With the numerous amounts of images to choose from online, it can be overwhelming to determine which file formats to begin with. Do you use raster or vector images?
Raster images are made up of pixels, while vector images are formed by mathematical curves and paths. Being comfortable with the ins and outs of both formats and how they translate when exported is an essential skill for every designer.
If you surf the web, chances are you have seen a raster image. Raster, or bitmap, images consist of tiny squares called pixels. These pixels contain bits of color and when combined, they build images. The more pixels in an image the higher the quality, and vice versa. When you zoom in on an image the pixels become more apparent while the details of the image become blurry.
Notice how the edges of the tropical pattern below become pixelated and jagged when magnified. This is a key indicator of a raster-based image. Obvious pixels make an image look unprofessional and unsightly. As a rule of thumb, it is best to only downsize a raster image to avoid heavy pixelation.
Image via NataliaKo.
Due to the abundance of pixels in a raster image, the file sizes can be substantial. An illustration with higher DPI (dots per inch) or PPI (pixels per inch) will be larger in size and data, which can be worrisome when there are limits to image storage or restrictions on uploaded file sizes.
Tip: You can quickly cut down file size by reducing the resolution to 72 PPI for online posting
When to Use Raster Images
Raster images are used in photography and digital applications. When you take a picture with a phone or a camera the image is recorded as pixel data, and when these images are uploaded online the end result is a raster image. To edit these images you need access to raster-based programs like Adobe Photoshop or Shutterstock Editor. For design work, it is best to use these programs for photography and imagery only; avoid using them to design logos and icons.
File Formats for Raster Images
Raster files are saved in various formats:
.tiff (Tagged Image File Format)
.psd (Adobe Photoshop Document)
.pdf (Portable Document Format)
.jpg (Joint Photographics Expert Group)
.png (Portable Network Graphic)
.gif (Graphics Interchange Format)
.bmp (Bitmap Image File)
While all of these display pixels, each file format has its own distinct display settings. Some files take up additional data and use higher resolutions, while others take up less storage but tend to be lower in resolution and quality.
Vectors use a different approach to image renderings. They are made of paths and curves dictated by mathematical formulas. These paths and curves are produced exclusively through design softwares designed for vectors, like Adobe Illustrator or Sketch. Due to their algorithmic makeup, vectors are infinitely scalable and remain smooth and crisp even when sized up to massive dimensions.
Even when scaled to substantial proportions, this pattern below remains clean and exact. Elements like fonts render the same way: When sized up or down, they retain their quality.
Image via NataliaKo.
A vector image’s formulaic makeup keeps file sizes to a minimum in comparison to its raster counterparts. This comes in handy when there are restrictions to file sizes or image storage. While a vector image file has many advantages, there are compatibility issues when shared. You must have access to vector-based programs in order to edit the native files.
When to Use Vector Images
Programs such as Adobe Illustrator or Sketch are best used to create and manipulate vector images. Avoid raster-based programs such as Adobe Photoshop when incorporating vector elements that need to be scaled.
Vectors’ scalability make them ideal for design work consisting of logos and icons. Both logos and icons require immense details and many size options, usually depending on their application. For example, you might use a logo on something as small as a business card or something as large as a billboard. Vectors are ideal for large or small format prints, because rasterized designs will lose quality when resized.
File Formats for Vector Images
Vector files can be saved or edited in these formats:
.ai (Adobe Illustrator document)
.eps (Encapsulated PostScript)
.svg (Scalable Vector Graphic)
.pdf (Portable Document Format; only when saved from vector programs)