Vector files are the most optimal file types for custom posters and large-scale printing. Raster images can also work if they are 300 ppi at 18" x 24".
Raster images are made up of a bunch of tiny pixels, while vector images are made from mathematical paths and can be infinitely scaled.
• You can upgrade any image to a vector graphic with Redraw.
• You can increase the resolution of a raster image with Upscale.
Vector file types include: eps, ai, pdf, SVG, sketch
Raster file types include: png, jpg, gif, tif, psd
Learn more about the differences between raster and vector artwork here!