Comparison HP ScanJet Pro 3500 f1 vs HP ScanJet N6310

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.

— CIS, abbreviation for "Contact Image Sensor" — contact image sensor. The simplest type of optical element: it is a line across the entire width of the scanner's working space, on which photocells that read the image and LEDs that provide illumination are located in a row. They are inexpensive and take up little space, which, accordingly, makes the scanners themselves cheaper and smaller. On the other hand, CIS sensors have a shallow depth of field, and even small bumps in the scanned image can be out of focus. However, in general, they are quite suitable for both personal and not too complex professional tasks.

— CCD, short for "Charge-Coupled Device" — a charge-coupled device. A much more complex design than CIS, includes a fluorescent lamp, lens and mirror. CCD scanners are larger, heavier and much more expensive than their counterparts in CIS. On the other hand, this type of optical element provides high-quality colour reproduction and a good depth of field, coping well with complex-shaped media. Therefore, advanced professional scanners are usually equipped with a CCD.

— CMOS. The abbreviation for "Complementary Metal-Oxide-Semiconductor" is a complementary metal-oxide-semiconductor structure (the designation CMOS is also used in Russian). A key feature of CMOS sensors is that they capture the scanned image as a whole, similar to photography (and not...line by line, as in other types of optical elements). In fairness, it should be noted that the "instantaneous" scanning does not give a tangible advantage in speed, because. processing the captured image takes quite a long time. However, this feature is extremely useful in cases where it is difficult to ensure the immobility of the scanned material and/or uniform movement of the optical element relative to this material. Such situations often arise when working with book and handheld scanners (see "Type"), so CMOS elements are most popular in such devices.

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.

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.

External colour depth characterizes the maximum possible number of colour shades in the image transmitted by the scanner to the computer. A depth of 24 bits is considered quite enough for non-professional tasks, in more advanced models this parameter can reach 96 bits. For details on colour depths and their relationship, see "Colour Depth (Int.)"

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 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.

The maximum number of pages that the scanner can process per day without overloading and the negative consequences associated with them. Most often indicated for A4 format. Even the most modest models of modern scanners have duty cycles measured in dozens of pages, which is quite enough for simple everyday tasks. Therefore, you should pay attention to this parameter if you have to scan numerous materials every day.

Availability of duplex scanning function in the device. Duplex scanning in this case means such an operating mode in which the scanner simultaneously captures an image from both sides of the processed medium (sheet of paper). The convenience of this feature is obvious: the media does not have to be turned over to scan each side separately, and the processing time is significantly reduced. Double-sided scanning is found mainly in the models of traction or combined type (see above), however, there are also flatbed scanners with this capability.