Scanner Considerations A scanner is a computer peripheral. You plug it into your computer, insert a slide or negative, push a button, and it converts the image on the film into digital form for use in the computer. There's actually a bit more to it than that, but that's the general concept. When acquiring a scanner, key considerations are scan quality (which is a function of the scanner's optical resolution, dynamic range, bit depth, lens quality and image sensor, among other things), scanning speed, software (capabilities, and ease of use), extra features, and computer connectivity. All of the scanners presented here are capable of producing good scans, or they wouldn't be included. But here are some things to think about: •A scan is a second-generation image. At best, it can be darned near as good as your original slide or negative; but it can't be better. If your original is unsharp or lacking in shadow or highlight detail), no scanner will produce a good scan from it. •While you can make all sorts of corrections to the scanned image using your image-editing software, it's wise to get the image adjusted the best you can before scanning, using the scanner's software. Some scanners come with more-capable software than others. LaserSoft's SilverFast (a third-party item provided with some scanners and available for others as a somewhat pricey separate purchase) is probably the most highly regarded, but scanner-makers' own software is getting better. Check the scanner information on the manufacturer's website (or better still, get an in-store demonstration) to see what a particular scanner/software combination can do. •Optical resolution tells you how big you can print out your scanned images, as touched on in the introduction to this article. Disregard interpolated resolution figures—with interpolation, the scanner just adds extra pixels by making an educated guess as to what they should look like. It's not real resolution, and for photographic purposes is of little value. Some scanners come with LizardTech Genuine Fractals, which is a very good image-size-increasing program, but you can't beat real optical resolution. •Dynamic range figures give you an indication of how well the scanner reproduces the tones in your original slides and negatives. In theory, the higher the dynamic range, the more detail you'll get in shadow and highlight areas. However, different scanner makers have different methods of determining dynamic range. Also, a Dmax figure will be higher than a true dynamic range figure. A film scanner's dynamic range should be at least 3.2 for photographic purposes, and higher is better. Multiple sampling, in which the scanner combines several scans of the image, can also increase shadow and highlight detail, but slows the scanning process considerably. Also, remember that no scanner can give you more detail than your original slide or negative contains. •Bit depth tells you how much information the scanner records for each pixel. A 24-bit scanner can differentiate some 16.7 million shades of color. A 36-bit scanner can differentiate more than 68 billion shades of color. There are even 48-bit scanners among the 10 listed here. Obviously, more bits is "better," but 24 bits is sufficient for most photographic purposes (and some image-editing programs won't provide all features with images with a bit depth higher than 24). •Scanning speeds given my the manufacturers are generally for basic "straight" scans with no "bells & whistles"—no autofocusing or autoexposure, no multi sampling, no dust and scratch removal, etc. Real-world scan times likely will be considerably longer than the maker's specs indicate. •Some scanners come with dust and scratch reduction/removal features (Applied Science Fiction's Digital ICE3 is the best known). This is a very useful asset that can save you hours of retouching after the fact, and we highly recommend it. But be aware that using it slows down the scanning process, and can soften the image slightly. And it doesn't work with conventional silver-image black-and-white films or Kodachrome slides (but it works wonderfully with E-6 slide films and chromogenic B&W films). •Be sure the scanner you get is compatible with your computer. Most scanners are both Mac and Windows compatible these days, but some use FireWire, some USB, some SCSI, and some more than one of these. Make sure your computer will accept the scanner connection, and that you have sufficient processor speed and memory before buying a scanner. (A14-bit-per-channel 4000-dpi scan results in a file size of around 100 MB! But you can also make lower-res scans with the 4000-dpi scanners, when 4000 dpi isn't required.)