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Alaska Business License # 712765
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Graphics scanners are the optical imaging device of choice for converting documents, photographic prints, frames of film, and illustrations drawn or printed on paper into a digital image. The digital image a scanner makes is stored as a graphics file on a computer media storage device such as a hard drive or floppy drive. This file is retrievable at anytime to print or to view on a monitor. The scanner's resolution, color depth value, and optical density determine the quality and appearance of the copied digital image it creates. Current professional quality scanners are capable of matching or exceeding the detail and image quality provided by high quality film. The secret of effective scanning is to have a simple understanding of the mechanisms and electrical components of a scanner and to learn how to adjust color depth, resolution, contrast, brightness and other values to obtain a digital image and save it using the file format and size that does what you need it to do. Scanning images or documents at the highest color depth and resolution just because you can will produce huge files that did nothing relevant to making improved quality and appearance of the scanned image. The scanner’s sensor is a Charged-Coupled Device (CCD) consisting of 3 RGB cells per pixel arranged in a single row of pixels across the width of the scanning area. This row of pixels then copies portions of the image as stepping motor moves the CCD in small precise steps along the length of the scanning area. Mirrors and a wide angle lens focus the image onto the small CCD sensor because it is only a couple of inches long while the width the scanning area of a scanner is typically 8.5 inches or more. The capability of the CDD determines the highest optical resolution a scanner can provide and it is the first and lower dpi number of the maximum hardware resolution the scanner is capable of providing. The precision and number of motor steps determine the number of pixel line scans used to sample the image being copied and this is the second and higher dpi number of the maximum hardware resolution a scanner is capable of providing. Consequently, a maximum hardware resolution of 2400 x 4800dpi tells you the maximum optical resolution the scanner is capable of is 2400 dpi and that 4800 one-pixel scan lines per inch is sampled from the reduced image the lens and mirrors project onto the CCD cell. Digital images must have square resolution and this is part of the relevance of a scanner’s maximum interpolated resolution. What this means is firmware (software permanently loaded on computer chips) manipulated optical resolution and the number of one-pixel line scans to ensure horizontal and vertical resolutions are equal (square). It also means the firmware has the ability to calculate (guess) a resolution higher than the optical resolution is capable of providing. This is a very oversimplified explanation, what is important to know is, scanning at resolutions higher than the maximum optical resolution of the scanner provides no added detail from the original picture, just a larger picture. Things are scanned for several end uses and effect the choice of resolution, sizing, color depth, and other values used. For instance a 300 dpi resolution provides good results for scanning a picture to put on a web page, but if you are scanning to enlarge and print it, then 1200dpi is the better resolution value to use. A scanned 8 inch by 10 inch color photograph scanned using the highest value resolution available can easily be 50MB in size. Bit depth, bit density, and dynamic range of a scanner refer to the capability of the CDD sensor and firmware to detect brightness, shade, tone, color, and detail. These specifications lack easy explanation, but bit depth determines the number of colors or shades of grey the scanner can possibly distinguish at one time. Dynamic range is relevant to how much shadow detail is captured from a source image. Dynamic range is not very critical for copying photographic prints as they have limited dynamic range, however, this is a critical specification when copying images from positive film (slides) and images from film negatives because these image sources have extensive dynamic range capabilities. A scanner’s specifications are more pertinent to the scanning of slides and photographs than it is for scanning documents. Slides and photographic prints are scanned to preserve the images on them for future printing or for archival purposes to prevent permanent loss should the original source image be lost or severely damaged. Slides and photographic prints are also scanned to put a copy of the source image into a multimedia slide show on DVD or to post for display on the internet. The purpose for scanning determines the digital resolution and image size needed which also determines the image file size you will end up with. Higher resolution and 100% image size output is advantageous for repairing, restoring, or editing a picture and also if the scanning purpose is for archiving or printing the picture. Lower resolution and less than 100% image size output is desirable if the scanning purpose is to use the image in a multimedia slide show or for posting and displaying on the internet. A scanning resolution of 300dpi (actually 300 x 300 dpi because digital images have square resolution) sufficiently reproduce all the detail available from a source color photographic print. But 300 dpi is often not sufficient to capture all the detail available from a source B&W photographic print, film negative frame, or an original positive film (slide). For the purposes repairing, restoring, or editing a damaged or deteriorated picture it is very desirable to use either the maximum optical or hardware resolution the scanner is capable of. Currently available high-end quality consumer model scanners are capable of digitally reproducing the detail and image quality from the best high quality film image, but your scanner results will also depend upon your own skill. Digital images not only preserve family history, but also make it easier to share it with others. More importantly digital images integrate into attractive interesting presentations such as narrated slide shows on DVD-video or in a family history book. CY Technical and Professional Services can transfer your film, photograph, and paper memories into keepsake memories you can easily replicate exactly and give to all your children and grandchildren. |
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