There are a handful of topics related to art and design that have the ability to cause even more confusion the more you research them. Your goal is simply to understand a process or technique better, and instead you end up getting lost in a seemingly endless thread of comments with no more understanding than you had before. The topic of Image Resolution, and more specifically DPI vs PPI, is one of these often confusing subjects. So rather than dive right into the murky waters of this topic, we thought it would be helpful to just wade in a bit as there are some good lessons and best practices to learn.
This goal when designing should always be to create high-resolution files, which refers to the sharpness and clarity of an image. However, this can get confusing as resolution can be measured in multiple ways; Pixels Per Inch (PPI) when it comes to computer screens and Dots Per Inch (DPI) when it comes to printer resolution. DPI refers to the density of dots per inch when printing.
Every printer has a different resolution it can handle, and depending on the process the resolution can be changed allowing for different sizes when printing. For example, you may have heard “300 DPI” mentioned when it comes to optimal printing resolutions. Well, this isn’t entirely true especially when dealing with how you view images on a screen. Hopefully the below example featuring work by Madkobra, will help illustrate this. Each of the images seen below are 400×500 pixels. You will notice all three look identical, however the one on the left is 300DPI, middle is 72DPI, and on the right 1DPI. All three files are 400px wide and all three are 152kb in size.
When it comes to screen resolution, 400px wide is 400px wide no matter what the DPI/PPI is set at. This is why many have referred to worrying about DPI as pointless when it comes to sizing digital images, as what is truly important is the actual pixel dimensions. So why deal with DPI at all? Well, there are a few reasons why it’s still good to think about DPI/PPI. For reference, PPI is used in Photoshop and other programs and while it is not directly related to DPI since pixels can technically be printed at any size, PPI is still a method for targeting print size of your works, and that is worth noting here.
If you look again at the example above, while they all have the same pixel dimensions, the PPI denotes different printing targets. The 72DPI has a target of 5.5 x 6.9 inches, the 300DPI a target of 1.3 x 1.6 inches, and the 1DPI a target of 400 x 500 inches. Whoa, but that’s how billboards are printed, with a really low DPI. Depending on the viewing distance the DPI can be lower. This is one of the reasons why it’s still good to think about using a PPI that allows for these changes. Using a high DPI also allows a printer to have more room to adjust, if you should ever want you work printed on billboard for example.
Another reason it’s good to think about PPI, is that you don’t always have exact pixel dimensions to work with. We give you a breakdown of the pixel dimensions for each product, as recommended by the printers, which makes it much easier to deal with. However, with some projects you only have a target print size. So if you’re commissioned to make a design that is going to be 16″ x 20″, it’s a good idea to aim for 300DPI just to be safe. If they only need 150DPI you can always adjust.
If you happen to be given exact pixel dimensions but also a target DPI/PPI, this could be based on a recommendation of the machine the printer is using. There are so many different printing machines, processes, and calibrations, that it’s best to take the recommendation of the printer as their goal is to print your work at an optimal resolution for the setup they have.
So, when creating new designs make them with as many pixels as possible. I also think it’s a good idea to have a high resolution, 200-300DPI, and save this version as your master design file. Keeping a master file will allow you to easily export the recommended size and resolution a printer needs. It’s always better to scale down in size rather than up, especially when you have a target size to to work with, and not exact pixel dimensions.
We hope this helped clear the murky water a bit, and if you find this topic interesting we encourage you to hit the web and do some research. Just remember to bring some swimming gear and a flashlight.
(Banner image: Rainbow Factory by fabric8)