Image aspects to consider when building your project: DPI, resolution, and file dimensions
Here’s the situation: you have a presentation to give and your graphics had to be printed yesterday to make it on time. Your designer is out on leave and you’re out of options.
So you grab the full-color logo from the website, mock it up with text on a Kinkos computer, add some images of your product from your phone, and send it to the printer. It looked pretty great on the screen, right? So why does the print look like something from a dot-matrix printer? Why does my print look off, and why does Kinkos want me to lose my job?
The answer is actually a number of things, all related to the way your images were constructed: file type, resolution, and image size.
Different formats for different Purposes
With the right lighting, framing, and scene composition, taking a photo with your cell phone or DSLR can create great results. When Digital Cameras create jpegs they use a process called Raster Image Processing that translates what the lense sees into a tightly-packed grid of pixels so close together that they give the illusion of a smooth photograph.
Example: product or magazine photographs, sports photos, etc.
When designers create logos and images for printing they often use programs like Adobe Illustrator or Corel Draw, these programs create resolution-independent vector image files. These programs allow you to place points on an artboard and manipulate a line, and instead of “rendering” it like drawing a line on a piece of paper, the program records the end points and a mathematical representation of the line. This way you can zoom into an image a practically unlimited amount and still find a sharp edge. These image files can be printed nearly anywhere and at any size and retain their look.
Example: Graphics on a U-Haul truck, vinyl decals and banners, bus design elements.
Depending on the actual purpose of your project your printer may specify one format or another, i.e. vinyl graphics are typically vector, where as photo printing usually accepts raster files.
Appropriate Resolution and Image Dimension
Each image file has two parameters that affect its application: resolution and image dimension. Image Resolution is how densely packed the pixels (or points, for traditional printing) of your image are. Traditional resolution for the internet has been 72 pixels per inch (ppi), but you may also encounter 144 ppi, and 300 dpi images (dots per inch, for print purposes).
Image dimension is the actual size an image is displayed to you when printed, opened in Photoshop, etc. This can be a pixel dimension or inches, i.e. a 1024px by 320 px web banner, or an 5.5” by 5.5” photograph.
You can have images with the same dimension but of different resolutions, see below:
(These are a simulacra of how the resolution will appear on a printed page through a consumer-grade printer, not on screen)
The lower your resolution the fewer pixels you have in your image, breaking the illusion of a smooth sharp graphic.
It’s better to have a plan before crunch time
At the end of the day it’s better to have higher-resolution graphics and need to scale down than be stuck with low resolution and be forced to make due. If you work with an image professional they may have even packaged a series of logo variations during a rebranding project, in different file sizes, formats, and even color spaces.
- Logo graphics are best kept in a resolution-independent format like .eps or .pdf, as you can use it for many applications large and small. Your graphic designer should have delivered logo files in both rasterized and resolution-independent formats.
- Image files with a high level of detail are best kept as higher resolution and scaled when appropriate.
- Graphics like banners, vehicle clings, or large-scale photo prints are really dependant on the project and are typically dictated by the printer.
Hopefully next time you have a rapid turn-around you won’t make costly mistakes like in our example. However in the event that a deadline is knocking on your door, the information above should give you all that you need to have that quick dialogue and help build your project right.