the lens hits a light-sensitive matrix (taking the place of the film) - a set of CCD (CCD) or CMOS (CMOS) sensors, which digitize the image. When an image from a digital camera is digitized, the information it contains is converted into a set of numbers organized in a matrix called bit matrix(bitmap). In this case, each photocell of the sensor corresponds to a certain numerical element in the bit matrix.

The light-sensitive matrix (sensor) is the main (and most expensive) component of a digital camera. The quality of the image captured by the camera depends mainly on the resolution of the sensors and the quality of the camera optics.

IN digital cameras The basic unit of measurement for resolution is the pixel, and its value is determined by the size of an individual CCD cell.

For images entered into a computer using a digital camera, the resolution can be specified either as a specific number of megapixels (a megapixel sensor contains 1 million photosensitive cells) or as a raster image with a specified number of horizontal and vertical pixels. For example, a digital camera with a 2.1 megapixel sensor creates an image file of 1792*1200 pixels (saved in JPEG format).

Graphic formats

After the frame is in digital camera taken, the resulting image must be recorded in memory. Graphic formats are most often used for this. JPEG or TIFF. Moreover, for a photographer, the recording format is not so important as the capabilities of the compression modes used in them (preferably with minimal loss of quality), as well as the amount of memory in the camera. Let's talk about this in more detail.

Each of the formats existing today has undergone natural selection and has proven its viability and practical value. They all have characteristics and capabilities that make them indispensable in specific areas of application: Web design, printing, photo retouching and others.

The entire variety of formats used for recording images can be divided into two categories:

• storing the image in raster form (BMP, TIFF, JPEG, PNG, GIF, etc.);
• storing the image in vector form (WMF, CDR, AI, FH9, etc.);

Which format should you prefer? Professionals know that it is better to save their work in a format that is “native” to the program they are using. For example, in Photoshop - PSD, CorelDRAW - CDR, Flash - FLA. This will allow maximum degree realize the program's capabilities and insure against unpleasant surprises. However, in this lecture we will pay attention mainly to raster formats, since we have to work with photography in raster formats. graphic editors.

Raster formats

A raster image (raster) resembles a grid (table) of pixels, which in its simplest black and white version consists of two types of cells: white or black, and which can be encoded, respectively, with a zero or a one. Unlike black and white, in a color RGB image, for example, 24 bits deep, each pixel is encoded with a 24-bit number, so each cell of the bit matrix stores a number of 24 zeros and ones.

Now let's move on to consider the most common raster image formats.

BMP

The BMP format (from the word bitmap) is native format Windows. It is supported by all graphic editors running this operating system. Used to store bitmap images for use in Windows, for example as your desktop background. With this format you can set the color depth from 1 to 24 bits. Provides the ability to apply information compression using an algorithm

Scanner- this is a device that, by analyzing any object (usually an image, text), creates digital copy object images. The process of obtaining this copy is called scanning.

In 1857, the Florentine abbot Giovanni Caselli invented a device for transmitting images over a distance, later called the pantelegraph. The transmitted image was applied to the drum with conductive ink and read using a needle. In 1902, the German physicist Arthur Korn patented photoelectric scanning technology, which later became known as telefax. Transmitted image was fixed on a transparent rotating drum, a beam of light from a lamp moving along the axis of the drum passed through the original and through a prism and lens located on the axis of the drum hit the selenium photodetector. This technology is still used in drum scanners. Later, with the development of semiconductors, the photodetector was improved and invented tablet method scanning, but the principle of image digitization remains almost unchanged.

Main characteristics of scanners

Optical resolution

This is the main characteristic of the scanner. The scanner does not take the entire image, but line by line. A strip of light-sensitive elements moves along the vertical surface of the flatbed scanner and captures the image point by point, line by line. The more photosensitive elements a scanner has, the more points he can take off from everyone horizontal stripe Images. This is called optical resolution. It is determined by the number of photosensitive elements (photosensors) per horizontal inch of the scanned image. It is usually calculated by the number of dots per inch - dpi (dots per inch). The normal level of resolution is at least 600 dpi; increasing it even further means using expensive optics, expensive photosensitive elements, and increasing scanning time. Processing slides requires more than a high resolution 1200 dpi.

