What are Raster Images?

Think of a raster like a mosaic: from up close it just looks like a series of squares but from further away from an image forms. Although the pixel grid is not visible, designers add to it when creating graphics in a raster program like Photoshop. Whenever you use the brush tool to create a digital illustration, every brushstroke adds pixels along the brush path—the number of pixels dependent on the size of the Photoshop document and the radius of the brush you are using. When taking a photo or shooting a video, the lens translates the reflected light into tiny coloured pixels that combine to form a realistic digital image.

Because each pixel is designated to a space on the grid, raster images are resolution-dependent. This means that raster images cannot be resized without distortion because the number of pixels is fixed. The more pixels, the higher quality (or resolution) the image is, given that there is more opportunity for colour blending when viewed from a distance. At the same time, fewer pixels means that an image will show up as tiny or will ‘pixelate’ when resized because there are not enough pixels to provide seamless shading.

• Raster images are ideal to use when you want to show the subtleties of colour gradients and shading—for example when you are editing photographs or painting photorealistic illustrations—due to the amount of colour information they can hold.
• You are able to zoom in and edit each pixel for finer editing.
• Many advanced texture effects work best (or only) with raster images.

Cons

• The amount of pixel and colour information means that specific parts of the image can be difficult to isolate without complex masking.
• File sizes tend to be larger than vector formats.
• Raster images have limitations with scalability. For example, a large scale print like a billboard would require a huge file with a high pixel density.
• You have to pre-determine the intended size of your image which makes it hard to adapt if an unexpected change in the project comes up.

Raster File Formats:

• JPG
• GIF
• PNG
• TIFF
• RAW
• PSD

Raster Softwares:

• Photoshop
• After Effects
• Procreate
• Corel Paint-Photo
• GIMP