By Ibarionex R. Perello – DigitalPhotoPro.com
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.
Achieving corner-to-corner sharpness is important when scanning your images, and the Flextight system ensures this by providing adjustable focal lengths inside the housing, hence the height of the unit, in addition to utilizing a unique magnetic film holder. Achieved automatically based on the film format being scanned, the optics perform as a long focal length, resulting in less distortion, especially toward the edges of the frame.
While CCDs can be prone to signal noise, particularly when scanning dense transparencies, the Flextight scanners reduce noise by housing the power source outside of the scanner housing and by using a cold cathode tube, which produces minimal infrared waves and, thus, heat. This is particularly important when scanning low-key images where noise can become quickly evident in areas of shadow.
Many photographers often see this system as an excellent compromise between a flatbed and a drum scanner.
A high-end flatbed scanner also can produce quality digital files that suit many professional needs. For the most discerning eyes and maximum flexibility down the road, consider investing in higher-end units, which range in price from $2,000 up to $8,000.
Flatbed scanners, such as those manufactured under the names of Aztek, Cezanne, Creo, Epson and Heidelberg, all follow a similar design. The digital file is produced by placing the film between a glass plate and a light-emitting adapter. The light passes through the film, onto the CCD and then is converted by an analog-to-digital converter into a digital file. With such scanners, it’s extremely important to keep the glass clean to minimize the appearance of dust and dirt in the scan. Many flatbed scanners include software that automatically detects and removes dust and scratches.
Some high-end scanners share the same resolution as drum scanners, but it doesn’t automatically equate to similar quality. This is because CCDs can produce greater signal noise, which is particularly evident in the shadow areas. Although some scanner manufacturers advertise a dynamic range higher than the theoretical maximum of 4.0, they may achieve their figures by increasing or amplifying the gain, which results in greater noise.
For many, the image quality and enlargement sizes that these scanners deliver may satisfy both a studio’s quality demands and budget. With a well-exposed piece of film with moderate magnification, it can be difficult to tell the difference between a scan produced by a high-end flatbed scanner and a drum scanner.
Providing resolutions as high as 11,000 dpi and more, drum scanners produce digital files that can lead to exceptional enlargements of more than 800%, in addition to offering a wide dynamic range with minimal noise. Achieving this high image quality requires a precise and consistent workflow.
Unlike other scanners, a drum scanner involves the wet mounting of film to the translucent drum. Using special oil that bears the same refractive index as film, the film is taped to the drum, which then rotates at high speeds. A laser hits that film and the concentrated light is picked up by the PMT. It’s the PMT’s incredible sensitivity to light that provides the superior image quality.
Prices range from $5,000 to as high as $45,000 and more. While the higher price point reflects an increase in image quality, it doesn’t reflect the time involved in learning to make the best use of these units. Considering the expertise required to get the most from a drum scanner, you’re probably better served by going to a lab with a reputation for excellent scans, rather than spending the money on a unit for your studio. By doing so, you’ll be leaving drum scans in the hands of a qualified technician and you’ll get the best results.
Aztek (800) GRAPH-55 www.aztek.com
Creo (800) 929-9209 www.creo.com
Epson (800) GO-EPSON www.epson.com
Hasselblad/Imacon (Flextight) (973) 227-7320 www.hasselbladusa.com
Heidelberg (888) 472-9655 www.us.heidelberg.com
Hewlett-Packard (800) 752-0900 www.hp.com
Screen USA (Cezanne) (847) 870-740 www.screenusa.com