Google Books just announced that "To date, they've scanned about 150,000 books worldwide from the 16th and 17th centuries, and another 450,000 from the 18th century." "With our growing list of partners, we expect to scan many hundreds of thousands more pre-1800 titles," Google said.
Printing was introduced in the 15th century, but a great flowering of experimentation in typography took place in the 16th and 17th centuries.
"In digitizing books from any century, we try to create clean images with black text and color illustrations on white backgrounds. This helps enhance readability, save storage spaces and serve illustrated pages faster to readers. However, partners, researchers and other readers have frequently asked us to show the older books as they actually appear, for a couple of reasons: First, these books are interesting artifacts. They've changed their appearance over the centuries, and there's a cultural value in viewing them. Second, because of aging and bleed-through, it can be very difficult to display the images as clean text over a white background; in many cases it's actually easier to read the text from the original (what we call "full-color") images."
Below are two examples from 15th century. Books from 16th and 17th century are now available in full-color view in Google Books:
Secunda centuria, das ist das ander Hundert der Evangelischen Wahrheit, Johann Nass, 1568:
Thargum, hoc est, Paraphrasis Onkeli Chaldaica in sacra Biblia : ex Chaldaeo, Paul Fagius, 1546:
[Source: Google Books]