Unless you’re an 8-bit artist on Pixilart or Aseprite, you’re most likely not looking for noticeable pixelation in your image. Understanding DPI, or dots per inch, and PPI, pixels per inch, is a must for print file setup, when aiming to prevent an unpleasant, blurry image.
Before we start, here is a quick note regarding our use of the term “DPI” over “PPI”. DPI was originally used when digital images were printed with a 1:1 ratio of image pixels to printer “dots”. Today’s technology has changed so that “PPI”, or pixel per inch, is more accurate, however it is still most commonly referred to as “DPI”. Despite being less correct, we’ll use “DPI” because it is more common.
Okay, too much information, I know.
Let’s carry on.
Without getting too technical, pixels (a portmanteau of ‘picture’ and ‘elements’) are the building blocks of a digital image. Here is a representation of a single pixel:
As seen above, a pixel is generally square in shape. Additionally, it can be blank (zero intensity), completely solid (full intensity), or a variable intensity (think of a lightbulb that can be dimmed to different levels of light). Here are nine pixels with varying intensities:
Grouping together thousands of pixels results in an image. With more pixels per inch, pixels become smaller, resulting in a smoother image.
In addition to variable intensity, each pixel can be a color: either red, green, or blue in the RGB color model; or cyan, magenta, yellow, or black in the CMYK color model. Images represented on a computer screen are typically represented in RGB, whereas printed material is represented in CMYK. It is good practice to design in CMYK if you plan on printing your design. With each pixel assigned a color and an intensity, the combination of pixels creates a color image. Our document on RGB vs CMYK has more, if you are giant nerds like us.
DPI stands for “dots per inch” and is exactly that — the ratio of how many pixels can fit within an inch of an image. If your image has a DPI of 8, only 8 pixels will represent every inch of your image. This example image below has a document size, or art-board, of 20 x 12, and having only 8 pixels per inch results in a blurry, pixelated image:
A good way to avoid pixelation is to set up your file with a DPI of 300 or more. Each inch will have 300 pixels, resulting in a clearer looking image. As a matter of fact, 300 is the standard DPI for printed work, and will typically produce an image that is high resolution, or hi-res. Resolution is it's own can of worms, so keep in mind that DPI doesn’t always guarantee a high quality resolution!
Setting your DPI high isn’t a fix-all when it comes to image quality, however. For instance, if you are scanning a newspaper article at a high DPI (say 600 or even 1200 on some scanners), the resulting scan will still only have the same resolution as the original newspaper print itself. In short, if the original file is low-quality, a high DPI won’t fix that. In fact, the result will be a larger-than-necessary file size.
Additionally, it’s important to remember that DPI must be set high before you begin working on your project. You can always make a high resolution file more pixelated by lowering DPI, but the same is not true for making a low resolution file less pixelated. Unless you’re a wizard.
When designing your print file, setting your DPI between 300 and 600, as well as making sure your document’s artboard is sized correctly, will help to ensure quality printing. Check out our other resources on setting up a print file for more information!