Comparison Epson Perfection V19 vs HP ScanJet 200

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.

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.

By default, the scanner is designed to work with reflective, i.e. opaque materials (such as paper). The slide module allows you to use the device for processing transparent materials, such as photographic film.