Answered by Forest Wathen, Prepress Manager, EU Services

Question:
Can you explain the difference between low resolution and high resolution art?

Answer:
The term resolution refers to the sharpness or clarity of an image. When used in the printing industry, it typically refers to the amount of information contained in a scan. Too little information can result in jagged or pixilated images. Too much information will make for large file sizes and not add to the detail of the final image. Resolution can be expressed in many ways but the generic term is dpi (dots per inch). When discussing scanning, a more appropriate term is ppi (pixels per inch) or spi (samples per inch). Hi-res images, usually 300 to 400 ppi are appropriate for offset printing while lo-res images, 72 ppi, are better suited for images intended for monitor display.

A good rule of thumb when scanning for hi-res output is 2 times the output line screening when placed at 100%. Most jobs are printed with screens ranging from 133 lpi (lines per inch) on offset stock to 200 lpi on coated papers. In this case, a scan with a resolution of 400 ppi will cover the higher lpi. Remember, information can be removed from a scan but not added. Always default to a higher resolution.