Resolution - your essential guide

If you're creating artwork for print, you'll only get decent results if you've got a basic understanding of image resolution. Don't worry, it's actually quite a simple concept - nowhere near as complex as some people seem to think. So stick with me here, I'm going to try to make this as painless as possible...

What is resolution?

As you probably know, when you view a photograph on your computer monitor you're actually looking at a grid of tiny dots or 'pixels'. Similarly, when a photograph is reproduced in print, it is made up of thousands of small dots of ink. Resolution refers to the number of these dots (or pixels) which are squeezed into a given area. The smaller the dot, the more dots you can fit into a horizontal inch, and the sharper an image will appear to the human eye (up to a point).


If you zoom into a photograph on your PC monitor you will be able to see the grid of pixels which make up the image


The grid of dots which make up a printed photograph can be seen using a magnifying glass

The resolution of an image is usually measured in dots per inch (dpi) or pixels per inch (ppi). Essentially dpi and ppi refer to the same thing, it's simply the number of dots or pixels which make up an image.

If you view an image on your computer monitor its resolution will need to be at least 72dpi to appear sharp and clear. A lower resolution will result in large pixels which will be detected by your eye, resulting in a fuzzy or 'pixelated' image. However, if the same image were reproduced on paper using a commercial printing process it would need a resolution of around 300dpi to achieve a sharp result.

A printed image requires a much higher resolution than an on-screen image (4 times greater to be precise). Therefore, just because your image looks sharp and crisp when viewed on-screen, it doesn't mean it will reproduce correctly when printed.


The image above has a resolution of 72dpi.
It looks sharp and crisp when viewed on screen.


If the same 72dpi image were reproduced in print using a commercial printing press, it would appear fuzzy and pixilated. The only way to improve its appearance and increase its resolution would be to reduce the size at which it is reproduced.

Improving the resolution of an image

Unfortunately, the resolution of an image is determined at the time of its creation. You cannot increase the resolution of an existing image. If you 'upsample' an image, i.e. you attempt to increase the resolution of an image, your computer will merely generate extra pixels and guess what colour these should be based upon the characteristics of surrounding pixels. The result is a blurry image with ugly blocks of colour.

The only way to effectively increase the resolution of an image is to reproduce it at a smaller size. Resolution and size are inversely proportional to each other. In other words, if you enlarge the size of an image, you lower its resolution. If you reduce the size of an image, you increase its resolution. You'll have seen this effect whilst zooming in and out of a photograph on your computer screen. Therefore, if your original image is 300dpi and measures 100mm x 100mm its resolution will drop to 150dpi if it's reproduced at 200x200mm.

Your image editing software should provide information as to the size and resolution of your image. You will need to use this information to calculate by how much you can enlarge or reduce the image to achieve a resolution of at least 300dpi.


You can view and adjust the size (dimensions) and resolution of
your image in Photoshopusing the 'image size' box (see above). Most image editing software applications have similar functionality.

Working with images

If you're creating an original image from scratch using image editing software, set up your document to 300dpi and to the dimensions at which the image will be reproduced. For example, if you're creating a background image which will cover the whole of an A4 leaflet, set your document size to A4 (210x297mm) at 300dpi. You could create the image at a larger size or at a resolution higher than 300dpi but this will not increase the quality of reproduction - you will just end up with a bigger file to store on your hard drive.

Image editing software such as Paint.net or Serif PhotoPlus, can be used to create print-ready artwork files incorporating all the elements of your design including images, graphics and text. For best results, the professionals use Adobe Photoshop.

If you're scanning an image, the same rules apply. Adjust the resolution and scan percentage size so that the image you obtain is at least 300dpi at the size it will eventually be reproduced.

Images downloaded from the internet tend to be very low quality - they will have been compressed for fast download and were intended only for viewing on screen (at the risk of repeating myself, remember an image only needs a resolution of around 72dpi for it to view correctly on screen - the same image will need to be 300dpi to reproduce properly in print). Also you could be breaking copyright laws if you use an image without permission. Instead, use a royalty free image library such as istockphoto.com.

Alternatively, use the search box below to search Photos.com for images now!

If you're taking photographs using a digital camera, set it to the highest quality setting and check the size and resolution of your photos within your image editing application to calculate the maximum size that they can be reproduced.

Importing images into other applications

Files created or modified using image editing software can also be imported into a word processor or desktop publishing application. This is particularly useful if your document runs to several pages or contains a lot of text (it's far easier to work with text in a word processor than in an image editor). Text elements created within your word processor or desktop publishing package behave differently to images or text created in an image editing application. Rather then being made up of dots, they are described mathematically as a series of lines and curves. Therefore, you don't need to specify the resolution of your word processing or desktop publishing file - text, lines and boxes created within these applications will always print at maximum resolution.

However, if you import images into a word processsing or desktop publishing application, you will need to ensure that they reproduce at 300dpi. Bear in mind that if you enlarge an image, you reduce its resolution. So if your original image is 300dpi you will not be able to scale its size above 100%.

If you're serious about creating artwork Adobe Creative Suiteprovides all the tools you need including image editing, drawing and desktop publishing software. Highly recommended!