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A picture truly is often worth a thousand words. When trying to explain something to students, how often do you reach for a paper and pencil or go to the blackboard? Often a quick sketch or outline can be just the thing to get the point across. When thinking about content for your course site, consider whether visuals would enhance your narrative: Do you find yourself wishing for a virtual pad and pencil? Could you better represent the concepts if you had supporting illustrations? Do you have photographs to accompany descriptive texts? Or are images the focus of your site?
About Web images
The best part of Web imaging is that, in contrast with print publishing, there is no economic penalty for using images — in full color, no less — and the number of images you publish is limited only by your time and server space. And color reproduced on the computer screen is true color, whereas color in print is simulated, typically through a four-color process. Color images on the monitor are more vibrant because the color shines out from the screen, whereas color on the printed page receives its intensity from reflected light. On the down side, because every monitor is different, images that look great on your monitor may look dark or washed out on another.
The biggest drawback of screen images is resolution: both the spatial dimensions of the screen and the low resolution of computer monitors. Computer monitors are oriented horizontally, with a 4:3 ratio (640 x 480, 800 x 600, 1024 x 768). This fixed proportion can be extremely limiting if you think of the screen as a canvas: imagine Henri Matisse having only one size canvas to work on, and then only in landscape orientation.
The horizontal aspect of the screen presents design challenges, particularly when displaying vertical images.
In addition, images must share the screen with such other page elements as text and navigation links.
In addition to displaying within the limited size and aspect of the standard computer monitor, content images must share the screen with site graphics and navigation links.
Added to spatial restrictions is the fact that the resolution of the computer monitor is coarse in comparison with printed materials. Put simply, this means that there are fewer sample points available to represent an image on screen than in print.
The pixel grid of the computer screen is much coarser than the halftone grid of printed images, which means there are fewer samples available to represent an image.
As a result, images that require sharp detail in order to be understood, such as a lever on a piece of equipment or the fine outlines of a sketch, don't fare well onscreen.
Given these drawbacks, designing meaningful images for the screen can be a challenge. If you scale an image to fit the screen, you may not be able to show enough detail for the image to be useful. If you leave your image large so that the details are clear, you force users to scroll to see it all. As you gather images for your Web site, keep these limitations in mind. Choose images that fit comfortably within your page design and that do not rely on fine details to be understood. And don't get discouraged: although it may seem limited in many ways, the Web is still a great way to get images into the hands (or onto the screens) of your students.
Image sources
Images for your site may already be in digital format — online, on CDs, or as digital photos — or they may be in an analog format, such as a book or videotape, and need to be converted. Several methods for acquiring images for use on your site follow.
Shooting original photographs
Shooting your own photographs is an ideal way to get visual content for your course Web site. That way, you own rights to the images and can customize them to fit your pedagogical needs.
If you are taking photographs for use on your course Web site, shoot with the screen in mind. Take close shots, omitting unnecessary background detail. If your subject is too detailed — the ceiling of the Sistine Chapel, for example — consider shooting a series of close shots rather than trying to represent the subject with a single image. And shoot horizontal shots whenever possible to make best use of the 4:3 proportions of the computer display.
35mm camera
When you shoot images using a film camera, you will need to convert the images to digital files for Web use. It's a good idea to determine what method you will use before you take photographs for Web use (see Scanning and Photo CD, below). Whenever possible, scan from slides or film negatives: it's easier and yields better quality images than scanning from prints.
Digital camera
A digital camera has many benefits for Web site projects. Images can be transferred directly from camera to computer: no film, no developing costs, no delays. However, only high-end digital cameras take images whose quality rivals that of images shot on film. The low resolution and compression used by the low-priced cameras produce inferior images, and any manipulation you do — adjusting color, scaling, sharpening — will emphasize the flaws.
On the other hand, the computer screen is a low-resolution medium, so the imperfections in a low-quality digital image may be less obvious on a Web page than in a printed document, particularly if you limit your modifications to the image. If you plan to shoot your own images for Web use, consider using a digital camera. For many projects, the convenience of having images in digital format outweighs any compromises in image quality.
