The number of DPI you have is like changing the number of Lego bricks you use within a given distance to create something. Imagine you are given a ruler and you have to build a :-) out of Lego bricks. Now you can choose to build that :-) with fewer Lego bricks, or more. If you use more Legos the :-) will look smoother. If you make any mistakes when building, it will be less noticeable when you use more pieces. This is because the mistakes will be lost in the crowd. This example translates very well into digital art.
The lower the resolution you use when you do digital art means you are limiting the number of ‘Legos’ available to you in an inch of space. So 100 dpi means you get 100 different pieces to help you construct a line. 300 dpi means you get 300 dots to help you piece together a shape, a color gradient, or whatever else you are creating. This is why many digital artists work at high resolution and then shrink their work. It lets the computer have more pieces to work with when it shrinks the image. It also does a good job of minimizing mistakes. There are other reasons to begin work at high dpi such as printing, and the speed of loading an image or webpage. Lower quality images are faster to load.
Many of the sites I frequented suggest paper printers (comics and such) use at least 300 dpi for higher-quality images during printing. However, I found on vistaprint.com that T-shirts are a different story. They want a 175 dpi image. So what are some of the key things to remember about page resolution when doing digital artwork? Remember that if you are creating a page’s dimensions using pixels, rather than inches or another concrete measurement, that your resolution dictates how many of those pixels people equal an actual inch when printing. So if you want a page to print at 8 inches in length and your resolution is 300 dpi you need the page length to be set to 2400 pixels. Now if you actually set the resolution to 100 dpi then 800 pixels of page length would be what you need to print it as an 8 inch-long image. If you still had it set to 2400 pixels for page length, you would get an image that is 24 inches long when you try to print it.
This can get confusing. By the way, PPI is pretty much the same thing as DPI. Don’t worry. There are plenty of resources online to help if this was not a good explanation for you. I think I explained it well enough here that I am not going to include links unless people ask for them. Please leave a comment below if you want more information and links to some of the websites I’ve found. Oh, and I’m not being paid to advertise anyone in this blog. I’ve simply used vistaprint.com before and liked the results. Have a good day, dear reader.