DPI (dots per inch) vs PPI (pixels per inch)
DPI and PPI are the same general idea. When you compare DPI vs PPI, you learn they are both a measurement of density that reflects the quality at which an image is being displayed.
Both DPI and PPI are based on the concept that you can take a whole bunch of small pieces to render a much more complicated image. The major difference is one is for a digital image resolution which affects the image quality on your computer screen and the other is for printing or dots of ink. Let’s explore more below.
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What Are Pixels?
To better understand what DPI and PPI mean you first need to have a firm understanding of what pixels are. When referring to digital images a pixel is defined as the smallest controllable element in a digital photo or screen. When you get super close, you can see each tiny square in the image which is comprised of blue, green, and red elements.
On a digital screen, you cannot see these easily, but when zooming into an image on Photoshop they are easier to recognize. When we take a photograph we use RGB mode. Print uses a different model but the same idea. More pixels are usually a good thing because in digital screens or print they will produce cleaner and clearer images.
PPI (pixels per inch) refers to digital media using pixels. Each pixel in digital can be one of 65+ thousand colors, allowing for a lot of flexibility. Have a look at the graphic below to see how changing the PPI changes the detail of the image on your screen between 300 PPI, 72 PPI, and so on. Each difference between PPI means a change in resolution and file size. These tiny dots make up the display on your screen.
When pixel density is around 72-150 pixels per inch as they probably are on your screen you can’t even notice these little squares. Same story when you print a photo with 150-300 pixels per inch. However, the quality or “smoothness” of the image increases as you get a higher density.
If you ever look at a retina display you’ll notice that the higher resolution than an older Apple display. That’s because there are 300+ pixels per inch on a retina display making your display screen much clearer and prettier to look at. Think about the quality of the output of pixels when investing in your next computer screen or camera.
Changing your PPI
There are many programs you can use to change your (PPI pixels per inch) these include popular editing softwares like Photoshop and Lightroom. You can locate the number of pixels listed with the other settings when you open a new document or digital image.
If you want to increase the resolution of an image, you will want to resample it. Resampling simply means you will increase the number of pixels per square inch in your digital image and the software will delete or add pixels to keep a high quality no matter what the final image size is. This is the easiest way to change the PPI.
In Photoshop click Image > Image Size, and then search the “Resample” checkbox and set it to “Preserve Details” so that you can preserve a high-resolution image. When you increase this number, you will be able to print your image to a larger size.
However, whenever possible you should avoid adjusting the PPI to your existing images. This process forces new pixels to be made and computers are not the greatest at seeing images the same way people do. Many times they make errors in your image.
Modern LCD screens use something called sub-pixels. Each is represented by a different color including red, green, and blue or the RGB color model. Combining all these colors together makes white for your screen but the opposite is true for printing, where combining all these colors together makes black. This is important to know because they can be manipulated to create a sharper screen for your viewing pleasure. You may never need to adapt or use sub-pixels, but it’s an interesting thing to be aware of.
The industry standard for printing is exporting an image at 300 PPI. The higher the PPI number typically means the better quality of the printing. Always use PPI when working with digital images and remember that the increase in PPI means an increase in your file size. So only up the PPI when you need to print images with very clear details or textures. PPI is not really important for web images because your monitor determines the pixel density. You will see no difference on your monitor between a 72 PPI image and a 6,000 PPI image.
DPI (dots per inch) refers to the number of printed dots inside one inch of an image that is printed. The size of the image means more DPI is required.
When you are talking about a printed image or DPI, it’s a slightly different story than working with PPI. Working with printers you typically only have 3 or 4 colors. Those colors have to combine to fake more than 65 thousand colors of ink dots that digital displays can display. How do they do it?
It isn’t as pretty, but if you used a magnifying glass to look at your photograph from an inkjet printer you’d see it was using the same methods as this halftone picture. Up close you see something similar to the golf ball picture using pixels, only each dot is made up of yellow, cyan, magenta, and black. Just as you see all the dots in this half-tone photo you would see all the dots from an inkjet with a magnifying glass.
As you back away from each you no longer see the dots but instead, you see the photograph as a smooth composition. Take a few steps away from your computer to see what I mean. The higher DPI ink means picture elements are clearer and you can avoid a pixelated image. Remember the more dots per inch DPI the better the image quality.
DPI Printer Needs
When your image size is larger and needs to be printed, the printer uses DPI (dots per inch) to produce the final product. Laser printers create images from 600 to 2,400 DPI and inkjet printers use a resolution of 300 DPI to 700 DPI.
There is no standard for print size or dot shape. So a higher DPI does not always mean a better print. Magazines typically use 150 DPI whereas newspapers will often use 72 DPI. The best advice is to ask your print shop for help when choosing the right DPI for your printing needs.
PPI vs DPI: Do they Affect Each Other?
Now that you have a better understanding of PPI vs DPI, you may still be wondering what is their actual connection? The best way to understand their connection is to imagine you want to print a 300 PPI image at 600 DPI. Simply divide 600 DPI/ 300 PPI and you have your answer 1 DPI = 1 PPI.
We hope this article cleared up any confusion between PPI vs DPI. The most important thing to remember is PPI refers more to digital screens and cameras and DPI refers more to inkjet printers and the resolution of an image when it’s printed. They can be used interchangeably when you are avoiding low resolution for your digital screen or images.
Pay careful attention to pixel density when making your next investment. If you want to learn even more about using your camera and what all these fancy techniques mean, try our 365 Photography Course. Bite-size lessons to help you better your skills every day!