A Buyer's Guide to Film Scanners
Film scanners are made for the sole and express purpose of scanning film directly into your computer. Unlike their flatbed counterparts, which may be able to handle media of various sizes and thicknesses and can even scan film if a transparency adapter is installed, film scanners scan only one thing: film. But because the image to be scanned is taken directly from the original material - from the film, and not from a print - film scanners allow more direct control over image elements such as cropping and aspect ratio. In addition, film has more detail and dynamic range compared to prints - which invariably lose tonal range and color data during the printmaking process. These are real concerns to photographers and graphic artists, who rely on original slides and film - and film scanners - to ensure the integrity of scanned images in professional and commercial applications. So, if your work relies on scanning negatives, slides, and other types of film, a film scanner is the right choice for you. This buying guide tackles some of the more important things that you need to know when looking for a film scanner.
Style and Type Some flatbed scanners include either an external or built-in transparency adapter that is used to scan film. Other flatbeds are of a dual-bed design; i.e., with one bed - the glass flatbed part of the scanner -for scanning prints; and another bed - a transparency bay that looks like a pull-out drawer - for scanning film. If you intend to scan only the occasional slide or stray piece of film, and don't mind the lower resolution as well, a flatbed scanner that can accommodate film may well serve your purpose. Be aware, however, that the resulting film scans will not be suitable for commercial or professional use. To obtain the best results, nothing less than a dedicated film scanner will do.
Bit Depth
A scanner's bit depth determines the number of bits captured per pixel, which is related to the number of possible colors. The higher the bit depth is, the greater the number of colors that can be shown. Bit depth for film scanners on the market today can be 30-bits, 36-bits, 42-bits, or 48-bits. Always aim for higher bit depth when possible, as this allows the scanner to work with and retain a greater amount of color information. A 48-bit scanner, for instance, produces 65,536 levels or shades of color per R,G,B (red, green, blue) channel, resulting in a mind-blowing possible combination of about 250 trillion colors. In contrast, a 36-bit scanner produces 4,096 levels of information, or a paltry 68.7 billion colors.
Resolution
For scanners, the optical, or "true", resolution is what matters, as this is the actual number of pixels being read by the scanner's optics. Film scanners have much higher resolution figures compared to flatbeds, with optical resolution in film scanners ranging from 2700 dpi to 5400 dpi, and 4000 dpi being the most common. The high resolution in film scanners allows you to enlarge small images, creating enough pixels in the process to print in full-page size.
For instance, a full-frame 35mm color negative scanned at 2400 dpi will result in a size of about 3400 x 2200 pixels. If this 2400-dpi image is printed at 300 dpi, the resulting printed image will be 8 times larger than the original film size (2400/300=8). In actual terms, this means that your original 1.4 x 0.9-inch film (36 x 24 mm) can be increased by 8 times to 11.2 x 7.2 inches when printed at 300 dpi - without any loss of image clarity or detail. A word of caution: Because film scanners can scan in such high resolutions, file sizes can be big. Scanning the 35mm negative at 2400 dpi in the example just cited will result in a file size of 22 megabytes.
Film Formats
Most film scanners work with 35mm film. Some can scan APS film, but an optional APS adapter is needed to batch scan the full APS roll. Other film scanners, such as the Microtek ArtixScan 120tf, can scan medium format film as well, ranging from 6x6cm to 6x17cm panoramic. Check to see what types of film holders are provided with the film scanner; most models will include a 35mm slide holder as well as a 35mm filmstrip holder. A few models offer optional autofeeders that accommodate 50 mounted slides to allow efficient batch scanning of film.
Interface
The hardware interface of your film scanner will determine how long it takes to transfer digital data to a computer for processing. Together with the actual operational speed of the scanner, the hardware interface plays an important part in determining scan speed. Most older film scanners have SCSI ports; the newer film scanners feature FireWire or USB (Hi-Speed or USB 1.1) interfaces. Models with either USB or FireWire interface are hot swappable - which means the scanners can be plugged or unplugged from other devices to which they are connected without having to turn the scanners off and on.
Dynamic Range
The dynamic range of a scanner measures how well it can capture the tonal range of an image, ranging from the brightest highlights to the darkest shadows. Dynamic range is a more important spec in film scanners than it is for flatbeds, because film and other transparent media have a broader range of tones compared to photos or prints - something that film scanners are perfectly equipped to capture and show. Dynamic range is measured on a scale from 0.0 (perfect white) to 4.0 (perfect black), and the single number associated with a scanner indicates how much of that range it can tell apart. The minimum and maximum density values that can be captured by a scanner are called Dmin and Dmax, respectively. If a scanner's Dmin was 0.2 and its Dmax was 4.2, then its dynamic range would be 4.0. The dynamic range of film scanners are usually advertised by their manufacturers as falling somewhere between 4.0 and 4.6, but these are intrinsically difficult figures to prove or validate, and a model claiming a higher number may not necessarily have better results to show, mainly because of variances in testing and determining the figure. A more practical way of assessing would be to visually check how shadows and highlights are reproduced by the scanner and then compare the results to the original image or to how other scanners reproduce those same tonal colors.
Dust-and-Scratch Removal, Film Repair
Software provided with film scanners can be specialized and varied. Like flatbeds, film scanners will include their own driver or scanning software, as well as bundle an image-editing program - such as Adobe Photoshop - into which scanned images are delivered and placed. In addition, higher-end film scanners may include a color calibration and ICC profiler program, which ensures consistent color by creating a color profile specific to the film scanner. With the ICC profiler program, an image - known as an IT8 target and containing industry-standard color values - is scanned, and then compared to values that the scanner actually recorded. The differences are then translated into a compensation scheme to even out color variations, so that accurate color results can be produced in the future.
Dust and scratches on film can present a big challenge for film scanners, as imperfections can take on gigantic proportions when the film is scanned at the scanner's very high resolution. Film can also be damaged through improper handling, and what appears to the naked eye as a tiny scratch may render the image on a film practically useless. For this reason, a number of film-repair technologies have been developed to remove imperfections, allowing an image to be reconstructed and printed flawlessly, as though it came from a pristine original. These film-repair technologies may be implemented either through software alone, such as the dust-and-scratch removal feature from the SilverFast program by LaserSoft Imaging; or through a combination of hardware and software, as is the case with the DIGITAL ICE technology built-into some models.
Other technologies
Depending on the model, film scanners may incorporate proprietary technologies unique and exclusive to their manufacturer. Such technologies may include an auto-focus mechanism to ensure perfect image capture, a patented feeder mechanism, or specially designed holders for making film stay flat. These features may make a real difference in improving the quality of your scanning or streamlining your workflow.
Microtek Lab Inc. is a consumer electronics company focused on scanners, plasma and lcd televisions, digital projectors, lcd monitors, digital cameras, home theatre equipment, and accessories. You can view their online store at http://www.store.microtek.com Use of this article is permitted provided that the article is used in its entirety.
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