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An acquired taste by Tim Daly, from Ag29 |
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Density: In addition to capturing the range of detail across a film or print original, the inherent density of an original needs consideration too. Density has become a desktop term taken from both the professional lab and pre-press bureau world. Essentially it describes the range of difference between the most dense area (Dmax) and the least dense area (Dmin) on both reflective photographic originals, ie prints, or transparent originals. In practice the measurement of a dynamic range is arrived at by subtracting the Dmin from the Dmax, with a typical transparency material having a Dmax of 3.3 and a Dmin of 0.3, resulting in a density range of 3.0D. Print materials have a much more compressed density range, set somewhere between 2.0D and 1.7D. This complex theoretical background may seem unimportant when it comes to making great images, but its use is crucial when applied to the purchase of a good film scanner for your workstation. The inherent difficulties in capturing a faithful scan from a colour transparency centre on the lack of light transmitted through the densest shadow areas, which can prove impossible for a budget film scanner with a density range less than 3.0D to detect. Better or repro-quality scanners, which have a dynamic range of 3.0D and over, can deal with these difficult tasks and also other hidden gems in your library such as overexposed or overdeveloped black and white negatives, ultra-dense lith film and even oddities like infra-red. Density is much less of a problem if you only shoot and scan colour negative, chromogenic black and white and low contrast black and white negatives. Resolution: Resolution is a term that can also be applied to colour depth, but in this instance refers to the number of pixels the scanner can create from an inch of picture information. Flatbeds are described by two measurements e.g. 600 x 1200ppi, or width x length. With many devices now producing up to 2400 pixels per inch, searching for good quality its much less of an issue than with film scanners. With film originals being inherently smaller than prints, film scanner sensors are designed and built with much higher resolutions than flatbeds. Typically starting at around 2400ppi and increasing to around 4000ppi, the former creates files of around 20-30Mb and the latter produces a gargantuan 70Mb+ of information; higher price devices enable you to output on a larger scale. For those interested in scanning medium format film and the many size variations within it, it is important to check that the maximum resolution of these kind of film scanners is maintained throughout the range and not halved or interpolated. Next Page >> |
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• With black and white negatives, actual film exposure can present difficulties. In this example a thin negative was scanned as follows: top left: no adjustment; top right: Auto ‘exposure’; bottom left: modified with the crude brightness slider; bottom right: same as bottom left but in the opposite direction. © Tim Daly Page 3 0f 6 |
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