How to Buy a Scanner
Post #1567 • August 13, 2012, 3:36 PM • 4 Comments
If you're like me, you've been putting off buying a scanner for ages because doing a proper job of it requires copious research, and instead you've been having fruitless political arguments on Facebook with people who think that stridency makes up for a lack of supporting evidence. No more, dear reader—follow along as I bite down and get this done.
Where to Begin
The following is a distillation of the Newegg Learning Center guide to scanners. Newegg deserves your business. I have dealt with them many times, including the two times I built a computer from parts, and have come away a happy customer in each case. Newegg shall be my vendor.
My priority is scanning flat artwork for digital representation and print reproduction. So to be clear, I am in the market for a flatbed scanner, as opposed to a sheet-fed or slide scanner, which are other sorts of creatures. Sheet-feeding is great if you have to scan a lot of 8 1/2 x 11 documents on a regular basis, but not what I need. Some flatbeds claim to be able to scan film and slides using special attachments and settings. Do not believe them. It will end in tragedy.
Another option to consider is an all-in-one device, which combines a flatbed scanner with a sheet-feeder, printer, copier, fax machine, and toaster oven. A couple of these have served me well in the past but the current one, an HP 7280, has developed an interesting problem in which a vertical shadow appears on the output file when I scan in color. And only when I scan in color. Also, I'm limited to an 8 1/2 x 11 bed and would like to go larger. Furthermore, anyone who asks me to send them a fax in 2012 is an idiot. So I have decided on a flatbed, one-in-one-device scanner.
The Joy of Specs
There are two kinds of common image sensors, the CCD (Charge Coupled Device) and the CIS (Contact Image Sensor). CCDs use more power and cost more but they provide better image quality, so I'll favor a CCD scanner.
Resolution is measured in dots per inch, dpi for short. Dpi tells us that a given scanner can translate an inch of your artwork into a certain number of pixels, and higher is better. We need 1200 dpi or higher. You will hardly ever need output at that resolution, but as explained in the guide,
A 600 dpi scan from a 1200 dpi scanner may be better than a scan at the same resolution from a 600 dpi scanner (all else being equal).
Your typical printed output, such as a postcard, is 300 dpi, so we're way ahead of the game here. I probably don't need to go too far above 1200 dpi. I've made 3200 dpi scans on a university-owned machine, which gives you details that you can't see with the naked eye. That's a lot of fun, but the scanner costs more than the trade-in value of my car.
Also note that we're only looking at optical resolution, not interpolated. Interpolated resolution is generated by
algorithms passed over the digital input magic, and we want to evaluate the hardware itself, especially when comparing devices. One more thing to note is that dpi is often presented as a square, say 1200 x 1200 dpi, which gives you a better idea of how the scanner is looking at your artwork. It happens sometimes that interpolation is more effective across one axis than another, giving you a resolution of 1200 x 1600 dpi, for example. This is another reason to stick to thinking about optical resolution, which is constant in both directions.
Bit depth is the amount of information recorded per pixel, and higher is better, as it means that each pixel will have more descriptive data associated with it. Quoth the guide, "24-bit is sufficient under most circumstances and 36-bit is usually more than enough." I'll go with that.
If I wanted to sell my car to buy a scanner, I would consider a measure referred to as Dynamic Range, which is measured in units that correspond to
a logarithmic scale from 0 (white) to 4 (black) magic. On my budget it won't be an issue, and may not even be easy information to come by if I made it one. To simplify further, scanner speed is of no importance.
The Newegg guide upbraids users who don't consider the software that comes with the scanner, but as a Linux user I usually can't run it anyway. My concern is that the scanner is supported by the SANE interface (Scanner Access Now Easy). The SANE Project maintains a list of supported devices. If you're a Windows or Mac user you don't have to think about this.
Research is Hard, Let's Go Shopping
Newegg has a Power Search into which I can plug the above choices. I leave the default choice, "any," for product type, manufacturer, series, color depth (the three choices are 24, 48, and 96, and 24 is probably enough), and interface. I select flatbed model, CCD image sensor, optical resolution of 1200 dpi or higher, and maximum document size of 8.5 x 14 or larger. The results are two versions of the Epson Expression10000, at $2500 and $2700 respectively. Time to make some tradeoffs.
My first is to give up on the CCD sensor. That adds one more result, the Mustek ScanExpress A3 USB 2400 at $223. SANE describes its support as "basic," which isn't great, but the rest of the specs are impressive: 48-bit depth, 2400 x 2400 dpi, and a mighty scanning area of 11.7" x 16.5". Newegg's users have given it a solid rating of four eggs out of five, with eight reviews.
I'll probably go with this, but just for grins, I'll put back the CCD requirement and give up some ground on scanning area, making it 8.5 x 12.3 or higher. That turns up the HP Scanjet G4050 at $189, but Newegg users have given it rating of three eggs, which is a firing offense. When I remove the CCD requirement and take down the scanning area to 8.5 x 11.7, I have sixteen products to choose from ranging from $55 to $2700. The only reason to prefer one of these to the Mustek would be a better rating than the Mustek's four eggs and a lower price. One of them has both: the EPSON Perfection V30 at $70 and five eggs (calculated across 81 reviews, which is fantastic). It has a CCD sensor, 48-bit depth, 4800 dpi, and a USB 2.0 connector, which is faster than vanilla USB. Tempting, but we're back to the document-sized scanning area, and SANE doesn't support it for beans.
So the Mustek it is. I ignore the mental image of a Russian gangster saying the word "mistake" and put in my order with Newegg.