How To: Image Resolution
Posted on Thu, Nov 10, 2011
By: CCAH Design Department
Why do designers keep requesting high resolution images—is it important? The importance of resolution can be compared to the importance of flossing one’s teeth. Any dentist will tell you that you should only floss the teeth you want to keep and any designer will tell you that resolution only matters on images you want to see.
Image resolution is measured in dots per inch (dpi).
- For PRINT your images need to be at least 300dpi.
- For WEB your images only need to be 72dpi.
Here are two identical images. The one on the left is 1”x1” at 300dpi. The one on the right is 1”x1” at 72dpi. Since you’re viewing this on a computer screen, they both look crisp and clear…
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| 300 dpi |
72 dpi |
But, if we look a little closer, you can see the difference. Notice how the 72dpi image looks fuzzy and pixilated when enlarged to 3”x3”, but the 300dpi image is still clear.
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| 300 dpi |
72 dpi |
If we zoom in even closer you can see that the one inch square at 72dpi is actually made up of 72 rows of 72 pixels. An image with 300 dots per inch has 300 rows of 300 pixels and therefore a lot more information and detail than the 72dpi image.
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| 72 dpi |
How do I know if the image I want to use is high resolution—is there help?
It’s hard to tell only by the file size (i.e., 415KB, 6MB) if your image is high-res or not, because variables like file type and color information can raise or lower the file size of the image.
Photo editing software like Adobe Photoshop and Microsoft’s Paint.net allows users to identify the resolution of images but it’s best to have a designer check to make sure the image you want to use is high-res early in the design process.
Bonus Tip
On iStock, if you click on the Inches tab you can figure out what size image you’ll need using the dimensions of your image. An 11.6”x8” image at 72dpi will be 2.8”x1.9”. Converted to 300dpi, it will be about a 320% reduction.
So by all means, floss your teeth and make sure that your resolution is accurate!
