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Testbed and Methods

We’ll use our traditional methodology to test the following aspects of the EPSON Perfection 4990 scanner:

  • Speed: we’ll measure the time it takes to scan typical originals
  • Noise tolerance: we’ll calculate the image noise coefficients for the scanned images and evaluate the tolerance of the scanner’s electronics to interference
  • Resolution: we’ll check the scanner’s modulation transfer function
  • Color reproduction: we’ll determine the scanner’s gamut range with opaque and transparent originals, build color discrepancy diagrams and visually evaluate the scans.

We use one and the same computer for testing scanners in our labs. Its configuration always remains like follows:

  • Intel Pentium 4 3.0GHz
  • 1GB DDR SDRAM
  • Intel Bonanza D875PBZ mainboard
  • ATI RADEON 7000 graphics card
  • IBM DeskStar DTLA307015
  • Samsung SyncMaster 757 NF
  • Microsoft Windows XP Professional SP1

Speed Characteristics

The speed qualities of a scanner are the first inquiry of the potential customers. Many people consider this as a key factor determining the appeal of the particular model. Yet the most important factor affecting the scan speed is the hardware configuration of your computer. So, choosing a scanner you may just make sure it’s equipped with a high-speed interface, your computer will be doing all the rest.

But back to our tests. When the user calls the scanner’s driver from the control program, the device must perform the pre-scan operation. A typical lamp warm-up time is about 25 seconds on this step. This is actually a standard warm-up time for all scanners with a white mercury-based fluorescent lamp. The warm-up time may increase greatly depending on the task (for example, if you’re scanning transparent originals). You should also keep it in mind that the lamp warm-up operation is performed several times if you’re scanning slides at the optical resolution with Digital ICE technology enabled. In this case the scanning speed goes up even higher.

I measured the time it took to digitize an original at resolutions of 300, 600 and 4800dpi. I didn’t scan an A4 original at the optical resolution since this operation would consume about 3.5GB of disk space as well as an enormous amount of time.


Speeds during originals digitizing

 
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