The combination of graphic design utilizing high resolution images printed at ultra high line screen values defines the photo quality printing process.
When designing for photo quality printing, graphic designers and printers start with high resolution images of 2400 dpi or higher. Traditional full color non-photo quality printing is done from images of 1200 dpi or less. Photo quality printing requires images to contain the most amount of color information possible. The high resolution images used in photo quality printing is saved in a CMYK file format to best utilize either the commercial printing process or inkjet printing photo quality output capabilities. CMYK dots of Cyan (blue), Magenta (red), Yellow, and Black are placed next to each other in specific patterns that trick the eye into seeing millions of colors. Photo quality inkjet printing transfers 4 or more toner colors to the substrate in a single cycle through the printer. In photo quality commercial printing each color of ink is applied separately.
The high resolution photos are printed (or output) at a line screen value of 1200 lines per inch. Traditional full color printing is done at a line screen ranging from 300 to 600 lpi. The resulting photo quality output is apparent to the naked eye and by using a micrometer. The output includes more dots of ink or toner within each square inch output - and - truer color values and hues due to the greater amount of color information stored in the high resolution image or artwork file.
Commercial photo quality printing uses a web or sheet fed press that may consist of multiple units. The file to be printed is imaged directly onto a drum on the press or onto photographic printing plates. The drum or plates transfer ink to the paper. Photo quality printing on a desktop printer usually uses some type of inkjet or laser printer. The inkjet printer has ink cartridges that place the ink directly on the paper. These are self-contained units connected to a computer through cables.