Slide scanners: Getting colors right
- By Patrick Marshall
- May 20, 2002
How important is it that you get the colors right in images in your print publication or on your Web site?
That's not a rhetorical question. Of course you want everything to be perfect. But if the faces of people in a photograph are a little too pink or if the sky is just a tad too blue, most people will never notice the difference. So why spend the extra dollars and effort to achieve high fidelity?
In some situations, getting the colors right does matter. For example, when publishing brochures for the general public, or for higher-ups, you want to make a good impression. In such cases, sending your film to a one-hour developer and then scanning the photos on a flatbed scanner is not likely to produce the desired results.
In fact, even before you click the shutter, you're making choices that will affect the way the resulting image will print. The type of film you use — assuming you're using a film camera rather than a digital one — and the exposure setting will both have an impact. And once you click the shutter, each version of the captured image can result in further changes.
If you take your film to a lab and get prints back, the colors will almost certainly have shifted from the original image. And if you then scan those prints into the computer, you're going to introduce more color changes.
Even more shifts occur in printing. All printers — even professional printing presses — have limitations in the way they reproduce color. Desktop inkjet and color laser printers are so limited in the range of colors they can print that they actually substitute colors. By the time you actually print the image, in other words, it may be quite a bit different from the original.
The two most critical stages in the process are when the image is converted to a digital format and when it is returned to a nondigital format during printing. The best way to ensure accurate colors in the conversion to a digital format is to employ a slide or film scanner.
Slides and color negatives retain more color data than printed photos, and scanning directly from a slide to create a digital image removes a step from the conversion process — that of printing the image on photo paper before scanning it on a flatbed scanner.
For this review, we took a look at two of the most popular desktop slide scanners. These are not top-of-the-line scanners; you can spend thousands of dollars on drum scanners like those used by professional service bureaus. But we were impressed with the results professionals and consumers can achieve for less than $1,500.
Nikon USA's Super Coolscan 4000 ED represents the state of the art in desktop film scanning, delivering crisp and color-accurate scans without the need for the frequent post-scan corrections required by other scanners. The Minolta Co. Ltd. Dimage Scan Elite II is a good fit for those who want a professional-quality desktop scanning device at a bargain price.
Nikon Super Coolscan: Worth the Extra Dollars
If you really need to get the image right without fussing with software adjustments, you'll want to spend the extra dollars for the Super Coolscan 4000 ED.
With the ability to scan at up to 4,000 dots per inch, the Super Coolscan 4000 ED delivers the highest resolution of any scanner in its class. If you're only planning to print at 600 dpi or 1,200 dpi, being able to scan at 4,000 dpi may seem like overkill. But if you need to zoom in and capture just a portion of that slide, you will be grateful for the extra resolution.
The Coolscan can scan both mounted slides and unmounted film, and it can handle both color positives and negatives. The device comes with three film holders — one for mounted slides, one for strips of film and a clamshell device for scanning short pieces or damaged film.
Nikon also offers additional holders, including one that accommodates up to 40 frames of uncut film and one that can hold up to 50 mounted slides. These optional holders are especially handy if you plan to take advantage of Coolscan's powerful batch processing capabilities. What's more, you can swap holders in and out without shutting down the unit.
We were very impressed with the Coolscan 4000 ED's color reproduction. The device is capable of converting the analog data acquired during scanning to digital data at 14 bits per color channel. And unlike many scanners, the Coolscan will save all 14 bits instead of just the "best" eight bits. The trade-off for that extra data is, of course, larger files. A slide scanned at 4,000 dpi with 14-bit color results in a 50M file.
Nearly all of our scans produced results that required no color correction. Some slides required an adjustment of about 20 percent in brightness, but you can set the software to make that adjustment automatically if desired.
The sharpness and color fidelity of the Coolscan 4000 ED likely result from a couple of unusual features in the unit's design. First, while most scanners use fluorescent light sources and color filters, the Nikon line employs red, green and blue LEDs. That strategy avoids the inevitable fading of color filters and takes advantage of the shorter wavelength of LEDs to enhance resolution. Nikon also touts its extra-low dispersion optical glass as enabling clearer, truer scans.
