We’ve talked a little before about raster versus vector particularly in relation to your logo files, but it’s not just your logo where the differences matter greatly.
Raster images are made up of tiny squares of information (pixels). The most common types of raster images of photographs but a magazine spread created in Photoshop and saved as a JPG also counts. These images have rich details and allow for very precise editing. However, they are not scaleable.
If you wanted to enlarge a photograph from a 2 x 2.5” image to a poster size, for example, 18 x 24”, your image would be blurry. This is because that small image that might have an acceptable print resolution of 300 ppi (pixel per inch) has an effective resolution of 33 ppi when it’s enlarged.
Why is this important? You may want to consider future image uses before you purchase that web image for posting on social media–might you use it in a print ad, poster or other marketing piece?