Professor Designer: Image Resolution

By Tracey Ullom, Designer, CATATILLA Design LLC

Have you ever wondered why an image that you downloaded from a web site looked poor and pixilated when you printed on paper? The reason is rooted in the resolution of the image. 

Resolution refers to the amount of information present in a particular raster image. The information is expressed in pixels—those tiny dots or squares that make up a photographic image. Each pixel is comprised of one color. The amount of pixel information is commonly defined as the number of pixels per square unit of dimension, such as pixels per inch, or ppi. The more pixels present in the inch, the more information the photo has; therefore yielding a higher resolution image.

Tips for Applying This to Everyday Use…

Back to the original question: why are images from the web not appropriate for printing on paper? We illustrate this by looking at two photos from common sources:


Photo #1, an image I photographed using an everyday digital camera on the highest quality setting. (vertical photo)
Photo #2, an image I found online. (horizontal photo)

Caution! Be aware of the owner’s Content License Agreement—unauthorized use may result in fines and penalties.


Original pixel dimensions for each:

Photo #1—Camera Photo: 2304 pixels wide x 3072 pixels tall
Photo #2—Online Photo: 1280 pixels wide x 800 pixels tall

Question: How large can I print these images without sacrificing quality?
Answer: Pixel Width ÷ 300 by Pixel Height ÷ 300 = Your Largest Quality Print Size in inches.

We apply this rule to the two photos:

Camera Photo: 2304 ÷ 300 = 7.68 by 3072 ÷ 300 = 10.24
I can print this photo at 7.68 inches by 10.24 inches—an 8x10 inch print.

Web Photo: 1280 ÷ 300 = 4.27 by 800 ÷ 300 = 2.67
This can be printed as 4 inches by 2.5 inches, roughly. Notice—this is not even a 3x5 inch print!

How to find an image’s pixel dimensions…
Windows – Right Click on image and select “Properties”. The image’s resolution should appear.
Mac – Right click on image and select “Get Info” and the image dimensions should be listed under the “More Info” portion.

How does all this affect design?
The industry standards are:

• WEB = 72 ppi
• PRINT = 300 ppi

The most important thing to understand is that a printed photographic image has very different requirements than an image meant for online viewing. Each requires different color modes, file types, and different levels of image resolution. The best rule of thumb you can follow with images related to your marketing material is to set your camera to the highest possible quality setting and save a copy of the original un-edited image.