Scanned heat

Introduction

High-end scanning requirements are quite different to those at the consumer end of the market (Macworld, November 2002). Professional photographers and graphics folk need to be able to scan transparencies and reflective artwork, manage colour, resolution and other image-quality issues, and will often need to batch-scan work. Although image quality is important, so is the scanning software that’s used. Professional scanners may appear similar in appearance to many of their consumer counterparts, but are a world apart in terms of what they offer. The good news is that, in the pro-scanner market, ease of use has improved markedly over the years. The bad news is that product choice has shrunk along with the number of players in the market. The professional-scanner market was once vibrant, with manufacturers involved in an arms race of features and specifications. Now, though, scanning technology is so mature that the battle to increase specifications is no longer being waged: innovations are few and far between. One of the biggest indicators of the stagnant nature of the market is how many of the scanners in this round-up featured in last year’s. Even more worryingly, a couple were even in the same feature two years ago. Perversely, this market stagnation has occurred in the face of buoyant demand for high-end scanners. Scanning hardware may be standing still, but scanning software continues to improve – in terms of both functionality and useability. In the past, scanner software was aimed at colour experts boasting years of experience in the field. Current software, though, is much easier to get to grips with, and often has highly intelligent automated features. Making your mind up
There are a number of definitive ways of measuring a scanner’s worth. Resolution A scanner’s resolution allows you to measure how much an original image can be enlarged with no degradation in quality – something that’s especially important for scanning transparencies. Remember, resolution is a measure of size, not quality. More pixels are not necessarily better pixels – a scanner’s high-resolution specification is an indication more of its flexibility. Here’s how it works. Most images are scanned at 300dpi: one needs scan at a higher resolution only if planning to enlarge the image. Being able to enlarge a 35mm slide to 10 times its original size may be extremely handy, but only if that capability is going to be used. Super-high resolutions cost money, and if you use it rarely then the investment is an uneconomic one. Density range This is the measurement of the range of shades that the scanner can see. If a scanner has a low density range, images will lose detail in areas of highlight and shadow. Capturing a large range of image density allows for better control of the image once the scan is completed. A high density range means that poorly lit or shot images – with areas that are bleached or overly dark – can later be remedied, because the detail is recorded, even if it isn’t visible. Bit depth This is the measure of how many colours are visible to the scanner. A bit is the smallest unit of information that a computer understands. It has two possible states: it can be on or it can be off. All computer information is handled in this way. A black-&-white line drawing, for example, has one bit per pixel. When on, the pixel is white, and when off, it’s black. Each pixel has a bit depth of one and a colour depth of two. Low-end scanners tend to be 24-bit models, which means they offer 8 bits per channel, with there being three channels – red, green and blue (RGB). Mid-range models – and some models at the entry-level end of high end – offer around 12 bits per channel (36 bits). The ArtixScan 2020 apart, professional-class scanners are invariably 42-bit or 48-bit models. Why bother with bit depth?
Scanning software bundled with those scanners offering a colour depth of more than 24 bits usually allows the user to save scans as both 8-bit and 16-bit files. Although this may sound like a difference of just 8 bits, it couldn’t be further from the truth. In a 24-bit file, each of the three 8-bit channels contains 256 (2 to the power of 8) shades of grey describing each pixel in each channel. Combining the three channels gives a file containing 16,777,216 colours (256x256x256). In a 48-bit file, each of the three channels contain 16 bits per pixel, or 65,536 shades of grey, giving 281,474,976,710,656 colours. Only 48-bit scanners offer “true” 16-bit images – meaning that 16-bit files really do contain 16 bits per channel. This is not the case with sub-48-bit models. For example, although a 36-bit scanner may allow you to save in 16-bit format, it’s incapable of offering more than 12 bits per channel, or a ‘miserly’ 68,719,476,736 colours. Who needs 16-bit files?
