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Save Those Old Negatives and Slides
Most people have some slides or negatives that they need to digitize. Whether it is an old family album or entire collection of images shot on film, those images can be preserved and reproduced digitally. The key is to choose the correct type of film scanner for the job. Not all scanners are created the same or used for the same purpose. Basically, there are four options in film scanning using a scanning service to scan film, having a drum scan, using a flatbed scanner or using a dedicated film scanner.
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How Scanners Work
The two main types of sensors used in scanners are Charged Coupled Devices (CCDs) and Photo Multiplier Tubes (PMTs). Scanner sensors convert light into electronic information, i.e. pixels that make a digital image. PMT sensors have a higher density range and record more information in the shadows and highlights than CCD can record. Drum Scanners are PMT devices and flatbed and dedicated film scanners use CCD sensors.
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Resolution and Dynamic Range
Resolution is determined by the number of ppi (pixels per inch). This is the amount of pixels a CCD reads during the scan. A large resolution allows the scanned imaged to be enlarged and still maintain sharpness and good quality in the print. PMTs do this better than CCDs, but unless the image is going to be enlarged to 20x30" or larger there are many good options with CCD scanners.
Dynamic range is the amount of recordable colors from black to pure white. The larger dynamic range the more detail in the shadows and highlights. This also means less noise and more sharp detail in the image.
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Many professional scanning labs can scan large volumes of negatives and slides with short turn-around times. This is probably the easiest solution, but not the most economical.
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Drum scans are the highest quality scans. They have the highest resolution and the least electronic noise in the scanned image. Most advertising agencies use drum scans because of the high quality and high resolution. Many ads are printed large or may be in the future. They also have the budget to pay for the expensive price of drum scans. Drum scans are slow. They take a long time to scan one image.
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Flatbed scanners use CCD sensors. Due to the nature of the sensor and the design of the flatbed scanners, they are limited on resolutions sizes. CCD sensors read one horizontal line at one time. If the scanner is rated at 1200x2400 dpi, the CCD will read 1200 samples per inch. The first number (1200) is the optical rating of the scanner and the second number is the possible positioning of the carriage stepping motor. This motor moves in precise steps. In this case, the motor would move at 1/2400 inch vertically for each pulse of the carriage motor.
Flatbeds do not focus on the film plane and have difficulty differentiating between pixels and dust. Another downside is they have trouble distinguishing between two light points. This means less detail in the shadows and highlights. The optical resolution of flatbed scanners is too low for professional results. These are multi-functional devices with trade offs in quality for varied functions. Two exceptional flatbed scanners with extremely high optical resolutions that can produce professional results are the CanoScan 8800F (4800x9600dpi) and the Epson Perfection V750-M Pro (12,800x12,800 Interpolated) these two will produce higher quality film scans.
If the negatives to be scanned are for use on the Web or viewed on a computer only, a flatbed scanner will produce an image of sufficient quality. Otherwise, for large images and results that are more professional a dedicated film scanner should be used.
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Dedicated Film Scanner
Dedicated film scanners also use CCD sensors. The difference is that they use transmissive light. This is light passing through the negative as opposed to the reflective light of a flatbed scanner. Dedicated scanners are faster and produce the highest fidelity image reproduction. These scanners have a higher bit depth, which means more gradations of color. They also have many software and firmware options. For large film libraries, using a dedicated film scanner will speed up the process and produce professional quality results.