Comparison Epson Perfection V39 vs Canon CanoScan LiDE 300

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.

The maximum optical density of a dark image that the scanner can distinguish from pure black. Optical density characterizes how much of the light falling on the image was reflected (for opaque images) or transmitted (for transparent). The higher the optical density, the less light the object reflects / transmits. Accordingly, the higher the optical density of the scanner, the higher its sensitivity and the better it is suitable for working with dark images.

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.

— From the network. The most common option is to connect to a conventional 230 V power supply. This power supply provides enough power to operate any, even the fastest and most performant scanners. Its disadvantage is, in fact, the need for an electrical network.

— From USB. Powered via USB port — the same through which it connects to the computer. This significantly increases the battery life of the scanner — in particular, it can be used with a laptop in places where there is no access to a 230 V network, which is especially important for portable models (see "Portable Design"). On the other hand, the performance of such devices is usually low, and the power of the USB port is not always enough for power supply (which is especially true when using USB hubs).

— Autonomous. Power supply of the scanner from its own batteries (accumulator or replaceable batteries). Such models are as autonomous as possible, because do not require a power cord to operate, and many of them are able to act as separate devices without being connected to a PC at all. Their disadvantage is the risk of switching off at the most inopportune moment due to the exhaustion of the charge — then you have to either change the batteries (which at least requires fresh ones) or recharge the battery (which takes time).

The maximum power consumed by the scanner during operation. The higher the power, the more energy the scanner consumes, but this only applies to the scanning process itself — in standby mode, power consumption is negligible. And even at the peak in most models, the power is so low that in fact this parameter has practically no effect on electricity bills and is more of an auxiliary value (for example, it is used to calculate the total power of devices connected to an uninterruptible power supply).