Photos: the difference between a screen and a printer

Often what makes a good graphic design is the quality of the photography you use. Whether or not you have photos taken specifically for your business or use stock photography, it can transform a website or a brochure design.

However, an image file which is perfectly good for a website is NOT necessarily good for print. People often wrongly assume that if the image they are sending looks fine on their screen then it will look fine when printed. Unfortunately that isn’t always the case.

Digital photos files are made up of pixels – tiny dots of colour which, when viewed from a distance blend into smooth lines. On a screen, a file which is 72dpi (72 dots, or pixels, per inch) will look fine, as screens aren’t that high a resolution. But put that image into a print file and, unless you scale it down to quite a small size it is going to look ragged and ‘pixelated’ – you eye will not be fooled, and you will be able to see the individual pixels. The more dots per inch, therefore, the smaller the dots and the more the eye sees a smooth, professional image.

Print image files therefore need to be much larger (depending on how large they are going to be printed). But how much larger?

Most image files in publications will be 300dpi. This means that if, for example, you want an image to be the full width of an A4 sheet of paper and look ok when it’s printed professionally then it will need to be in the region of 2500 pixels wide. That will translate into an image which is probably at least 1MB in size and possibly much more.

You may print out a low resolution image on a low-resolution desktop printer and it won’t look too bad. But don’t be fooled – that is because, like a low-resolution screen, the pixels are being blended together to fool the eye. Put the same image through a top-end professional printing press and suddenly you will see each individual pixel. Yuck.

So before you send a designer a picture, take a look to see how large it actually is! In Windows Explorer, if you click on an image, a thin grey bar will appear at the bottom of the page telling you the dimensions of the image (in pixels) and the Size (in KB or MB). If it’s only a few hundred KB and/or a few hundred pixels wide, then it may be okay to use in a website, but it’s just not going to work in a flyer, poster or a brochure. You might be able to use it on the back of a business card (because as you shrink the image, so the number of pixels per inch will naturally go up). If in doubt, speak to a professional graphic designer for advice!