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Tuesday, June 19, 2007

Large-Format Scanning

Discover the alternatives for producing your own scans in-house



Large-Format Scanning If you shoot or have an extensive archive of large-format negatives or transparencies, the process of converting them into digital files can be costly. When done at a service bureau, each drum scan can run from $30 to $400. Depending on the number of scans you need, this can become prohibitively expensive, which is why many photographers consider the use of scanners to produce digital files in-house.

Deciding whether to invest in a CCD-based scanner or a drum scanner is challenging. While each has its own advantages, there's a significant difference in price, ease of use and quality. In addition to price, determining the right choice is largely dependent on expected frequency of use and the quality demands for your output.

PMT Vs. CCD

Scanner types are based on two technologies—those that utilize a photo-multiplier tube (PMT) or a charge-coupled device (CCD). At the heart of any drum scanner is a PMT, a light-sensitive vacuum tube that provides a wide dynamic range due to its high light sensitivity. Flatbed and “virtual” drum scanners use CCD technology, similar to the sensors that exist in digital still and video cameras. Because of the lower cost of production, CCDs allow for more affordable scanning devices while maintaining a high level of quality.

Each scanner type offers distinct advantages. Although it's based on the older technology, a drum scanner still is considered the gold standard. Offering resolutions as high as 11,000 dpi and more, it boasts a wide dynamic range with minimal noise. Drum scanners deliver digital files that provide quality enlargements of more than 800%. When the scanner is properly used, the resulting files reveal high levels of detail as well as render subtle gradations of tone and color, qualities that hold up even with big enlargements.

As CCD-based scanners have increased in resolution to 8000 dpi and higher, they have entered a territory once dominated only by drum scanners. Their ease of use combined with a comparatively lower price point make such scanners both affordable and more accessible to photographers. Yet resolution and pricing alone don't tell the complete story.

Virtual Drum Scans

The Hasselblad and Imacon Flextight scanners (since their merger, different models of Flextight scanners are distributed under the Hasselblad and Imacon names in the United States) offer a sort of hybrid between a flatbed and a drum scanner. Promoted as a virtual drum scanner, the Flextight scanners combine high-end CCD technology with a glass-free mounting system that curves the film, resulting in the flat mounting of the transparency or negative. The Imacon Flextight 848 and 949 models offer resolutions as high as 4000 dpi for medium-format film (645) and 8000 dpi for 35mm. The Flextight's glass-free design eliminates unwanted reflections and distortions, such as Newton rings, which can occur when using flatbed scanners.

In addition to providing higher resolutions than many consumer flatbed scanners offer, virtual drum scanners also feature a more efficient means for mounting and properly aligning film. Bowed and curved film can be challenging using a flatbed scanner, but the Flextight system eliminates such problems.



 

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