Scan-able lecture

Introduction

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Over the past few years, scanners have gone from being highly technical instruments used by experts, to gadgets used by virtually everyone with a home computer. The most obvious reason for this is price: scanners now start at under £50 – five years ago, you’d be looking at ten times that sum. Retailers now routinely bundle low- to mid-range consumer scanners with new computers as part of extra-value deals. This has put some capable scanners in the hands of millions of home users, so ease of use is paramount. The scanners on test here all fall into the sub-£150 category, and most are claimed to be easy to use. We’ve assessed what bang for your buck each model gives you in terms of features, as well as highlighting technical aspects you should be aware of when choosing a scanner. Interface
Whichever model you choose, it needs to work with your computer. Apple made USB its interface of choice when it launched the iMac three years ago. All the scanners tested here use USB – except Umax’s Astra 6450, which has a faster FireWire connection. If your Mac doesn’t have FireWire, the Astra is not for you. If using a Mac without USB, then you’ll need to change your Mac before buying a new scanner. New resolution
In the past, companies harped on about their “fantastic 24-squillion dots per inch resolution”. Warning: whenever you see a scanner under £150 offering more than 1,200dpi, be sure to check the small print. Though less common today, companies still print interpolated resolutions on the box. Interpolation is when you add dots to an image, so that if you doubled the number of dots in a 300dpi scan, you’d get a document of 600dpi, but without any extra detail. Interpolation is therefore worthless, and any company that quotes interpolated resolution should be avoided. Scanner manufacturers quote two numbers for resolution – horizontal and vertical. Horizontal resolution is the smaller of the two, but the most important. This is because it’s determined by the number of CCDs (Charge Couple Devices) on the scanning head. Vertical resolution is determined by the number of steps the scanner-head makes while scanning a page. It’s no big deal to get a scanner to take more samples as it sweeps the page, but this doesn’t mean better picture quality. Resolution is a valid specification to quote, as long as it isn’t an interpolated figure. But how much do you need for good quality results? Well, for almost everything you’ll be scanning, 300dpi is plenty. At Macworld all the pictures you see in the magazine are 300dpi. The same goes for most other magazines. If printing to an inkjet – regardless of brand – then you’re unlikely to need to go above this, unless enlarging an image. If this is the case, then a resolution of between 600-1,200dpi will be needed. If blowing something up to more than four times its original size, then you may have to look at more expensive scanners. However, before throwing a couple of gees at a high-end flatbed scanner, consider how often you’re likely to be doing ultra high-res work. The chances are, you can survive with a lower-end model and send the odd large-image job to a repro house for pro scanning. Interface
Until recently, the sole reason for buying a consumer scanner would be as part of a desktop-publishing suite. Now, there are far more applications for them – primary among which are scanning images for Web use and scanning documents for OCR (optical character recognition) processing. The rule of thumb with today’s scanners is the more automated, the better. Whether you’re a a Mac guru or rookie, single-button simplicity is still a plus. I may be quite comfortable using professional-level drum scanners, but there’s still no substitute for pressing a button that allows you to scan, crop, size, and send an email with a picture attachment. A scanner with such worthwhile software support and front-panel control buttons is worth paying that bit extra for. The great news is that, because scanners with these features are designed for consumer use, economies of scale mean prices have become encouragingly low. Colour performance
Colour accuracy is always an issue with scanners, and – although less important with low-end models than with the high-end ones used by graphics pros – it still matters. We did come across poor colour accuracy with some of the scanners on test, but this wasn’t a hardware problem, but rather a case of the software trying too hard to be helpful. If you scan a document that comes out looking wrong, check the settings. It’s almost certain that you’ve picked the wrong option, or the settings are set by default to do something else. However, certain hardware specifications do affect colour performance. Bit depth, for example, refers to the amount of colours a scanner can see, but some models scan at a higher bit-depth than others. Most of the scanners tested have a bit-depth of 36, but others use 42-bit colour. However, this is only an internal scale, and the actual bit-depth on output is lower. The theory is that the scanner picks the best colour palette for each scan, giving more detail to an image’s highlights and shadows. Speed
When scanners took 15 minutes per pass, speed was an important issue. But now that most of them can quite comfortably scan an A4 document in under one minute, the time factor is less critical. The Umax Astra 6450 has a FireWire connection that speeds scanning slightly, but shaving a few seconds off is going to impress only the impatient. At least a FireWire connection allows the scanner to work at full speed without any bottleneck. Transparencies
If the reason you’re buying a scanner is to to archive photo- or transparency archives and albums, then you should consider a model that offers a transparency adaptor. But please note, in this roundup, the scanners that include a transparency hood use static light, rather than the moving lamp seen in pro models. The resolution chosen for scanning transparencies must be higher than for reflective images , because – unless using medium-format film – the original image-size is always so small.
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