What are the distances required for reading and face recognition?

Ideal distance for reading a book or computer screen is about 12-15 inches (30-40 cm).  Outdoors signage such as street signs can be read from about 10 feet (3 meters) away (the larger the sign the further away you can be). Faces which have been learned by the device can be identified up to 20 feet (6 meters) away.