Ever had a graphic designer say they can’t use an image you have supplied, every wondered why, continue reading and we will explain.
Often, we can’t use images that have been supplied because they are too low resolution, meaning when we rescale the image it pixelates, becomes the quality breaks up and doesn’t look good at all.
This is to do with image resolution. We measure image resolution in PPI or DPI.
- Pixels per inch (PPI), refers both to the fixed number of pixels that a screen can display and the density of pixels within a digital image.
- Dots per inch (DPI), refers to the resolution value of a physical printed image.
What is the difference between PPI and DPI?
PPI describes the resolution in pixels of a digital image whereas DPI describes the amount of ink dots on a printed image.
The “image resolution” corresponds to the number of pixels contained per inch (1 inch = 2,54 cm) and is expressed in DPI (= dot per inch) when physically printed. The higher the number of pixels/dots, the higher the quantity of information or precision in the image. The standard for a print ready image is 300ppi/dpi.
Web images are commonly created in 72 or 96 ppi, which are considered to be low resolutions image. They’re perfect for the web because they feature smaller file sizes that can load quickly online, but they do not translate well to print.
So why do images pixelate?
When you start to scale up images pixels don’t duplicate they expand meaning the image starts to pixelate because it has been increased beyond 100% meaning there are not enough dots or pixels per inch for the size of the image.
Ta da… We can bend this rule and scale up a little bit but increasing an image by 300% it is definitely going to pixelate!
The general rule is the higher the resolution produces a better printed image quality.
So, when we say we can’t use the image you have supplied, were not trying to wind you up we just don’t want your images to pixelate!