Pixels: Anatomy of an Image
Printing a digital image is the process of turning something digital into something physical. Instead of physical dimensions, digital images have pixels. Pixels are virtual dots that have no set dimension and can be printed at any size.
When we talk about the size of a digital image, we talk about pixels per inch, or ppi. (You'll also see this described as dots per inch, or dpi on our site, but the clearest term is pixels per inch.) The ppi is the number of pixels in a linear inch and is also referred to as the resolution of the image.
The dimensions of an inch do not change, but if you are printing an inch of fabric, the pixels get smaller the more of them you squeeze into the square of physical space:
If you have an image that is 900 pixels wide, it will get smaller as you increase the ppi. At 100 pixels per inch, it would print at nine inches wide. At 300 pixels it would print at three inches wide. At 600 ppi you would get a printed image of only 1.5 inches wide:
Best resolution for Spoonflower
Photographic paper can capture the sharp resolution created by 300 pixels of data in every inch of space. When you are supplying images for paper printing you'll usually be asked to make sure that they are at least 300 ppi.
Fabric fibers, on the other hand, have a lot more bleed and texture than paper does, so there is a limit to how much detail they can hold. You can print at 150 pixels per inch on fabric for most designs and not see a difference between that and 300 ppi. This is handy because it allows you to use smaller files, which are easier to transmit and upload.
The lowest resolution Spoonflower supports is 150 ppi. Images uploaded at a lower resolution, like 72 ppi, will be converted to 150 ppi. This results in compression of the available information and a smaller printed size. If you upload a 300 ppi image, our system converts it to 150 ppi, displaying it at twice the size. You can change the resolution of your uploaded images by using the “change DPI” link or the “smaller” and “bigger” buttons.
See also: How big should my image be?