Scanning & Graphics 101
The process and applications of a scanner are relatively simplistic. It acts and functions much like a copier. It has the same little scanning bar that blinds you if you look into it, and instead of feeding paper (though a rare few do) it transmits the scanned object into your computer and allows you to alter it digitally. In that respect, a scanner can far surpass the average office copier.
Scanning color pictures can be fun, but it’s also very challenging. You may expect to get the same quality and detail as the original, but that’s not always the case.
A critical part of any scan is determining the proper resolution, or dpi (dots per inch) setting. Most scanning software allows you to select from a range of settings, usually between 75-6000 dpi. Of course, individual settings depend on the quality of the scanner you’re using, and technological possibilities are expanding all the time.
Generally speaking, the greater the dpi (or higher the resolution), means a better quality scan. It also means that you’ve created a larger file. A typical 400 dpi color scan can be as large as two megabytes, whereas a 100 dpi black and white scan is somewhere between 50-100 kilobytes. There is also a major difference in the smoothness of color shading. The edges of the scanned picture become more jagged and irregular when using a lower resolution setting.
The advantage to scanning in pictures at a lower resolution is that the files are not as large, and can be easily attached to an e-mail or saved to a floppy disk. A 400 dpi file takes a long time to transfer on a slower machine, and is too large to fit on only a single disk. The disadvantage, however, is that the lower resolution creates a lower quality picture. Photo images found on the Web are usually scanned at 72 dpi. While they look great on your screen, these photos will not print on a color printer very clearly.
Black & White Scanning
In scanning black and white text or photocopies, the concern over resolution is not as great. Whether it’s photos or text, contrast is just as important as resolution. Sometimes you’ll need to darken the black or grays to add contrast against a white background. Adjusting contrast can cause otherwise unnoticeable scratches or particles to appear. Using Photoshop, you can easily increase or decrease contrast once a scan is completed.
Another thing to be aware of is the quality of the original you are scanning. The scanned picture can never be better than it’s original, and you must keep in mind that there are always minor deficiencies, scratches, or other imperfections that will be enhanced by the scan. Keeping the glass on your scanner clean, and double-checking for wrinkles, smears and other debris on the original will usually lead to a high-quality scan.
In scanning different kinds of media, the best thing to do is experiment. Once you have some of the basic principles down, you’ll start to see more and more ways to apply them, and even begin to think of new things you might want to try. Play around with scanning objects other than pictures or documents. Most mid-range scanners can capture almost anything that will fit on the glass. Just keep trying different things and don’t get discouraged if success is slow to come. Proper scanning techniques can take years to refine.
So Now What To Do With it?
Computer graphics can be created as either raster or vector images. Raster graphics are bitmaps. A bitmap is a grid of individual pixels that collectively compose an image. Raster graphics render images as a collection of countless tiny squares. Each square, or pixel, is coded in a specific hue or shade. Individually, these pixels are worthless. Together, they’re worth a thousand words.
Raster graphics are best used for non-line art images; specifically digitized photographs, scanned artwork or detailed graphics. Non-line art images are best represented in raster form because these typically include subtle chromatic gradations, undefined lines and shapes, and complex composition.
However, because raster images are pixel-based, they suffer a malady called image degradation. Just like photographic images that get blurry and imprecise when blown up, a raster image gets jagged and rough. Why? Ultimately, when you look close enough, you can begin to see the individual pixels that comprise the image. Hence, your raster-based image of Wayne Newton, magnified to 1000%, becomes bitmapped before you can isolate that ravenous glint in his eye. Although raster images can be scaled down more easily, smaller versions often appear less crisp or “softer” than the original.
To maximize the quality of a raster image, you must keep in mind that the raster format is resolution-specific — meaning that raster images are defined and displayed at one specific resolution. Resolution in raster graphics is measured in dpi, or dots per inch. The higher the dpi, the better the resolution. Remember also that the resolution you actually observe on any output device is not a function of the file’s own internal specifications, but the output capacity of the device itself. Thus, high resolution images should only be used if your equipment has the capability to display them at high resolution.
Better resolution, however, comes at a price. Just as raster files are significantly larger than comparable vector files, high resolution raster files are significantly larger than low resolution raster files. Overall, as compared to vector graphics, raster graphics are less economical, slower to display and print, less versatile and more unwieldy to work with. Remember though that some images, like photographs, are still best displayed in raster format. Common raster formats include TIFF, JPEG, GIF, PCX and BMP files. Despite its shortcomings, raster format is still the Web standard — within a few years, however, vector graphics will likely surpass raster graphics in both prevalence and popularity. The PNG format, a hybrid of the vector/raster worlds, is already being used inplace of GIFs and JPGs on many websites.
Unlike pixel-based raster images, vector graphics are based on mathematical formulas that define geometric primitives such as polygons, lines, curves, circles and rectangles. Because vector graphics are composed of true geometric primitives, they are best used to represent more structured images, like line art graphics with flat, uniform colors. Most created images (as opposed to natural images) meet these specifications, including logos, letterhead, and fonts.
Inherently, vector-based graphics are more malleable than raster images — thus, they are much more versatile, flexible and easy to use. The most obvious advantage of vector images over raster graphics is that vector images are quickly and perfectly scalable. There is no upper or lower limit for sizing vector images. Just as the rules of mathematics apply identically to computations involving two-digit numbers or two-hundred-digit numbers, the formulas that govern the rendering of vector images apply identically to graphics of any size.
Further, unlike raster graphics, vector images are not resolution-dependent. Vector images have no fixed intrinsic resolution, rather they display at the resolution capability of whatever output device (monitor, printer) is rendering them. Also, because vector graphics need not memorize the contents of millions of tiny pixels, these files tend to be considerably smaller than their raster counterparts. Overall, vector graphics are more efficient and versatile. Common vector formats include AI, EPS, CGM, PNG, WMF and PICT (Mac).