X resolution

This parameter shows the number of pixels in the photosensitive line from which the image is formed. Resolution is one of the main characteristics of a scanner. Most models have an optical scanner resolution of 600 or 1200 dpi (dots per inch). It is enough to obtain a high-quality copy. For professional image work, higher resolution is required.

Y resolution

This parameter is determined by the stroke of the stepper motor and the accuracy of the mechanics. The mechanical resolution of the scanner is significantly higher than the optical resolution of the photo ruler. It is the optical resolution of the photocell line that will determine the overall quality of the scanned image.

Scan speed

The scanning speed depends on the scanning resolution and the size of the original. Typically, manufacturers indicate this parameter for A4 format. Scanning speed can be measured in pages per minute or the time it takes to scan one page. Sometimes measured in the number of lines scanned per second.

Color depth

As a rule, manufacturers indicate two values ​​for color depth - internal depth and external. Internal depth is the ADC bit depth ( analog-to-digital converter) of the scanner, it indicates how many colors the scanner can distinguish in principle. External depth- this is the number of colors that the scanner can transmit to the computer. Most models use 24 bits for color reproduction (8 for each color). For standard tasks This is quite enough in the office and at home. But if you're going to use the scanner for serious graphics work, try to find a model with a large number discharges.

Maximum optical density

The maximum optical density of the scanner is the optical density of the original, which the scanner distinguishes from “complete darkness”. The higher this value, the greater the sensitivity of the scanner and the higher the quality of scanning dark images.

Light source type

Xenon lamps are characterized by short warm-up time, long service life and small size. Cold cathode fluorescent lamps are cheap to produce and have a long life. Light emitting diodes (LED) are small in size, low power consumption and do not require warm up time. But in terms of color rendering quality, LED scanners are inferior to scanners with fluorescent and xenon lamps.

Scanner sensor type

Scanners and MFPs typically use one of two types of sensors, based on different technologies:

• CIS- Contact Image Sensor / contact image sensor;
• CCD- Charge-Coupled Device / device with charge coupled(CCD).

CIS is a line of photocells that is equal to the width of the surface being scanned. During scanning, it moves under the glass and, line by line, transmits information about the image on the original in the form of an electrical signal. For lighting, LEDs are usually used, which are located in close proximity to the photo ruler on the same movable platform. CIS-based scanners have a simple design, thin body and low weight, which makes the scanner thinner and lighter compared to scanners with CCD sensors. CIS scanners are generally less expensive than CCD scanners. The main disadvantage of CIS is its shallow depth of field.

Photosensor based CCD- this is a specialized analog integrated circuit, consisting of photosensitive photodiodes, made on the basis of silicon, using CCD technology - charge-coupled devices.

The CCD matrix consists of polysilicon separated from the silicon substrate, in which, when voltage is applied through the polysilicon gates, the electrical potentials near the electrodes change. Before exposure, usually by applying a certain combination of voltages to the electrodes, all previously formed charges are reset and all elements are brought into an identical state. Next, the combination of voltages on the electrodes creates a potential well in which electrons formed in a given pixel of the matrix as a result of exposure to light during exposure can accumulate. The more intense the light flux during exposure, the more electrons accumulate in the potential well, and accordingly, the higher the final charge of a given pixel.
After exposure successive changes The voltages on the electrodes form a potential distribution in each pixel and next to it, which leads to the flow of charge in a given direction, to the output elements of the matrix.

