Standard black uses only black ink or toner, whereas rich black uses elements of the other colors within the CMYK color model (Cyan, Magenta, and Yellow).
For example, if you print in black + white (A.K.A. 1-color print), or even standard black on a color print job, the press/printer uses strictly black ink or toner–no other properties from the CMYK color model are used.
But, in color print (A.K.A. 4-color print), a rich black can be produced to create a deeper and more saturated black by also using percentages of cyan, magenta, and yellow.
Considerations When Selecting Black
Legibility: Layering toner to achieve a rich black can affect the printout’s crispness. This is because of a print term called “ghosting,” which results from different layers not lining up exactly in the print registration. If your black properties include small font sizes or thin lines, choose standard black to avoid the blurry remnants of the other layers.
Quality: On screen, black color variations can be difficult to differentiate. However, when printed, rich blacks have a deep tone that pops from the page, while regular black can appear flat, muddy, or dull.
Cost: Standard black uses less ink to print than rich black since there aren’t extra layers of color printed. Less ink = less cost.