Photography Printing Guide - DPI vs PPI

Design215 Photography Printing Guide - DPI vs PPI: "dpi is NOT THE SAME as ppi !!
Even though 'dots per inch' (dpi) and 'pixels per inch' (ppi) are used interchangeably by many, they are not the same thing. Traditional printing methods use patterns of dots to render photographic images on a printed page. While pixels on a monitor are square and in contact with the adjacent pixels, printed dots have space between them to make white, or no space between them to make black. Color photographs are printed using four inks, Cyan, Magenta, Yellow, and Black (CMYK), and four separate dot patterns, one for each ink. Dots per inch (dpi) refers to printed dots and the space between them, while pixels per inch (ppi) refers to the square pixels in a digital image. Keep in mind that many companies will ask for images at 300dpi when they really mean 300ppi."