PPI, DPI & Image Resolution
In online printing, image resolution plays a huge part in the final outcome of your project. Pixels are the building blocks of an image. Every digital image is made up of thousands or even millions of individual pixels. The more pixels contained within an image, the greater the detail and quality.
The number of pixels makes a huge difference in the quality of your image resolution, as shown below.
PPI (pixels per inch) is the number of pixels contained in a digital image. The density of pixels within a digital image refers to the amount of detail in an image, based on the concentration of pixels. This affects the print size of your design and the quality of the output. For an online printer, an image with a higher PPI tends to be higher quality because it has a greater pixel density.
DPI (dots per inch) refers to the resolution value of a physical printer. In other words, it’s the number of ink dots on a printed piece. DPI primarily concerns the print format, not digital. Printers reproduce an image with tiny dots, and the number of dots per inch affects the amount of detail and overall and the quality of the print.
We do not recommend using web graphics for print projects. They are commonly created in 72 or 96 PPI, which is considered low-resolution. At that resolution, they don’t contain the amount of information you’ll need for the final printed piece. At 72 or 96 PPI, you’ll see more pixelation on the final printed piece than is visible when viewing it on a screen.
Image resolution refers to the level of detail in an image. Raster images are composed of a series of pixels, and as mentioned above, the greater the PPI the greater the print quality.
High Resolution Images
The best resolution for printing is 300 PPI with placed images at 100% or smaller. Increasing the size of an image will lower its final PPI. At 300 PPI, an image will appear sharp and crisp. This is considered to be high resolution or high-res.
Low Resolution Images
Images below 200 PPI are considered low resolution or low-res. Low-res images will appear pixelated and blurred after printing even though they might look perfect on your computer screen. This happens because there are not enough pixels per inch to maintain a sharp image.
It’s important to consider how large an image can be while still maintaining its quality and detail. A low-resolution image cannot be made into a high-resolution image – there is no way to add pixels to improve the quality of an image. When in doubt, always work with high-quality images.
For small format jobs such as brochures or booklets, it is recommended that images for print be saved at 300 PPI, as this will help achieve a high-quality print. To calculate the desired file size, multiply the final printed size of the image in inches by 300. For example, if an image is 4” x 6” on the printed page, 4 x 300 by 6 x 300 = 1200 x 1800 resolution.
For online printing services that offer large format jobs like banners and signs, there’s a little more flexibility when it comes to resolution. Line images that are 200 PPI work perfectly. For photographic images on canvas, 100 PPI is considered adequate.
View Image Size in Photoshop
Graphic-editing software such as Photoshop will generally measure an image’s resolution by pixel dimension. To see what your image pixel dimension is, go to Image > Image Size.
This image can be printed up to roughly 8.5″ x 6.5″ at 300 PPI.