In short, anyone planning to import scans into an image editor that can handle 16-bit images, such as Adobe Photoshop 7.0 (reviewed in Macworld June 2002), Binuscan’s PhotoRetouch Pro (April 2002) or Asiva Photo (October 2002). But beware: the way 8-bit images behave when edited is markedly different to 16-bit files. During the 8-bit image-editing process many colours and tonal values can be lost – and the more changes made the greater the degradation; maybe to the point of pixelation, posterization, or banding, especially in subtle areas of highlight and shadow. Used injudiciously, Photoshop’s Adjust menus (Levels, Desaturate, Curves, Color Balance, Contrast/Brightness, Hue/Saturation) are as likely to destroy an image as improve it. This is why I prefer PhotoRetouch Pro’s powerful one-step adjust feature, Auto Process RECO. Photoshop’s Adjustment Layers may allow you to edit an image without altering the original file’s content, but they do invite incessant tweaking and fiddling. Things are different with 16-bit files – especially true 16-bit files – because the editing process is non-destructive: the image contains so much damn information that even drastic editing fails to threaten its integrity. Best practice is to both scan in 16-bit and and edit levels in 16 bit. You need change the file to 8-bit format only for outputting to a printer, or – in the case of Photoshop – to use tools that are unavailable when editing 16-bit files. It’s also wise to archive a 16-bit version of valued images. After all, why ditch all that information when you may well need it again? Connectivity There are three types of interface used by the scanners on test. Older models still use SCSI. In non-SCSI Macs, the use of SCSI scanners requires that a SCSI card be installed. Other scanners use a combination of USB and FireWire, and Macs that have shipped within the past few years contain both USB and FireWire ports. USB is a comparatively slow interface, and is not ideal for the volume and sizes of files that high-end scanning usually entails. FireWire is the best option. Although no faster than SCSI, it works with most modern Macs, although a number provide it only as a paid-for extra. Software
Scanning software is as important as scanning hardware. Historically, such software has been arcane, and required specialist training. Although a little training can never hurt, most people prefer for things to work without the need for head-scratching – so the good news is that most of the current scanning software packages will guide even novices through the scanning process. However, for those who like to lose themselves in complexity, most of the packages offer high-end manual options. LinoColor This was one of the original scanning software packages, but is no longer longer being developed for the Mac (see “So where’s Heidelberg?”, left). For those using Heidelberg scanners, the company’s decision not to develop software for Mac OS X – or any new software at all – isn’t as bad for its customers as it first sounds, for the company has announced that third-party solutions are in the pipeline – which will increase the life-span Heidelberg’s soon-to-be legacy scanners. SilverFast Ai 6 This runs natively in Mac OS X 10.2. At the time of testing, only Microtek’s scanners shipped with version 6, although Umax and Epson models bundled with Ai 6 were expected to be available by the end of October (but check before buying). If you’re already using version 5.5 of SilverFast Ai, then the upgrade is only $65 from LaserSoft’s Web site (www.silverfast.com). With Ai 6, LaserSoft has achieved a great balance of automation and high-end control. The level of hand-holding offered by the software is adjustable, meaning you can leave either everything or nothing up to the application. There are too many features to list individually, but one of the most popular will probably be the automatic intelligent dust and scratch removal. In our tests, it did a very good job, as did its grain- and noise-elimination tools. SilverFast can also work with colour depths of up to 48-bit, making it possible to work with true 16-bit images across the workflow (see “8-bit and 16-bit scanning explained”). Binuscan PhotoPerfect This works in a quite different way to SilverFast, with greater emphasis being placed on improving original images than faithfully reproducing them. If a picture is too dark, or has a colour cast, PhotoPerfect can turn it into a better-quality image. One of the ways it does this is by rebuilding the image’s histogram, adding colour information to achieve better results. This is akin to interpolation, only for colour content instead of resolution. In Photoshop, adjusting the histogram of an 8-bit images creates comb-like gaps in it. (See “Fingers of fate” 8). These gaps are caused by Photoshop having to guess at missing information. PhotoPerfect figures out what should be in these gaps, making for an unbroken histogram. Although colour professionals rarely enjoy relinquishing control of colour manipulation, the fact is, PhotoPerfect does a fantastic job – so why not let it? Also, this is a non-destructive process, so you can always return to the original. PhotoPerfect is so good it almost obviates the need for a top-end scanner – yet when it’s paired with one, it makes for an immensely powerful bundle. Driver software Third-party software is generally superior to simpler driver software, but this is not to say that drivers are necessarily inadequate. Umax’s driver software, for example, is very capable, lacking just the level of automation of the LaserSoft and Binuscan’s offerings. Similarly, the Epson TWAIN Pro 2, and Microtek’s ScanWizard, also do almost everything you’d expect of scan software.
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