We found the unit's Microsoft Corp. Windows-based software — Nikon Scan — to be relatively easy to use, though not quite as friendly as the software that comes with the Minolta Dimage Scan Elite II. Once we learned our way around the software, however, we found it simple to perform most scanning chores, such as previewing and changing resolutions or file formats. And even such potentially daunting tasks as setting up batch processing can be achieved without too much trouble.
If you have degraded or faded slides, you'll also appreciate the integrated suite of tools from Applied Science Fiction Inc.:
n Digital Image Correction and Enhancement (Digital ICE), which removes scratches, fingerprints and other defects from scans. The utility works surprisingly well, though we did notice that it slightly detracts from the sharpness of the image.
n Digital Reconstruction of Color (Digital ROC), which restores vibrant colors to scans from faded color negatives.
n Digital Grain Equalization and Management (Digital GEM), which reduces the effects of film grain — especially important when resolutions rise above 2,800 dpi.
We thought the scan-correction utilities were excellent. Employing them adds significantly to processing times, but if you have a batch of film that needs such corrections, it's much quicker to employ the utilities than to make the corrections image-by-image in a program such as Adobe Systems Inc.'s Photoshop.
Nikon offers a number of other correction utilities and capabilities. In addition to the company's own Color Management System — which enables you to bring images into Photoshop using any of 10 popular color workspaces — the Coolscan 4000 ED supports ICM for Windows and ColorSync for Apple Computer Inc.'s Macintosh platform to help ensure consistent colors when printing and displaying.
All of this processing, of course, takes time. A full scan takes about 38 seconds per slide, but that doesn't count the post-scan processing. Even without employing the special correction utilities, post-scan processing adds another 60 seconds or so to each scan. Fortunately, the Coolscan 4000 ED cuts down somewhat on processing time by communicating with the computer via a FireWire interface. An interface card is included with the scanner.
Keep in mind, however, that the Coolscan 4000 ED is not the top of Nikon's line. The Coolscan 8000 ED, which carries a street price of more than $2,000, offers the same resolution as the 4000 ED, but it can handle a wider variety of film formats, including 16mm and microscope film.
Minolta Dimage Scan Elite II: Quality on a Tight Budget
Make no mistake, the Minolta Dimage Scan Elite II is a quality slide scanner. Nevertheless, the main reason to choose it is if your budget is tight. For all of its virtues, the Scan Elite II does not match the Nikon unit's resolution or color fidelity.
The Scan Elite II offers a top resolution of 2,820 dpi and a surprisingly high — 16 bits per color channel — analog-to-digital color conversion. The scans are sharp, but we also found them to be dark and to have significant color shifts. Depending on the value ranges in your slides, you can change and save scanning characteristics to adjust scans automatically. Otherwise, you'll have to make post-scan adjustments using the software, which is a time-consuming process.
We also encountered a few snags with the Scan Elite II's slide holder. Slides must be inserted into a slide holder, which is then inserted into the front of the device until the holder is "grabbed." From that point, the device takes over, moving the holder over the scanning lamps.
Unfortunately, the slide holder does not offer good tactile feedback, so we found it difficult to tell when we had inserted the holder to the proper point. Also, the holder often got stuck during scans and needed to be pushed or pulled slightly to get it moving again.
The slide holder can accommodate up to four mounted slides, and Minolta also includes a holder for up to six frames of unmounted film.
We found the Scan Elite II's software scanning interface somewhat easier to use than Nikon's. And, like the Nikon Coolscan series, the Minolta unit includes the Digital ICE, ROC and GEM correction utilities.
The Scan Elite II also stands out for its manual focusing options. Fortunately, in most cases, the device's autofocus will be adequate.
But if getting just a bit more sharpness out of a scan is important, you'll find that manually focusing produces slightly better results, especially with slides of marginal quality. Manual focusing can be tedious, especially given the amount of time required for scans and prescans, but the Scan Elite II software offers a "live feedback" feature that makes the job much easier.
The Scan Elite II supports both USB and FireWire connections, but we strongly recommend using the latter whenever possible.
Although the Scan Elite II may not deliver 4,000 dpi resolution and the out-of-the-box color fidelity that Nikon's Super Coolscan 4000 ED offers, it is a quality scanner that offers surprising value for less than $700.