Resolution

No, not those horrible New Year’s Resolutions that everyone abandons on Jan 3rd – I’m talking about File Resolution. We frequently get graphic images sent to us that look horrible when put in print. It’s usually about the file resolution. We recommend that your images be 300dpi. “DPI” is a measure of density and stands for “Dots Per Inch”. Yes, I know that we use the metric system but it’s what everyone understands, and if you must know, 300DPI = 118DPC (Dots per Centimeter, sometimes referred to as Pixels Per Centimeter).

But it’s not quite as simple as that I’m afraid. A 6×4 inch photo at 300dpi would only be 150dpi when used as an A4 image (and has different proportions). Dots per inch/centimeter must be seen as a relative measurement – it is relative to the final output size. As we enlarge an image, the dpi will reduce.

Perhaps the most common issue would be with images taken off web sites. Ignoring the possible copyright issues of these, they are usually at 72dpi.  This might be fine if you want to use them smaller than they look on screen, but they can’t be scaled up well at all. An image from a web page that takes up the full 800 pixel width would only be 6.7cm wide at 300dpi.

Our printers print at about 600dpi, although the naked eye can’t really tell the difference between 300 and 600 dpi.  At 150dpi the eye can see that the image is not quite fluid, and at 75 dpi the dots that make up the image start to look squarish and can usually be easily discernible – depending on how close you are to the page.

So our advice is to start with the highest file size and resolution that you can. We can easily scale something down, but we lose quality when we scale it up. If you are purchasing images from an image library don’t just focus on the DPI – look at the total number of pixels and check that it is suitable for your intended size, and then it might pay to purchase the next size up from your immediate needs.  What works well on an A5 flyer is usually not so pretty on an A1 poster (having been magnified by a factor of four – 300dpi goes down to a chunky 75dpi).  There is only so much magic we can work!