Types of scanners

• flatbed scanners are the most common type of scanners because they provide maximum convenience for the user - high quality and acceptable scanning speed. It is a tablet with a scanning mechanism inside under transparent glass.
• manual - they do not have a motor, therefore, the user has to scan the object manually, its only advantage is its low cost and mobility, while it has a lot of disadvantages - low resolution, low speed, narrow scanning band, image distortions are possible, since it will be difficult for the user to move constant speed scanner.
• sheet-pulling (pulling) - a sheet of paper is inserted into the slot and pulled along guide rollers inside the scanner past the lamp. It is smaller in size compared to a flatbed, but can only scan separate sheets, which limits its use mainly to company offices. Many models have a device automatic feeding, allowing you to quickly scan a large number of documents.
• planetary or book scanners - used for scanning books or easily damaged documents. When scanning there is no contact with the scanned object (as in flatbed scanners). Book scanners - designed for scanning bound documents. Scanning is done face up - so your scanning actions are indistinguishable from turning pages during normal reading. This prevents damage and allows the user to see the document while scanning.
• slide scanners - as the name implies, they are used for scanning film slides, produced as independent devices, and in the form of additional modules for conventional scanners.
• Barcode scanners are small, compact models for scanning product barcodes in stores.

Operating principle

The object to be scanned is placed on the glass of the tablet with the surface to be scanned down. Under the glass there is a movable lamp, the movement of which is controlled by a stepper motor. The light reflected from the object, through a system of mirrors, hits the sensitive matrix, then to the ADC and is transmitted to the computer. For each engine step, a strip of object is scanned, which are then combined software into the overall image.

The image is always scanned in RAW format- and then converted to normal graphic format using current settings brightness, contrast, etc. This conversion is carried out either in the scanner itself or in the computer - depending on the model of the particular scanner. The parameters and quality of RAW data are affected by scanner hardware settings such as sensor exposure time, white and black calibration levels, etc.

Ensuring sufficient optical density (shading) of characters and images on the page is important factor V subjective assessment print quality. Disturbances in the electrophotographic process can cause unwanted variations in the darkness (shading) of the image. These deviations may be within or outside acceptable limits. The value of these permissible deviations is set in technical conditions on Consumables to a specific device and may differ significantly for different devices. An objective assessment of the filling density characterizes the heterogeneity of the process and is defined as the limit and standard deviation of the reflection coefficient of a printed character across the page.

The term optical density is used to characterize the measure of light transmission for transparent objects and reflection for opaque objects. Quantitatively defined as the decimal logarithm of the reciprocal of the transmittance (reflection). In electrography, this term is used to assess the quality of image elements in copies obtained under certain development conditions (using a certain type of toner, assessing the contrast value of a latent electrostatic image, the quality of copies when using a particular development method, etc.). In printing, this characteristic is used to evaluate publishing originals, intermediate images and prints.

Optical density is designated OD (Optical Density) or simply D. The minimum optical density value D=0 corresponds to white color. How more light absorbed by the medium, the darker it is, i.e., for example, black has a higher optical density than gray.

Reflectance is related to optical density and contrast density as follows:

D = log (1/R pr) and D c ​​=R pr /R pt

where D is the optical density of the image;

R pt - reflection coefficient at the measurement point;

D c - contrast density;

R pr - paper reflection coefficient.

The values ​​of the optical density of the image on copies for black in electrography for different devices (as noted above) are significantly different. Typically according to the toner manufacturer's specifications for laser printers these values ​​(the minimum permissible in the normal state of the equipment) lie in the range from 1.3D to 1.45D. For high-quality toners, optical density takes values ​​in the range from 1.45D to 1.5D and does not exceed 1.6D. In technical specifications, it is customary to set restrictions on the lower permissible limit with a standard deviation in optical density of 0.01.

The optical density value is measured special device- a densitometer, the operating principle of which is based on measuring the flux reflected from the print and converting this indicator into units of optical density.

