Working with Image Resolution in Illustrator
Updated: Mar 4, 2019
Within the context of digital artwork, physical dimensions and resolution are not mutually exclusive because the work may be displayed on a screen, printed, or both. So when it comes to the resolution of your artwork, the most important factors are (1) how you plan to use it and (2) desired file size.
Because Illustrator is used to create vector artwork, there is no native resolution. Therefore, exporting artwork at a specific resolution is not especially intuitive. Fortunately, once you decide on your desired resolution, it’s an easy process – you can even export the same artwork at multiple resolutions simultaneously!
(Need help deciding what resolution to use? Read on for a discussion on print resolution and screen resolution.)
In the world of printing, resolution = quality. Resolution is defined by the number of pixels per inch but the term dpi (dots per inch) is still commonly used in the print industry.
Because pixels can describe both physical dimensions and resolution, let’s take a moment to clarify the difference.
In terms of the physical dimensions of printed work, 1 inch = 96 px. So a 10-inch square = 960 x 960 px. If you were to open this image in Photoshop and print it, you would indeed get a 10-inch square but the overall quality would be poor because the resolution is only 96 pixels per inch.
The more pixels you pack into a single inch, the higher the print quality will be. In all cases, higher resolution = larger file size.
In a nutshell, when printing, physical dimensions describe the size of your container and resolution describes how much information you are squeezing into your container.
So now let’s compare some common resolutions with their equivalent print qualities:
72 ppi = 72 dpi (poor print quality)
150 ppi = 150 dpi (medium print quality, often suitable for printing on fabric and other materials that absorb ink)
300 ppi = 300 dpi (good print quality)
Using a print resolution >300 dpi may or may not yield noticeable results depending on multiple factors, including the printer and the material being printed on.
When using a commercial printer or print-on-demand service, it is always recommended to review their requirements regarding file type, size, and resolution before sending.
In the world of screens, resolution = size and quality. This unusual relationship can make exporting for screens tedious and frustrating.
The reason is simple enough. According to the default standard, 1 inch of screen = 72 pixels. For years, we were all trained that images saved for the web should be 72 ppi – no more, no less. But 1 inch on a modern screen does not equal 72. In fact, the number of pixels per inch varies from one device to another.
The situation is further complicated by the various web layouts we encounter, which further affect how images appear across devices. Images may be squeezed to fit into a small container, or cropped, or they may be stretched to fill a container with dimensions that change depending on screen size.
Despite all this, the basics remain unchanged.
On a screen, any screen, 1 px = 1 px. Unlike in printing, pixels on a screen just line up next to each other. All things being equal, the more pixels per inch on the screen, the smaller an image will look on that screen. If the user increases their screen resolution, the image will look smaller still; if they decrease their screen resolution, the image will look larger.
BUT, in this age of responsive web design, all things are generally not equal. In most cases, our content is placed in, and forced to fill, a container that changes size based on device type. Instead of appearing too small, images without adequate resolution are more likely to look distorted or blurry.
Now, the number of actual pixels per inch on any given screen depends on its resolution and physical dimensions. For example, my laptop has a horizontal resolution of 1920 and my screen is 15” wide, giving me a pixel density of 128 ppi. Compare that to my smartphone, which has a horizontal resolution of 1440 and a screen that is around 2.75” wide – more than 500 ppi!
Here’s a general rule of thumb: the larger the screen, the lower the ppi; the smaller the screen, the higher the ppi. And, worldwide, more people will be looking at your artwork on a phone or tablet than will be looking at it on a desktop monitor.
So, how to deal.
Since screen resolution ultimately boils down to size, the real goal is to export your artwork at a size that looks clean and crisp on as many devices as possible. Using Illustrator’s export options, you can easily adjust the scale, width, height, or resolution to export a larger version of your artwork. If your artwork is large and you want to export a smaller version, your best bet is to export at a specific scale, width, or height.
Personally, I usually prefer to export my artwork at 144 or 150 ppi because it bumps up the size just enough to look good on most screens. When I export based on scale, I tend to fuss with it more, which wastes time.
Whenever you’re in doubt about how large or small your artwork needs to be, check out the recommendations posted by each site you plan to upload your artwork to – and be sure to leverage Illustrator’s ability to export multiple versions of each artboard or asset simultaneously to save yourself a load of time.
The importance of signing and watermarking your work:
By now, it should be clear that physical dimensions and resolution are not mutually exclusive – you can increase the resolution of a piece of artwork if you decrease its dimensions by the same factor; likewise, you can increase the dimensions if you decrease the resolution. All you need is Photoshop.
So, always always always sign and watermark your work before you upload it.