Using images

You’ve probably seen images referred to as being ‘high res’ or ‘low res’. High resolution and a low resolution images are very different and are used in different ways. They are split based on what the ‘quality’ of the image is.

A high resolution image. This means that the image contains more than 300 dots per inch. If you were to take a magnifying glass and look at a picture on a piece of paper, you can sometimes see the actual dots or specs of colour information that create the image as a whole. The higher the resolution, the harder they are to see. This is because they are tight and concentrated to make a very clear picture.

A low resolution image. A low res image has less than 300 dots per inch. If you took your magnifying glass again, you would see fewer specs of colour in it. This makes the picture very grainy looking because the dots are so much more obvious.

The example here has a hi res image on the left, and a low res image on the right. We’ve enlarged the same portion of the image up by 7 times. This means you can clearly see the DPI or ‘dots’ of information:

Image resolutions 

The low resolution photo on the right is grainy and ‘pixelated’. This means you would not want to print it out or enlarge it any further. For effect we’ve enlarged it many times and as you can see it is now pixelated. The hi res image on the left is much clearer even when enlarged.

But there is a need for low resolution images. Web browsers normally display images at 72 dpi. If web images were at high resolution, it would take several minutes just to download a single image on a webpage. To make sure that webpages load at a reasonable speed, we remove some information and use them at low resolution.

You can always decrease the resolution of an image afterwards. But you can’t increase the resolution. So always take a hi res photo if you can so you can use it later on for webpages and printed works. A rule of thumb is that a photo taken with your camera larger than 1MB in size is probably high res. Anything smaller is probably low res. If you aren’t sure, check with the Communications team who can advise you.

[v1.1 - November 2017]