Qualities of Good Digital Scanners
A digital scanner helps preserve images and text documents for archival purposes. A mid-range digital scanner captures a sharp, detailed image with true colors. Good scanners offer easy to use hardware and software for a streamlined process. Important factors for rating a scanner include the desired image quality for a high-resolution file and the ability to scan different types and sizes of materials.
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Scanner Resolution
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Scanner resolution measures in pixels per inch, referring to the digital image. Mid-range scanners contain scanning heads with charge coupled device light-sensors, each with a true optical resolution of 600 ppi. Optical resolution refers to the scanning head’s sampling rate or number of light-sensitive elements. Optical resolution is different from the interpolated resolution. Interpolated resolution includes a guess value of additional pixels between the original scanned pixels for a larger file resolution without the original file’s sharpness and true colors. For example, the CanoScan LiDE 700F film and negative scanner features a maximum optical resolution of 9600 by 9600 dpi and an interpolated resolution of 19,200 by 19,200 dpi.
Density Range
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Density range or dynamic range refers to the scanner’s ability to record tonal qualities. Density range uses a scale of 0.0 to 4.0: a dynamic range of 0.0 refers to perfect white; between 0.0 and 4.0 refers to graduated levels of gray; and 4.0 refers to perfect black. For example, a mid-range scanner has a dynamic range of 2.8 to 3.2. A scanner for color prints should have a density range of at least 2.7. For color slides or transparencies, the scanner’s dynamic range should rate at least 3.2.
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Types of Scanners
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A good digital scanner suits the type of materials being scanned. For example, a flatbed scanner contains a glass platen that accommodates prints, bound pages, text documents, business cards and other flat items that fit on the scanning area. The hinged door or flap helps minimize unwanted light from interfering with the scan. An automatic document feeder scans longer documents and multiple pages that feed unattended. Photo scanners provide higher quality scans of prints of limited size. Photo scanners offer the advantages of increased resolution and dynamic range. Film or negative scanners transmit light through the image for large files with increased dynamic range and resolution. Some flatbed scanners come with a film adapter.
User-Friendly Software and Panel Controls
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A good digital scanner includes bundled software that allows tweaking before the scan. For example, adjusting the brightness, contrast and image rotation helps optimize the initial scan that creates a high-resolution file. The user needs to feel confident applying the scanner’s software tools. The scanner’s software minimizes the time and effort for adjusting files with a computer’s graphics editing software. The scanner’s exterior should include panel controls for the scan button, as well as copy, PDF and email buttons. These push buttons automate the scanning without the need to open the software tools.
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References
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