Printing a digital image is the process of turning something digital into something physical, and the method of measuring a digital image compared to a physical image is a bit different. Instead of physical dimension - inches and centimeters - digital images are measured in pixels. Pixels are the virtual dots displayed on a monitor. They have no set dimension and can be saved at any resolution, or pixels per inch (PPI). Once a design file is printed onto fabric or paper, the pixel is then referred to as a dot. Spoonflower prints your image based upon the dots per inch (DPI) of the file. It is a subtle distinction, but it is good to have a grasp of the topic in order to understand how DPI establishes the print size of your designs.
The physical dimensions of a design file are established by a blending of two variables:
- The number of total pixels in the file - width by height
- The resolution of the image
When discussing units for an image on a screen people say pixels per inch, or PPI. However, once printed into a physical product, the correct term is dots per inch, or DPI. DPI represents the number of pixels that will print within one linear inch. In turn, this determines the dimension - physical size and scale - of the printed design.
Now, this is where it gets a bit "mathy"!
When working in concert, these variables determine the final measurements of the image, and because the dimensions of an inch do not change, the physical size of each printed dot is indirectly proportional to the PPI from the original file. A higher PPI means each printed dot will need to be smaller in order to fit into one inch of space.
All this said, the dimension and resolution of a digital file often exist independently from one another until they are saved with your the file settings. The only limiting factor will be the total number of pixels used to create the initial file or take the original photo.
Let's review two examples to visualize this information:
Above are three different one inch squares (not necessarily to scale). Because these images are digital, they are measured in PPI. The first image is just one pixel by one pixel, or 1 PPI. The second is two by two - alternating white and lavender squares - or 2 PPI. The third is nine by nine, or 9 PPI. When printed, the first would print with one dot, or 1 DPI, while the second and third would be 2 dots, or 2 DPI, and 9 dots, or 9 DPI, respectively. Please note, the DPI measures only one dimension, and it will always be a "square".
The designs that you upload to Spoonflower will likely be larger, so here's a more reasonable example to show how changing the PPI of a digital file relates to file and print dimensions.
Let's assume the image above has 900 pixels worth of information across the width. As you increase the PPI settings, the physical dimensions will decrease. For example, the left image is saved 300 PPI. Its width will be 3" since 900 pixels divided by 300 PPI = 3". If the image is resaved at 600 PPI, as on the right, the displayed image would decrease to 1.5" wide (900 pixels divided by 600 PPI = 1.5").
There are many programs available to create and prepare designs. We share these Design Programs and Resources as a starting point, but the list is far from exhaustive. Each program should have a help section to help you locate, establish and save your settings.
We recommend that you save your design files at the exact physical measurements you want the design tile to print, at the resolution of 150 PPI because once you upload your design it will be sized perfectly. Sizing Your Design is your best resource for specific examples.
People often assume that the higher the resolution, the better the print and upload higher resolution designs. While printing on photographic paper often is best at 300 DPI, at Spoonflower 150 DPI is often the sweet spot. In fact, we are confident enough that we convert every upload to 150 DPI.
It may seem counter-intuitive at first, but there is one important variable to consider:
Fabric is a weave of fiber and threads
This weave limits how much detail fabric can present compared to photographic paper. If the resolution is too high, the printer lays down too many dots per inch, which could lead to a slightly blurry print.
On the other side of resolution, anything under 150 DPI will not produce a solid quality print. Therefore, when a file saved at less than 150 DPI is uploaded, our site will still convert and save it at 150 DPI.
Artists will often save and upload designs with resolution different than 150 DPI and contact us, asking "Why is my design a different size?" Review these examples and read the article Sizing Your Design:
- An artist uploads a file measuring 8" x 10" at 72 PPI. The pixel measurement of this file is 576 x 720. (8" x 72 PPI = 576 pixels, 10" x 72 PPI = 720 pixels). Spoonflower converts this file to 150 DPI, or 3.84" x 4.8" (576 pixels divided by 150 DPI = 3.84", 720 pixels divided by 150 DPI = 4.8")
- If the same artist uploads a file measuring 8" x 10" at 300 DPI, the pixels measure 2400 x 3000. At 150 DPI, the image displays at twice the size, or 16" x 20". (2400 pixels divided by 150 DPI = 16", 3000 pixels divided by 150 DPI = 20"). When this happens, it is possible to adjust the resolution with the “change DPI” button, or the “smaller” and “bigger” buttons.
NOTE: Wallpaper sizing is a bit different since the image must fit across the 24" width of paper. If you choose to print a design on wallpaper, our system will automatically convert the design file to necessary DPI to span 24". If the resolution is not quite enough, we will reduce the size and repeat the image twice, with the width measuring 12 inches. Learn more at Sizing Wallpaper Designs.
See also: Sizing Your Design