Lecture notes

250.03 - Raster Art

Raster | Resolution | File Format | Color Space | Scanning

See: DMT 52-60 raster vs. vector, resolution and file size, color space, file formats, input/output

Raster

Computers generate and output (to screen or to other devices) two primary types of graphics for both still and motion: raster (bitmap) and vector (object oriented).

Raster images are what we would think of as photographic or continuous tone. Vector objects are characterized by broad areas of similar tones, and are more graphic than photographic.

Each graphic type has very specific uses, characteristics, benefits and faults. Many programs now combine both vector and bitmap creation and management to some degree. Understanding the characteristics of each will help you to choose the correct format for your purposes and to optimize your workflow.

Raster (bitmap)

Raster (bitmap) images are made up of individual pixels (picture elements,) the color and shade of which are mapped to a rectangular grid. Painting, imaging and video programs like Adobe Photoshop, Corel Painter and Apple Final Cut Pro primarily generate raster images.

Main characteristics: Bitmap images can reproduce fine quality, continuous tones required for photorealistic or painterly imagery. Pixels can be intuitively smeared as if they were wet and then filtered for special effect. Objects can be blended into one another so that their edges combine.

Limitation: bitmaps are resolution dependent, made to be viewed at a certain physical size. If a bitmap image is enlarged beyond 100% of its original size it will begin to look jagged or pixelated.

Editing: specific groups of pixels must be selected before they can be edited. of becomes necessary. Programs like Adobe Photoshop provide advanced (and sometimes complex) methods of selection and masking so that filters and adjustments can be made to certain areas while non-selected portions remain protected.

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For vector art lecture notes, click here.