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September
2003

Back to the Basics

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PC Alamode editor Clarke Bird recently sent an email out to the columnists who write for this magazine with the preliminary results of a reader survey. Respondents in general where very pleased with the quality of the magazine…and with good reason. There are a wide variety of articles, reviews and commentary; usually there is something that is going to appeal to your specific interest. One of the things that I noticed about the general suggestions part of the survey is that several people asked for some more basic articles that would appeal to ‘newbies,’ or to quote one comment “You need some more articles written for beginners.” This month, I’m going to review some of the basic concepts in digital imaging. 

Computer graphics breaks down into two general areas…Raster Graphics and Vector Graphics. Raster graphics are images that are described by a grid of dots called pixels (a contraction of picture element). The number of pixels in the grid determines the resolution of the image, more pixels generally means more detail and will allow the image to be printed or displayed at a larger size. An insufficient number of pixels in the grid can lead to the stair-stepping effect, also called jaggies or aliasing, which we have all seen (Fig.1). Raster images are generated by digital cameras, scanners, or ‘paint’ programs like Adobe Photoshop and Photoshop Elements, Corel PhotoPaint and Painter, The Gimp or Jasc Paintshop Pro. Common file formats include JPG, TIF, GIF, PSD, PDD, BMP, PCX, Pict and Targa. Typically raster graphics are photographs, scanned images or other continuous tone graphics.

Fig. 1

Vector graphics are a completely different animal. These use mathematical equations to describe an image. Instead of a grid of dots to represent a rectangle, a vector illustration would not the position of the four corner points, the line thickness connecting them and the color of the fill and stroke (Fig. 2). Vector graphics are ‘resolution independent,’ meaning that they will be rendered at the resolution of the device they are out put on. A vector graphic will look good on a business card or a billboard. These graphics are also usually dramatically smaller in file size. Programs that can produce vector graphics include Adobe Illustrator, Corel Draw, and Macromedia Freehand and Flash. Common vector file formats include AI, CDR, and SWF. Vector art is used primarily for illustration and graphic design, photographs can be ‘vectorized’ with an application like Adobe Streamline or any number of autotrace features in illustration programs. This usually gives the image a posterized look (Fig. 3).

Fig. 2

Just to make things confusing, some file formats can contain both raster and vector information. These metafiles can include Adobe’s Portable Document Format (PDF), Encapsulated PostScript (EPS), Windows Metafile (WMF) or Macromedia’s Shockwave or Flash (SWF). These files can contain just vector, just raster or a combination of the two.

Fig. 3

Recent versions of Adobe Photoshop also blur the line between these two kinds of graphics. Photoshop 6 and 7 will allow you to insert vector type and shapes. This allows you to have parts of the image be resolution independent (like text) while the effects and backgrounds are at a fixed resolution. This only works with certain file formats and output devices. It is worth mentioning, but it could be a whole nuther column!

Now, most folks who are doing digital imaging for fun are working with raster graphics. Digital cameras have had a great couple of years and are getting better all the time. Most of these cameras, as well as flatbed and film scanners, come with some sort of software to help you work with your images. If you have read any of my other columns, you already know that I think Adobe Photoshop is the absolute pinnacle of image editing software. Photoshop, now on version 7, lists for about $500. If that kind of price tag is too hefty, and for the home/hobby user it really is, than the next best thing is Adobe Photoshop Elements 2. Elements lists for $89 and is worth at least twice as much! You can often find it bundled with scanners or cameras for an even better deal. 

When we start talking about digital cameras, the topic of megapixels always comes up. Hearing two digital camera users comparing their hardware can sound like gearheads talking about engine sizes. Simply put, one megapixel is a million pixels. A square that is 1,000 pixels tall by 1,000 pixels wide would be one megapixel. The number of megapixels will translate directly to how big you can print the image and how much detail you will capture. For a more complete discussion of digital cameras and megapixels, look at my November (Do Megapixels Matter?) and December 2002 (Buying a Digital Camera) columns (reprinted on my web site at www.graphicsguy.org). 

Once you get into shooting a lot of digital images, you quickly realize that you can have hundreds or thousands of files to wade through. So much so that it can get mind-boggling. Fortunately there is help for this problem as well. Adobe offers the new Adobe Photoshop Album for $49; or if you are lucky enough to be running Mac OS X, download Apple’s iPhoto (www.apple.com/iphoto) for absolutely nothing. Both programs will organize your photo collection, as well as fix some common image problems (like red eye and poor framing), help you share or print your best images, and then backup them up. A program like this is a great way to publish image to your web site without being a hardcore web geek. 

There has been a boom in interest in digital imaging over the past few years. The tools to do some great, creative work have gotten more ubiquitous, less expensive and far easier to use. If you are one of those users trying it out, drop me a line at the address below and let me know some of the things you are interested in reading about. 

Paul Vaughn is a freelance graphic artist, writer and web designer. Everybody was a newbie at some time. If you would like to see the Graphics Guy address a specific topic email Paul Vaughn at paulv@mac.com.

 

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