Many fine-art photographers still buy drum scanners because the pre-owned scanners are easily available. The second type of scanners are flatbed scanners that have replaced the drum scanners in most of the scanning jobs except for the high ended applications like museum-quality archiving of photographs where scanning of high quality books and magazine advertisements are needed. Drum scanners become advantageous when a very large scanned image is needed due the capability of drum scanners having resolutions up to 24, 000 PPI. The superior resolutions, value structure and colour gradation of the drum scanners make their demand felt in certain sectors. Although the prices of drum scanners have come down but they are still costlier than the flatbed and film scanners. Drum scanners are manufactured only by a very few companies these days. Nevertheless, the drum scanners are still a matter of choice with regard to scanning of films since films can wet-mounted on the drum and due to the exceptional sensitivity of the photomultiplier tubes. However, with coming into existence of the inexpensive flatbed scanners, the use of drum scanners have become obsolete.
The drum scanners could control the aperture and sample size separately. However the output size of the scanned image differed from manufacturers. The original document of maximum 11"x17" size could be mounted on the drum. These scanners derived their name from the clear acrylic cylinder called drum. These scanners scanned the images by using photomultiplier tubes (PMT). The first kind of scanners called drum scanners were first introduced in 1957. Let us discuss these features of scanners in detail. The scanners are most commonly used in modern offices. Digital cameras are based on the concept of reprographic cameras. In the more recent times, digital camera scanners are available as alternatives to the traditional scanners due to their anti-shake, portability and high speed features.
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3D scanners take three dimensional models of objects with full colours. There are also planetary scanners to photo books and documents. Rotary scanners are types of drum scanners for scanning documents at high speed. Old drum scanners used photomultiplier tubes as image sensors, whereas the modern scanners make use of charge coupled devices (CCD) and contact image sensors (CIS). The different types of scanners used in modern offices are desktop or flatbed, hand-held and 3D scanners. The image so scanned is then turned into a digital image by the scanner. The image to be scanned may be text whether typed, printed or handwritten, or a picture, diagram of an object. The purpose of an image scanner is to optically scan an image.
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