The unit "dpi" stands for "dots per inch (2.54 cm)." A high number of data dots in the width of an inch means that a scanner's image input will be extremely precise, picking up even the smallest details from the original image.

In the case of Canon's D2400U-series scanners, the significance of 2400 dpi can be demonstrated using a handheld calculator. Scanning the short side of an A4-size sheet of paper at 2400 dpi translates into about 19,000 dots of data in a row. The scanner's specifications note a resolution of 4800 dpi in the vertical direction, equivalent to about 56,000 dots.

Multiplying the number of dots scanned in the horizontal and vertical directions produces the result of approximately 1.1 billion dots per A4-size page, each of which is color classified and turned into data by the scanner.

This total per single page is slightly less than the population of the People's Republic of China, and just a tad more than that of India. Imagine a single point of data for every person in these countries....

Need another example? Well, take a look at your average soccer ball. At 20 cm in diameter, you would need more than 53km2 of space, or about 7,400 playing fields to fit the same number of soccer balls as there are points of data scanned by these products. By the way, that is also roughly equal to the area of the Bermuda Islands. Now you are starting to get the idea of the power of a high-resolution image scanner.

But the scanner's job is not simply to count dots. These devices work with full-color information, separating out an image's red, blue and green colors into the appropriate data values for each color. In the case of the D2400U series, information for each color is input at 16 bits of data. In other words, up to 216 dots for each color, equal to a value from 0 to 65,536, can be precisely scanned in one pass of the scanner.

You probably never considered the mind-bending precision, data volume and scale of the work done by a little flatbed scanner that sits on the corner of your desk.