Scanners
The flatbed scanner is very much like a copy machine, to the extent that it has a glass plate under a lid, and a moving light that scans across under it. Except that scanners can do great color too, and have more controls possible. And like a copy machine, a flatbed scanner allows you to scan photos, paper documents, books, magazines, large maps, or even 3-dimensional objects (those that don't have a lot of depth, coins for example), etc. It scans very much like a copy machine. But instead of creating another piece of paper like a copy machine does, we instead create an image in memory, which we can do with as we please. We have acquired a digital image, and we can show it on the screen, or write a file and email it, or print it, anything we wish.
We must use software to operate the scanner. Some scanner software can operate by itself, and some cannot. The scanner's software is called a TWAIN driver. A fancy word, it is really just another program, but TWAIN is a software standard that all the scanner manufacturers agree to use, intended so that all image programs can operate all scanners.
The TWAIN driver itself is simply the software provided by the scanner manufacturer to operate the scanner (the user interface), and it is also the interface between the graphics program and the scanner hardware. Twain refers to that separation, now photo editors dont have to know how to operate scanners. The Twain driver will always have another name too, Microtek calls theirs ScanWizard, Umax has two, VistaScan and MagicScan, and HP had a version called DeskScan, and the current is called PrecisionScan. The TWAIN driver comes with the scanner, and knows how to operate this one brand of scanner hardware. Each scanner manufacturer provides their own TWAIN driver for their hardware.
From our human viewpoint, the TWAIN driver ordinarily has the controls that we use to specify the scan; we set the mode (Color or B&W or Line art), we set 100 dpi or 200 dpi resolution, we set the area on the flatbed glass that we wish to scan, and there are controls to help correct the tonal quality and color balance of the scanned image. After the scan completes, the TWAIN driver transfers the image into the image program memory. That is, the new image just appears back in the image program. Then you can tweak the image more, or print it, or save it to a disk file.
Flatbed and Film scanners
Having one of each is a very desirable choice. Flatbed scanners are the best and most versatile choice for photo prints and documents, and they dominate the market now. Older choices included sheet-feeder scanners with page rollers, still seen in some low-end multi-function (fax) units. Hand-held scanners have vanished, the results were not so good. A good digital camera with a closeup lens may be a better handheld scanner (tripod recommended).
The flatbed can scan pages while still attached in the book or magazine, and it can scan portions of documents larger than the scanner bed (like maps). Most scan 8.5 x 11.7 inches (including metric A4 size). A few handle 14 inch legal size documents, and a few are A3 size with a 12x17 inch bed. The table space required is the only disadvantage of a flatbed. The big advantage of a flatbed is that the original lays motionless on the glass bed, it won't move between preview and scan, and there is no risk from any feed rollers. Some have an ADF option (Automatic Document Feeder, for documents, not for photo prints), and some have a Transparent Media Adapter option (TMA) for scanning film or even old glass negatives. However, flatbeds just can't do the tiny 35 mm film size well due to insufficient resolution, and inexpensive scanners don't have the dynamic range to do film well.
A film scanner is extremely desirable for 35 mm film. Film is the first generation original, and the best results come from the original film. The 35 mm film scanners generally provide 2700 to 4000 dpi. 2700 dpi allows printing 8x10 inch prints (9x enlargement of 35 mm film), and 4000 dpi allows even larger prints. There are several 35 mm scanners of various prices, but only three for medium size film, and there are three for 4x5 inch film. A high quality flatbed with TMA can also be used for larger film. The top end units have advantage of sufficient dynamic range for scanning film in a critical way. Your goal may allow accepting less, but dynamic range is an extremely important feature for scanning slides, the more the better. Scanning negatives has lesser equipment requirements than slides.
To scan film on a flatbed, at minimum there should be a lamp built into the flatbed's lid, with the lighted area at a fixed location to allow CCD calibration from that upper lamp. The scanner's firmware knows how turn off the lower lamp and to calibrate the CCD from the upper lamp. The scanner software should have modes for both slides and negatives. But a $200 flatbed is not really a film scanner, and 1200 dpi is insufficient scanning resolution to print 35 mm film full page size. Best results are obtained from a real film scanner. Frankly, while scanning film can give the best results, it does require better equipment, and on an inexpensive flatbed, scanning prints is often the better plan.
Don't get too excited about the separate free 35 mm slide adapters that come with some flatbeds. Customers expect them to actually work, but they may be disappointed in results. They may be better than no image at all, perhaps "fair" but not "good" results. The flatbeds may be great for prints and documents, that is not an issue, and better flatbeds can do film well too, but the free film adapters (simple lamp or mirrors) are not a serious tool. A good toy, more like the prize in the cereal box, and if you see it that way, you may be satisfied for casual results, but these free gadgets are not serious tools.
If you want to print 35 mm slides or negatives to be photo quality at 8x10 inch or A4 or larger, you'll really like a real film scanner, at 2700 dpi or more. These scanners are more expensive, and a bit harder to use (because film exposure varies, but photo prints have already been corrected), but can give substantially better large images than any flatbed. You will surely also want a flatbed for print and document work.
Things you can do with a scanner
Scanning photographs for printing, for web pages, for Windows wallpaper, for emailing images to friends and relatives, images for newsletters or genealogical notebooks, for PowerPoint slides shown at meetings, etc, etc. And since these photos are now digitized, you can use editing software to combine images, create special effects, etc. This is an endless artistic field.
Flatbed scanners are very versatile for about all purposes except one. If wanting a huge image for printing 8x10 inches or A4 size prints on a photo quality printer, then a film scanner is much better. This is a limitation when enlarging the color print itself rather than the scanner, but scanning the original negative or slide is the answer.
Copying documents. Use the flatbed scanner with a laser or inkjet printer as a way to have a good copy machine at home. And unlike a real copy machine, you can use the scanner controls to edit and improve these documents too. A flatbed scanner is particularly versatile, and will allow scanning books and magazines without removing the pages. Some people mention that they scan their important papers and receipts as a way to store them (but frankly, that seems more awkward to me than putting the paper in a file cabinet). But I love having a copy machine at my desk now, it gets lots of use.
Faxing documents with a fax modem. You can fax text files from a word processor of course, but if that text is printed on a piece of paper instead, or maybe in a book or magazine, you can simply scan the paper and fax it too. You fax those scanned images the same way, by "printing" to the fax driver.
OCR - scan documents and use OCR (Optical Character Recognition) software to convert the image back to editable text, suitable for loading into a word processor. Most scanners include free sample OCR software, but for extensive use, you'd probably want to spend $80 for better.
Scan real items - coins, cloth, autumn leaves, the cat, whatever. Scanning fabric or wood boards can make some great textures, used maybe for your web page background, etc. 3D objects to be scanned should be more or less flat, without much visible height, well less than an inch for best sharpness. This is not to say you won't get good results with the doll or teddy bear, but the more distant parts will not be sharp or in focus. Shiny metal objects often cause reflection problems, and rotating the object, or perhaps tilting it slightly to change the angle, is about the only lighting control possible. The scanner certainly cannot replace a camera in every case, but it can do a lot. Lighting and depth are the main problems, where cameras offer much more control.
Scanwiches
