What Is DPI?
DPI. Three little words that can turn any beautifully creative day into a minor existential crisis. DPI is a technical term for dots per inch. It describes how many individual printed dots fit into one inch of physical space. One inch equals 2.54 centimetres or 25.4 mm. If a printed image is reproduced at 300 DPI, the printer can place up to 300 dots along one inch of the printed dimension. DPI matters because children's book illustrations are usually created for physical reproduction. It describes physical output and relates to the size of an image on paper and the amount of detail available for reproducing that image.
DPI Is Not PPI
DPI is not the same as PPI, which stands for pixels per inch and describes the pixel density of a digital image. Your illustration file is made from pixels. Your printer produces physical dots. They are two different stages of the process.
Why Is 300 DPI So Common?
300 DPI or 400 DPI? I’m sure you’ve heard illustrators talking about both numbers before, usually with a slightly panicked expression. At 300 DPI, an illustration contains enough information printers can work with. It gives printed illustrations a high level of detail without creating unnecessarily enormous files.
If the DPI is too low, the illustration may become blurry or pixelated, which can result in a loss of detail. When you are drawing, make sure that your canvas is set to 300 DPI or higher if that is what the printer requested. Most printing companies require 300 DPI, but if the artwork will be reproduced on something larger, they may ask you for a higher DPI. It is paramount to set DPI before you start drawing. Scaling up the artwork afterwards is rarely the magical solution we all wish it were.
DPI Depends on the Final Printed Size
Picture book sizes are always a bit bigger because of the trimming. As I explained in my other article, trim size is the book's physical size once it has been printed, and bleed is a certain amount of space (3 mm to 5 mm) that extends beyond the trim size. Printers use bleed because trimming is a physical process, and tiny variations can occur. For example, a printer might require 3 mm of bleed on each edge. An illustrator creating a full-page image therefore needs to prepare artwork larger than the final visible page. At 300 DPI, those additional 3 millimetres require additional pixels, which equals roughly 59 additional pixels. That may sound insignificant, yet across a full page and several dozen illustrations, preparing files correctly from the beginning becomes paramount.
You can check DPI in Procreate by going into Actions - Canvas - Canvas Information - Dimensions.
If you have any additional questions, let me know,
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