Sometimes, the problem with an image isn't its resolution or the format it's been saved as. If you've printed something that was once pristine but is now looking less than stellar, you probably want answers, stat.
Your original image could very well be enormous and rich, but if your printer is not allocating the data optimally as it prints out the document, you might find it stretched out, compressed, or distorted.
Bridging the gap between the digital image and how you would like for it to look on paper is easy with the help of something called DPI. The same goes for the opposite: DPI is extraordinarily important when scanning photos and documents to a digital file, in service of a more granular, detailed final product.
What Is DPI?
Some conflate the term "resolution", or PPI (pixels per inch), with DPI, and, while the two are related, there are a few key differences. DPI, short for Dots Per Inch, is actually a measure of something called print resolution.
When a printer creates a physical copy of an image, it does not stamp out the document like a printing press. Instead, it uses the digital blueprint of the bitmap document, laying down millions of tiny pinpricks of ink wherever the document says there should be tone.
Picture a square, one inch along all four sides. When a printer prints out this shape, the number of tiny dots of ink it takes to finish the job will be the DPI that the printer has been set to.
Applications of DPI
The most immediately obvious application of DPI is in a print setting—digital printing, screenprinting, any type of printing that takes an electronic image and translates it to some physical medium, such as paper or fabric.
Scanning is another area where DPI plays a critical role. Instead of specifying the number of dots the system is putting out onto a piece of paper, DPI is the number of points of data that your scanner and computer are pulling from a physical image.
Don't confuse this concept with mouse DPI. DPI for gaming refers to the relationship between the physical distance that your mouse moves and the distance that the cursor travels on-screen.
What Is the Correct Print Resolution DPI for Your Project?
While there is no DPI setting that will suit every occasion, the general consensus is that a 300 DPI will pretty much have you covered when printing to a relatively small physical format, such as ordinary printer paper. 300 PPI is the absolute baseline for high-resolution photos, especially if you're looking for something rich and glossy.
So what if you're just printing paragraphs of text for a school assignment? The lazy answer to that would be "who cares?", however, you'll at least want your essay to be legible and easy to read.
The default output DPI in Microsoft word is 220 PPI, which does feel suspiciously generous. Your Word document is guaranteed to come out looking slick under these settings, at any rate. Unless you're trying to save on printer ink, 220 PPI should be fine.
If you're scanning photos, drawings, or documents, 300 PPI is, again, the lowest that you should go. If you've got the hard drive space and the time to wait, there is no time like now to ratchet it up to the nines. Scanning images at 600 DPI, 800 DPI, or even 1000 DPI is not unheard of, especially in the world of fine art and scientific imaging.
Photos adapted for use on the web will usually have a 72 DPI, optimized for speedy, on-page consumption. Ideally, the image has already been loaded before the user scrolls down to see it.
For sites like Instagram and Facebook, the smaller and lighter the file, the better. When uploading to platforms like these, you usually have next to no say in the matter, aside from perhaps a little check box requesting that your photo be uploaded in "high quality".
The bottom line: if you're creating media that will never be physically printed, then your display, screen settings, and eye will be the determining factors when choosing DPI arbitrarily. If you're using a high-quality monitor and your image still looks and feels great, there's no need to crank up your DPI to the umpteenth degree.
These minimums are ones that you'll be able to rely on consistently in a general sense, barring any limitations in storage space that you might end up running into. If you do need to reduce the file size of any image, PDF, or multi-media document, you can always tamp down the DPI in order to keep it reasonable and manageable.
How to Find the DPI of a Document
Once you've nailed down what you need to do with your image and where your document needs to go, all that's left to do is to ensure that it meets the standard. If it doesn't, you'll need to change the DPI of the image.
Chances are, you're working on a desktop. There are two simple ways to see the DPI of any image or document on Windows or on a Mac.
How to Find the DPI of an Image on a PC
First, navigate to the folder that you have your document stored in. Once you've found it:
- Right-click on the image or document and select Properties.
- Switch from the General tab to the Details tab.
- Scroll down until you reach two attributes called Horizontal Resolution and Vertical Resolution. They should have identical DPI values. This is the print resolution of your image or project.
How to Find the DPI of an Image on a Mac
The process is pretty much the same for Apple users, with a short detour. Pull up the document in the Finder and then:
- Right-click on the image or document.
- Choose Open With, and then Preview.
- Under the Tools, select Show Inspector. You'll see the Image DPI listed there.
Dots Per Inch: It's All About the Small Stuff
As print media gradually becomes living history, minute concepts like DPI settings sometimes fall to the wayside in common use. If you've got a future in art, design, or imaging in any capacity, this is one tidbit you'll want to take with you. It really does help you make sense of it all, making your work easier and usually higher-quality in appearance.
Photographers, graphic artists, and illustrators all know how important print resolution is. Whether you're scanning and printing digital photos for a living or just kicking it in your off-time for giggles, the correct DPI will help your next project shine.