Use the highest quality settings available on your camera. Even if the files are large, you will have more data to work with and fewer compression artifacts to work around. And keep in mind the points outlined in About Web images, above: shoot closeups against a simple background whenever possible.
Scanning
One way to get images for Web use is to scan them using an image scanner. The scanning process converts an image's color samples to pixels, creating a computer reproduction that you can manipulate and save for use on your Web page. You can scan images from such sources as books, slides, postcards, and other printed media. You can even scan objects as long as they fit on the glass top of the scanner, for example, pottery shards or fabric swatches.
When scanning photographs or artwork for your Web pages, set the dimensions to roughly the size you will want on your Web page. Scan the image at medium resolution, about 133–150 pixels per inch (ppi), especially if you plan to modify the image. Though the final resolution on your Web page will be 72 ppi, you should scan at a higher resolution and then reduce the resolution after working with the image. Save the scans in an uncompressed format such as Photoshop or using non-lossy compression such as TIFF (Tagged Image File Format), and always keep your original scans.
Photo CD
If you have many images for your Web site and some money to spend, consider making a Photo CD. Photo CD is an imaging service developed by Kodak. To use the service, you send your negatives, slides, or unprocessed film to a Photo CD service provider (check the Kodak Web site to locate a service bureau near you). The service bureau performs high-quality scanning and transfers the scans directly to compact disc, then returns your original images along with the CD containing three resolutions of each image and a printed guide with thumbnails, or small versions, of the images on the disc.
Photo CD is a feasible alternative to do-it-yourself scanning, particularly for projects that involve many images. The cost is reasonable — ($1–5 per image), the quality is better than that of a homemade scan, and the convenience is unquestionable. Photo CD is particularly useful when creating virtual reality sequences such as QuickTime VR panoramas or object models.
Note that many film processing companies can produce computer files of your images when developing film. This consumer-level service provides less quality and fewer options than Photo CD, but it also costs much less. The company will post your images on the Web for you to view and download or send you the files on disk along with your prints.
Images for purchase
Several companies sell royalty-free images or image licenses, either as a collection on CD or on a per-image basis via the Web. For most Web authors, the online purchase option is the more practical of the two. When purchasing a CD, you purchase a collection of images — say, "business and industry" or "health care" — of which only a handful of images may be germane to your subject. Online purchase enables you to purchase only the images you wish to use, and you can select, purchase, and begin using an image within minutes.
To purchase an image online, you search the collection for images that match your search criteria: for example, you may want images of the Parthenon, so you enter "parthenon" as your search term. You browse thumbnails of the images that match your search, mark those you wish to purchase, enter billing information, and then download the images. Many sites allow you to download low-resolution complimentary images to try out before making your purchase. The cost per image can run from a couple of dollars to several hundred, but most services offer low resolution images licensed for Web use for about $20–40 per image.
Images from video
Video scanning is a method for capturing still frames from video for use as still images. This setup requires a video player — VHS deck, video camera, digital video camera — hooked to a computer with some sort of facility for video capture. In the capture process, video from the player is fed by cable to the computer's video input. You can then use software to capture individual video frames.
Images from video are of lower quality than those from a still camera. Video resolution is inherently low, and video also has a characteristic called interlacing that, though practical for video, does not work well for still images. With interlacing, the television picture is updated 60 times a second, but only every other horizontal line of the image is displayed at each update. Together these alternating frames make 30 whole frames per second. Although interlacing speeds up the display of TV video, the consequence for still images is that, because a still frame is really two blended fields, the "interlacing artifacts" that we scarcely notice on TV are glaring in a still video image.
Interlacing artifacts can be a problem when capturing still images from video. The alternating fields are most noticable when there is motion in the video, as here with John Kemeny's gesturing hand.
Although video scanning has its challenges, video remains a rich source for still imagery. To get the best images possible, always use the highest resolution and quality available on your hardware. A messy video grab will sometimes improve if you scale the image (make the image smaller) using image editing software such as Photoshop. You can also use Photoshop to sharpen the image (remove blur) and correct interlacing artifacts using the de-interlace filter.
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From Web Teaching Guide
Copyright 2000 Sarah Horton
Added: 15 April 2002