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Scanning Quality

Scanners with a CCD array differ from CIS-array ones in the depth resolution in the first hand. This feature allows for creating sharp images of centerfolds of thick books and magazines – for the character recognition software to work properly on them. Another application of this property of CCD scanners is making “snapshots” of volumetric items like printed circuit boards, complex relief objects and so on. In fact, you can make a collage of various objects right on the scanner’s glass. As an example, I placed a few felt-tip pens on the bed of the Perfection 4870 and scanned them.


Click to enlarge


This scan confirms the big depth resolution of the device

Of course, such scanning of volumetric objects is of merely academic interest. The EPSON Perfection 4870 is sharpened at digitizing transparent originals, so we should pay much attention to this aspect.

So, this scanner is equipped with an advanced and powerful tool – the hardware and software complex called Digital ICE – and I couldn’t help checking it out. First of all, I checked out the Digital ICE for Films technology. Dust is an annoying thing when you’re scanning slides – it makes you spend much time for post-processing images in an appropriate program.

So I took a Kodak Ektachrome E100S slide for the 120/220 frame. I didn’t specially put dust onto the film surface – there’s enough dust flying around our test lab. Below you can see three fragments of the slide scanned with and without the dust removal technologies. I selected the maximum optical resolution, i.e. 4800dpi. It is in this mode that like under a microscope the slide shows all of its smallest dust motes.


The dust area is marked with red – its fragments are shown below


The slide fragment scanned without dust removal technologies

The first fragment shows what’s here to be seen. Dust is on the surface of the slide like a host of malicious microbes.


The same fragment, but scanned with Dust Removal enabled

Yes, Dust Removal works all right, but it didn’t wipe all the dust away. This software technology left a scarcely visible scar on the image – the trace of interpolation.


That’s the work of Digital ICE for Films. Feel the difference!

The third fragment shows you the result of using Digital ICE for Films. There’s practically no dust left, including the dark specks at the bottom of the fragment. Interpolation is performed at a higher level, using image antialiasing functions. Yes, the result is astonishing, but you should be aware that Digital ICE for Films has certain drawbacks, one of which is incompatibility with some film types. Kodak says only Kodachrome 64 Professional is such, but it doesn’t mean they have tested all existing types of films in their labs. You’ll see below this technology giving an incorrect result.

 
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