Digital Photography for Graphic Communications
Chapter 3 • File Formats and Applications
A digital photo or artwork could end up in a variety of digital file formats, depending upon the image itself and whether it’s placed in a page. Within the graphic communications industry, there are literally dozens of different image file formats that can be created, manipulated, and reproduced. Some file formats are appropriate for print production, while others are best suited for the web and digital media. The more you know about file formats, color spaces, resolution and compression, the greater the opportunity you will have to achieve desirable outcomes with your digital images. In this chapter, we will explore various digital file formats and their attributes associated with them.
File Formats
There are many different file types that a digital image could be; however, when it comes to the content of the image, there are really only two options: vector and bitmap.
| Vector | Bitmapped | |
| Stationary | diagrams, charts, synthetic artwork: type, Adobe Illustrator and CAD files, Photoshop paths, scalable vector graphics (SVG) | photographs, Photoshop images, pixel-based drawings (synthetic artwork), 1-bit tiff files |
| Moving | vector animation: HTML5 tags, CSS3 styles, JavaScript | animated GIF, digital video: Apple iMovie, Adobe Premiere files |
Vector Image Data
Vector images (Table 3-1) are defined mathematically as a series of points, lines, curves, and shapes, with colour fills and strokes. Their advantage is a small file size combined with resolution independence, or the ability to be scaled up without loss of resolution. They are used mostly for charts, diagrams, type, and synthetic artwork, or pictures drawn on the computer. Vector graphics can be created in different color spaces, can combine process and spot colors, contain multicolor vignettes, and even support transparency in some instances. A disadvantage is the lack of realism that comes with photos. Examples are Adobe Illustrator files, Photoshop paths, and type faces.
Animations can also be vector graphics in the form of HTML tags and accompanying CSS styles and JavaScript interactivity.
Bitmapped Image Data
A bitmap is often compared with a mosaic because it consists of a matrix of microscopic squares that contain tone and colour information to reproduce a photo. Bitmapped images are end-use dependent, meaning the resolution must be set for the desired output, including type and resolution of output, as well as reproduction size.
Resolution for Screen Viewing. The proper resolution for a bitmap image is dependent on the end-use of the image, as well as the scale at which it is to be used. For digital applications, such as websites, the image resolution usually does not have to exceed 72 ppi (pixels per inch) at the size it is being viewed at. The reason for this is that most conventional computer monitors display information at 72 pixels per inch. It should be noted, however, with adva