Get the Best Print
For hi-def photo-quality printing, images must be around 300 DPI to prevent pixelation.
CHECKING THE RESOLUTION
In Windows right-click the image file > Properties > Details > horizontal and vertical resolution.
For Mac, open the file in Preview, go to Tools in the Top Menu > Show Inspector
Illustrator displays PPI (Pixels per Inch) for resolution. PPI uses two numbers, horizontal and vertical resolution. Just make sure that the smaller of the two is at or above 300 PPI.
To check the resolution of your artwork in Illustrator, click on your image on the canvas or find the image object in the Your Artwork layer in the Layers Menu and look at the Toolbar above the canvas. The PPI is shown at the top.
CHECK THE QUALITY
Usually these resolution measurements are accurate, but sometimes not. Always double check by bringing your image into the Bombsheller Template in Illustrator. Zoom in to 150%. Your image still needs to look crisp at this magnification.
Resizing smaller in Illustrator increases PPI, resizing bigger decreases PPI. Keep an eye on “PPI:” in the toolbar as you transform.
IMPROVING IMAGE QUALITY
You can improve your image quality if it’s too low by up sampling.
Open the image in Photoshop > click the Image menu > Image Size
Increase resolution to no more than double the current number > click Resample Image checkbox > select Bicubic Smoother from the dropdown.
Afterwards, always perform the 150% zoom test in Illustrator.
If your image quality is still too low, workarounds include scaling down and tiling the image, or converting raster images to vector using Live Trace in Illustrator.