"How To" Guides > Printing Images
Printing Quality Photo and Document Digital Images
Dots Per Inch and Inkjet Printers
As described previously, pixels per inch (PPI) of image detail is a more important factor in print quality than dots per inch (DPI) of ink that a printer can lay down on a piece of paper.
This is the case with up-to-date inkjet printers since typical printer DPI ratings now exceed the levels at which the eye can discern a meaningful difference.
Since inkjet photo printers are the most common for non-professional general purpose use, it is useful to understand how they create photo realistic images with a limited number of colors in ink cartridges.
Recall that when a color or gray-scale digital image is captured, the digital file stores information about pixels in millions of color shades. On the other hand, an inkjet printer must blend and transition a limited number of colors to attain the subtleties of a full color image. To render the photo realistic image, a quality inkjet printer places set proportions of multiple dots of available colors of ink within a matrix to best represent the complexity of colors and hues of a given pixel.
For this reason, it is often useful for the inkjet printer to have a dots (of ink) per inch (DPI) capability in excess of the number of pixels per inch being reflected in the printed image.
Clearly, one does not need as many subtleties of color, or dots of varied colored inks, to print in black and white or other images of limited colors.
Tip / Hint:
Assuming that you are using quality inks and paper, the following rules
of thumb apply to desired dots per inch of ink.
■ 300 DPI - Good quality text and
routine documents
■ 600 DPI - Presentation quality printing
■ 1200 DPI - High quality photo printing
■ 1200+ DPI - Perhaps most useful to professionals
Additionally, printer manufacturers have built in adjustments for how their inks and printer technology works best with different types of paper.
With current moderate priced printers, you are normally asked to indicate the type of image you intend to print (photo, text, etc.), the type of paper you are printing on (plain, photo in several varieties, etc.), and the quality of the printing (highest photo quality to draft).
Based on these selections, the printer will use defaults for how many dots per inch of ink to print and how much ink to use. With modern print technology, these defaults will typically serve you well and accurately reflect the pixel information that your digital image file provides.
