Fine Print Knowledge Center
The online guide to print and design.
In an optical context, a measure of the ability of input and output devices or of photographic films to visualize two adjacent dots independent of one another.
The resolution depends on the physical properties of the visualizing or recording device or material and is usually limited by the wavelength of the light source.
Resolution is usually given in dots per inch (dpi) or in lines per millimeter.
DPI = “dots per inch” which technically refers to printed resolution, although it has become the industry standard and is often confused with PPI (pixels per inch).
PPI is a relative measurement and before setting it you need to know the physical size of your document. Digital images are composed of pixels, the more you have of them per inch, the finer the detail.
Printing standards have determined that a minimum resolution of 300ppi at actual size is needed for optimal image clarity.
In cases of images with logos or text 400ppi is recommended (although for these types of images, “vector artwork” is highly recommended)