Image Resolution (DPI), does it matter?

YES it does – it’s critical!
Images on screen or in print are made up of individual dots or ‘Pixels’. Each one is a single colour which when used close to other pixels will fool the eye into seeing a continuous image. The resolution of an image is simply the number of pixels for a given area, which is normally described in ‘Pixels Per Inch (PPI)‘ or  ‘Dots Per Inch (DPI)‘. Magazines are generally printed at 300dpi, whereas newspapers are printed at a lower resolution. Which is why when you look at a newspaper the dots in the images are more noticeable (there’s less of them).

The difference between print and screen

As a ‘rule of thumb’ images for screen-work (i.e websites and emails) are required to be around 72dpi. Because this resolution is much lower than that of print, an image which looks perfectly fine on a screen will not look as good when printed at the same size.

It’s easy to see why: An image 720 pixels wide will be 10 inches wide on a 72dpi screen, but it’ll need to be less than 2.5 inches wide when printed at 300dpi to maintain the same image quality. To print it at 10 inches wide you’ll have to enlarge it. This can only mean one thing, you are going to need more dots!

Just make it bigger…

Modern software such as Photoshop can ‘interpolate’ images to enlarge them, but in essence, they still just add pixels of similar colours around the existing ones to create the illusion of a larger resolution image. Therefore there are limits to how good the final image will end up being. In general the larger the resolution and size of the original image, the more it can be enlarged before pixelation starts to become noticeable. This is because there are more dots in the image, so there’s more to work with. However, any image that is enlarged too much will start to look very blurry or pixelated, so do so cautiously.

Key tips

  1. Images intended for print should be a minimum of 300dpi at the actual size you want to print them. If you do not have software that gives you this information, then we’ll be able to advise you.
  2. As a general guide, you should expect that any image you view on screen to be approximately 1/4 the size when printed professionally.
  3. Even if you have access to software that can do so, don’t simply enlarge an image or change its resolution.  It’s better to leave images as they are and get a graphics professional to advise on whether the image should be enlarged.

We can help

If you would like more help on this subject then get in touch. And if you’d like more tips like this sent straight to your inbox sign up to our regular Design Tips emails.

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