In electrography, the optical density of images is used to characterize the developer (toner) in order to determine the required values ​​of the optical density of lines of a set width under certain development conditions or to characterize the electrophotographic image on copies in the nominal operating mode of the equipment

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image details and smooth color transitions in dark and light areas are lost. Resolution or scanner resolution - a parameter characterizing the maximum accuracy or degree of detail in the representation of the original in digital form . Resolution is measured in pixels per inch

(pixels per inch, ppi). Resolution is often indicated in dots per inch (dpi), but this unit of measurement is traditional for output devices (printers). When talking about resolution, we will use ppi. There are hardware (optical) and interpolation resolutions of the scanner.

Hardware/optical Resolution is directly related to the density of photosensitive elements in the scanner matrix. This is the main parameter of the scanner (more precisely, its optical-electronic system). Usually the horizontal and vertical resolution is specified, for example, 300x600 ppi. You should focus on a smaller value, i.e., horizontal resolution. The vertical resolution, which is usually twice the horizontal resolution, is ultimately obtained by interpolation (processing the results of direct scanning) and is not directly related to the density of the sensitive elements (this is the so-called double step resolution).

To increase the scanner resolution, you need to reduce the size of the photosensitive element. But as the size decreases, the element’s sensitivity to light is lost and, as a result, the signal-to-noise ratio deteriorates. Thus, increasing resolution is a non-trivial technical challenge.

Interpolation resolution Interpolated Resolution - image resolution , obtained as a result of processing (interpolation) of the scanned original. This artificial resolution enhancement technique usually does not result in an increase in image quality. Imagine that the actually scanned pixels of the image are moved apart, and “calculated” pixels are inserted into the resulting gaps, similar in some sense to their neighbors. The result of such interpolation depends on its algorithm, but not on the scanner. However, this operation can be performed using a graphic editor, for example, Photoshop, and even better than the scanner's own software. Interpolation resolution, as a rule, is several times higher than the hardware resolution, but practically this means nothing, although it may mislead the buyer.

Significant parameter

is the hardware (optical) resolution.

The scanner's technical data sheet sometimes simply indicates the resolution. In this case, we mean hardware (optical) resolution. Often both hardware and interpolation resolutions are specified, for example, 600x 1200 (9600) ppi. Here 600 is the hardware resolution, and 9600 is the interpolation resolution. parallel lines per inch, which are reproduced by the scanner as separate lines (without sticking together). This parameter characterizes the scanner's suitability for working with drawings and other images containing many small details. Its value is measured in lines per inch (Ipi).

What scanner resolution should you choose?

This question is asked most often when choosing a scanner, since resolution is one of the most important scanner parameters, on which the ability to obtain high-quality scanning results significantly depends. However, this does not mean that you should strive for the highest possible resolution, especially since it is expensive.

When developing scanner resolution requirements, it is important to understand the general approach. A scanner is a device that converts optical information about the original into digital form and, therefore, performing its sampling. At this stage of consideration, it seems that the finer the sampling (the greater the resolution), the less loss of the original information. However, the scan results are intended to be displayed using some output devices
So, there is an original with its own resolution, a scanner with its own resolution, and a scanning result, the quality of which should be as high as possible. The quality of the resulting image depends on the set resolution of the scanner, but up to a certain limit. If you set the scanner resolution to be higher than the native resolution of the original, then the quality of the scanning result, generally speaking, will not improve. We don't mean to say that scanning at a higher resolution than the original is useless.

There are a number of reasons when this needs to be done (for example, when we are going to enlarge the image for output to a monitor or printer, or when we need to get rid of moire). Here we draw attention to the fact that improving the quality of the resulting image by increasing the scanner resolution is not unlimited. You can increase the scanning resolution without improving the quality of the resulting image, but increasing its volume and scanning time. We will talk about choosing the scanning resolution many times in this chapter. Scanner resolution is maximum resolution
, which can be set when scanning. So how much resolution do we need? The answer depends on what images you want to scan and what devices you want to output to. Below we provide only approximate values.

