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Digitization Speed

One of the key characteristics of any scanner is its ability to quickly process originals of any degree of complicity. Requirements to the speed qualities of the scanner are high, but if I’m not mistaken they are not regulated by any official norms and standards. This may be the reason for the manufacturers to declare only those speed values which won’t shock the potential buyer. The digitization speed of a scanner depends on several factors. I’ll try to enumerate them.

The configuration of the system the scanner is attached to is of highest importance. The amount of main memory and the free disk space are both very important. To improve performance you’d better place a second hard disk drive on the second IDE channel for it to receive the digitization data.

The type of the interface to the computer is also a key contributing factor to the scanner’s digitization speed. All modern devices are equipped with high-speed USB 2.0 and FireWire ports so you should make sure your system has them. I think a FireWire connection is preferable as it doesn’t require a controller (FireWire works by the “peer-to-peer” principle) and consumes fewer resources than a USB connection.

The third factor is the speed of the scanner proper. It greatly depends on the light source employed in the particular scanner. Traditional mercury lamps used in a majority of SOHO scanners need additional time to warm up. This time is necessary for the mercury to transform from liquid into gas for the light to be evenly distributed. To my regret, the EPSON Perfection 4870 uses such a lamp, too. There is an alternative to mercury – xenon lamps – and maybe we’ll see one employed in the next top model from EPSON?

Now, let’s get back to our tests. After the user activates scanning software, the machine should carry out the pre-scan operation. The lamp warm-up time is about 25 seconds in this phase.


The mercury lamp may take from
25 seconds to 2 minutes to warm up

The lamp warm-up time may differ greatly between the tasks. For example, this time is much higher for scanning transparent originals. Note that when you are scanning using Digital ICE technology, the lamp warms up several times, which results in a much higher overall scanning time.

Speeds of digitizing different originals

 

300dpi

600dpi

4800dpi

6” x 4” (152 x 102 mm) photo

12s / 1m 30s

23s / 1m 35s

11m 45s / 12m 20s

35mm film

18s / 1m 55s

25s / 2m 20s

1m 40s / 8m 20s

A4 size (210 x 287 mm) photo

38s / 3m 25s

50s / 3m 45s

- / -

I measured the digitization speed in three resolutions: 300, 600 and 4800dpi. As you see, the table shows two values for each mode – the second value is measured with Digital ICE enabled. I didn’t perform the measurement for the A4 original at the optical resolution, because this operation would not only require about 3.5GB of disk space, but would also take much time. This phase of my testing was too long as it was, so I didn’t scan originals of other types and formats.

By the way, you can calculate with some precision the size of the file you receive at high resolutions. Use the following formula:

S = k∙L∙H∙R­­2,

where S is the image size (in bytes), L is the length of the original (in inches), H is the height of the original (inches), R is the scanning resolution (dpi) and k is a fixed coefficient. This k equals 3 for the Color scanning mode, k = 1 for the Gray mode and k = 0.125 for the LineArt mode.

 
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