Handwritten manuscripts were occasionally illustrated by hand, whether by the same hand as the scribe or by a different artist. As the printing press took over from scribes, the search for a means of illustrating several copies of the same book in an efficient manner began.
The answer came in the form of woodcuts and engravings. Both types of images were formed in similar ways with minor differences that explain the difference in appearance of a finished image.
Woodcuts indicate images that were created from carving counter-relief images into wood blocks following the grain of the wood. Printers then inked the surface of the carving and pressed it into the paper.
Engravings were made by carving the images into wood blocks against the grain of the wood. This allowed for greater detail because the wood was less likely to split or break. In later centuries, engraving would move to copper then steel plates rather than wood.
When looking at an image, it is possible to differentiate between woodcuts and engravings by the style of illustration. Woodcuts are more likely to have greater amounts of white space, or space where no ink is present, and there are fewer levels of shading. This is because lines had to be thicker due to the wood's propensity to split. Engravings could be created with thinner lines without fear of the wood splitting. This allowed for the use of a cross-hatch method for creating varying levels of shading that results in less open white space and the appearance of more shades of gray.
Whichever method a printer chose to use, the illustrations could be inked onto the pages of the book quickly and in immediate succession. This helped streamline the printing process and made books less expensive and more accessible to a wider range of people.
The level of detail possible in woodcuts and engravings is still impressive even in comparison to computer-generated images of modern books.