If you are going to scan images for subsequent display on a monitor screen, then a resolution of 72-l00ppi is usually sufficient. For output to a regular office or home inkjet printer - 100-150 ppi, to a high-quality inkjet printer - from 300 ppi. When scanning texts from newspapers, magazines and books for subsequent processing by programs optical recognition

characters (OCR - Optical Character Recognition) usually requires a resolution of 200-400 ppi. For display on a screen or printer, this value can be reduced several times.

For amateur photographs, 100-300 ppi is usually required. For illustrations from luxury typographic albums and booklets - 300-600ppi.

Advertising agencies, for example, require high-quality scanning of slides and paper originals. When scanning slides for printing in 10x15 cm format, you will need a resolution of 1200 ppi, and in A4 format - 2400 ppi.
Summarizing the above, we can say that in most cases, a scanner hardware resolution of 300 ppi is sufficient. If the scanner has a resolution of 600 ppi, then this is very good.

A scanner is a device that allows you to enter information into a computer graphically text, drawings, slides, photographs, graphs, articles, manuscripts, etc. All scanners can be divided into several classes: hand-held (extended), desktop or tablet, scanners for transparent materials. The main differences between the devices are cost, image quality and method of use.

Scanners belong to SAD systems (Source Attenuator Detector - attenuation source detector, or change detection tool). As light in the scanner reflects off or passes through the document, the amplitude of the light signal will weaken slightly, which will be detected by the scanner's sensors, which measure the difference between the light values. Eat different kinds sensors Most skers use CCD sensors (Charged-coupled devices) - charge-coupled devices or charge-coupled devices (CCDs) that convert light into piels. Each scanner has a line array consisting of several thousand CCD devices arranged in a row along the scanning engine. Some scanners use complementary metal-oxide semiconductor (CMOS) sensors, which first appeared in digital cameras. CMOS devices differ from CCD sensors in that they exist as a separate unit. CCD and CMOS devices compare the value during scanning electric charge before and after its reflection from the scanned original. The difference is converted into a hue and determines the color of the pixels.

Scan speed- one of the characteristics of the scanner.

Scanning time starts by pressing the button Scan and ends at the moment when the image is available for editing in Adobe Photoshop. If scanning is performed with the autocalibration mode enabled, which is performed before each scan, then the scanning time increases by 6-8 s.

Research shows that scan time with resolutions of 1200 and 2400 dpi turned out to be the same, which suggests that the vertical resolution, which many manufacturers Lately for advertising purposes, they say twice as large as horizontally - most likely, it’s just interpolation resolution, and the number 2400 only indicates improved scanner mechanics.

Modern scanners have quite a large memory buffer: when scanning pictures of 50 MB in size while parking the ruler (movement of scanning devices in initial position) the scanner continues to calculate and transmit the image.

Dynamic range- one of the most important parameters of the scanner. The dynamic range is calculated by the formula: D = Dmax – Dmin, where D is the difference between the maximum and minimum optical densities distinguished by the scanner. Typically, the minimum optical density Dmin perceived by the scanner is 0.07-0.08 D.

Optical density equal to the negative decimal logarithm of the reflection (transmission) coefficient. If the optical density is 1, 2, 3, etc., then one tenth, hundredth or thousandth of the incident light is reflected (or transmitted), respectively. On transparent visual materials (slides) and photographs, the optical density can reach 4.0.

Scanner optical resolution

The main characteristic of the scanner is optical resolution. It is measured in ppi - pixels per inch; however, it is often written dpi - dots per inch. The term "dot" means an element that does not have a specific shape and is used to measure the resolution of printing devices. Scanners and raster graphic files operate with pixels that are always square in shape.

Optical resolution indicates how many pixels the scanner can count in a square inch. It is written like this: 300´300, 300´600, 600´1200, etc. The first number indicates the number of sensors reading the information, and this is what you should pay attention to. Often manufacturers and sellers like to indicate something like 4000, 4500 dpi in the resolution. This interpolated solution is not a property of the scanner, but of the program that supports it. The quality of images obtained in this way depends not only on the scanner, but also on the quality of the interpolation functions implemented in the program.

