Ever noticed how a photo that looks sharp on your screen can turn out blurry and disappointing in print? Understanding image resolution is key to ensuring your images look great, everywhere. Here are some practical tips for using images effectively for both web and print.
The Basics: What Are Pixels?
Every digital image, from a photo on your phone to a graphic on a website, is made up of thousands of tiny, colored squares: pixels. The total number of pixels determines the "size" of an image, often expressed in dimensions like 1920 x 1080 pixels (width x height). The more pixels an image has, the more detail it can contain.
Resolution for Screens: PPI (Pixels Per Inch)
For digital applications like websites, social media, and presentations (PowerPoint), we talk about PPI (Pixels Per Inch). This value indicates how many pixels are displayed per inch on a screen.
- The Old Standard: 72 PPI is often cited as the standard for web images.
- What Really Matters: For digital media, the absolute pixel dimensions (e.g., 1200 pixels wide) are far more important than the saved PPI value. An image with large dimensions will always appear sharp on a screen, regardless of its PPI setting.
- Rule of Thumb for Digital: Ensure your image is large enough in pixels for its intended use. For a full-width image on a website, a width of at least 1920 pixels is recommended.
Resolution for Print: DPI (Dots Per Inch)
When an image is printed, its pixels are converted into tiny ink dots on paper. Print resolution is measured in DPI (Dots Per Inch): the number of ink dots a printer places per inch.
- The Standard for Quality Print: For sharp, professional-quality print (like brochures, posters, or dissertations), a resolution of 300 DPI is required.
- Why a Higher DPI? A high DPI ensures the ink dots are so close together that the human eye perceives them as a single, smooth, and sharp image. An image with a low DPI (e.g., 72 DPI) will look visibly "pixelated" or blurry when printed.
Practical Guidelines: Which Resolution to Use?
Gebruik onderstaande tabel als leidraad bij het kiezen van de juiste afbeelding voor uw project.
| Application | Required Resolution | Key Considerations |
| Websites, social media, newsletters, PowerPoint | 72 PPI | Focus on pixel dimensions. Keep file sizes small for fast loading times. Use formats like JPG or PNG. |
| Professional print (brochures, flyers, posters, books) | 300 DPI | Always provide the original, high-resolution file to your designer or printer. |
| Standard office printer | Approx. 150 DPI | For a simple internal document, 150 DPI is often sufficient and results in a smaller file size. |
How Do I Check an Image's Resolution?
You can easily check the dimensions and resolution of an image yourself.
- On Windows: Right-click the file > select Properties > go to the Details tab. Here you will see the dimensions in pixels and the resolution in DPI.
- On macOS: Open the image in Preview > go to the Tools menu > select Show Inspector. Under the "General Info" tab (the 'i' icon), you will find the pixel dimensions.
Important: You cannot increase a low-resolution image (e.g., 72 DPI) to 300 DPI without significant quality loss. The computer has to "invent" new pixels, which leads to a blurry or fuzzy result. Always start with a source file that is large enough for your final purpose.
Need Help? Use the Image Bank
The easiest way to ensure you have the right quality is to use the university's Image Bank. All images provided there are high-resolution and suitable for both print and web use.
For any questions, please contact the Visuals Team
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