Of course, scanning the maximum range of optical densities is not at all necessary, and sometimes not desirable - for normal, not test scanning.

Another unit of measurement of optical resolution is spi (samples per inch) - the number of samples taken by the scanner in one inch. In this case, the resolution indicates how many times the scanner looks at the image when scanning. If the line array of a flatbed scanner has 600 tiny sensors in a row on every inch, then the optical resolution of the scanner is 600 spi.

Optical resolution in dpi is usually indicated by scanner manufacturers, although it is more logical to indicate it in spi.

Hello, dear readers of the blog about. Today we will talk about this important parameter scan like permission. Resolution determines the amount of detail recorded. It is measured in dots per inch (dpi). The higher the dpi value, the higher the resolution.

Image quality improves with increasing resolution, but only up to a certain point, after which further increasing the resolution only leads to the fact that the file becomes too big size so that it can be controlled. In addition, images with higher resolution take longer to print. In most cases, 300 dpi is more than enough resolution for scans.

Talking about scanner resolution, we should not forget the difference between optical resolution and interpolation. Optical resolution is “native” to the scanner and depends on the optics used in the device’s design. Interpolated resolution is resolution increased by special programs. And while interpolation can be useful in some cases (for example, when scanning graphic drawings or when you need to enlarge an image small size), the quality and clarity of the image obtained in this way is lower than when using only optical resolution.

How to choose the optimal resolution settings?

Scanning at high resolution requires more time, memory and disk space. When setting resolution settings, take into account the type of image and the printing method you intend to use later or the output device.

The easiest way to determine the required resolution is to find out the number of lines per inch (lpi value) of the image output device and, to be more accurate, multiply this number by two.

Example: To “fit” a scanned image to a standard magazine press with an lpi value of 133, simply multiply 133 by 2. The result will be an optimal resolution of 266 dpi. However, if you plan to enlarge the image after scanning, remember that this will reduce the resolution, so be careful with scaling.

The lpi number varies depending on the print quality. A newspaper needs approximately 85 lpi, a magazine needs 133-150 lpi, and a color book may need 200 to 300 lpi.

If you are displaying images on a monitor (for example, for publishing on the Internet), there is no need for a resolution of more than 72 dpi, since monitors are not capable of displaying more than 72 dpi. Image higher resolution will not get better or clearer; it will only increase the file size, making it more difficult to process.

Remember that the higher the resolution, the larger the file size. For example, color photo format 8.5 by 11 inches with a resolution of 72 dpi will “weigh” approximately 1.6 megabytes. Increasing the resolution to 150 dpi will increase the file size to 6.3 megabytes (about four times)! And at 300 dpi, the same file will already “weigh” 26.2 megabytes.

Thus, you should always try to choose the lowest resolution possible in order to maintain image quality and at the same time, not get too large for convenient use file.

When do you need high resolution?

High resolution is important when you pass the image through a high-tech color management system, which retains all the data obtained during the scanning process when printing. In this case, high resolution will make the final image clearer and sharper.

When to use an interpolated image?

The interpolation function is useful for scanning graphics and pencil drawings, as well as to enlarge small images. Also included in this category are any black-and-white or one-color graphics, ink or pencil sketches, sketches, or mechanical blueprints.

For graphics: set the resolution equal to the resolution of the printing device. For example, if you are going to print an image on a device at 1200 dpi, set your scanner to 1200 dpi for optimal results. This will ensure smoother lines and eliminate unevenness and blurriness.

To enlarge small originals: Let's say you're scanning a 1- or 2-inch photo at 300 dpi, and the scanner's maximum optical resolution is also 300 dpi. To enlarge an image twice the size of the original without losing detail, interpolate the image to 600 dpi. This way, the image will remain sharp and clear, and its size will double.